chemical and biological health hazards and control

NEBOSH Certificate | Unit NCC1: Managing and Controlling Hazards in Construction Activities

NEBOSH Certificate

C O N T E N T S

Element Title Page

8 Chemical and Biological Health – Hazards and Control

INTRODUCTION __________________________________________________________________ 8–4

FORMS AND CLASSIFICATION OF HAZARDOUS SUBSTANCES _______________________________ 8–5 FORMS OF CHEMICAL AGENTS______________________________________________________________________ 8–5 FORMS OF BIOLOGICAL AGENTS ____________________________________________________________________ 8–6 MAIN CLASSIFICATION OF HAZARDOUS SUBSTANCES ______________________________________________________ 8–7 HEALTH HAZARDS OF AGENTS FOUND IN CONSTRUCTION ___________________________________________________ 8–9

REVISION QUESTIONS ____________________________________________________________ 8–19

RISKS ASSOCIATED WITH HAZARDOUS SUBSTANCES ____________________________________ 8–20 ROUTES OF ENTRY INTO THE BODY _________________________________________________________________ 8–20 SUPERFICIAL AND CELLULAR DEFENCE MECHANISMS _____________________________________________________ 8–21 ASSESSING HEALTH RISKS _______________________________________________________________________ 8–22 SOURCES OF INFORMATION ______________________________________________________________________ 8–22 LIMITATIONS OF INFORMATION IN ASSESSING RISKS TO HEALTH_____________________________________________ 8–26 BASIC SURVEYS FOR HEALTH RISKS_________________________________________________________________ 8–26 SAMPLING TECHNIQUES_________________________________________________________________________ 8–27 STAIN TUBE DETECTORS ________________________________________________________________________ 8–28 PASSIVE SAMPLERS____________________________________________________________________________ 8–30 SMOKE TUBES _______________________________________________________________________________ 8–32 DUST MONITORING EQUIPMENT ___________________________________________________________________ 8–32

WORKPLACE EXPOSURE LIMITS_____________________________________________________ 8–34 MEASURING EXPOSURE IN UNITS __________________________________________________________________ 8–34 WORKPLACE EXPOSURE LIMITS____________________________________________________________________ 8–34 LONG-TERM AND SHORT-TERM LIMITS_______________________________________________________________ 8–35 LIMITATIONS OF EXPOSURE LIMITS_________________________________________________________________ 8–35 PRINCIPLE OF REDUCING EXPOSURE LEVELS ___________________________________________________________ 8–36

ACUTE AND CHRONIC HEALTH EFFECTS_______________________________________________ 8–37 DISTINCTION BETWEEN ACUTE AND CHRONIC HEALTH EFFECTS______________________________________________ 8–37


APPROPRIATE CONTROL MEASURES _________________________________________________ 8–39 DUTY TO PREVENT EXPOSURE_____________________________________________________________________ 8–39 ENSURING WELS ARE NOT EXCEEDED________________________________________________________________ 8–40 METHODS OF CONTROL _________________________________________________________________________ 8–41 OTHER PROTECTIVE EQUIPMENT AND CLOTHING________________________________________________________ 8–50 PERSONAL HYGIENE AND PROTECTION_______________________________________________________________ 8–52 HEALTH SURVEILLANCE _________________________________________________________________________ 8–52 FURTHER CONTROLS FOR CARCINOGENS, ASTHMAGENS AND MUTAGENS________________________________________ 8–54

CONTROL OF HAZARDOUS DUSTS ___________________________________________________ 8–55 CARCINOGENS, MUTAGENS AND ASTHMAGENS _________________________________________________________ 8–55 HAZARDOUS DUSTS ___________________________________________________________________________ 8–56 ASBESTOS __________________________________________________________________________________ 8–60

© RRC Training Element 8: Chemical and Biological Health – Hazards and Control NCC1- 8–1

Unit NCC1: Managing and Controlling Hazards in Construction Activities | NEBOSH Certificate

WASTE DISPOSAL AND CONTROL OF POLLUTION _______________________________________ 8–69 ENVIRONMENTAL ISSUES SPECIFIC TO CONSTRUCTION AND DEMOLITION ACTIVITIES_______________________________ 8–69 WATER POLLUTION____________________________________________________________________________ 8–72 WASTE DISPOSAL _____________________________________________________________________________ 8–73


SUMMARY______________________________________________________________________ 8–78

8

NCC1-8–2 Element 8: Chemical and Biological Health – Hazards and Control © RRC Training


NEBOSH Certificate

Element 8 | Chemical and Biological Health – Hazards

and Control

Learning Outcomes When you have worked through this element and answered the Revision Questions, you should be able to demonstrate understanding of the content through the application of knowledge to familiar and unfamiliar situations. In particular you should be able to:

® Identify the forms of, and classification of, substances hazardous to health to be found on a construction site.

® Explain the factors to be considered when undertaking an assessment of the health risks from substances commonly encountered in construction workplaces.

® Describe the use and limitations of Workplace Exposure Limits including the purpose of long-term and short-term exposure limits.

® Distinguish between acute and chronic health effects.

® Outline appropriate control measures that should be used to reduce the risk of ill-health from exposure to hazardous substances.

® Outline a strategy for the control of hazardous dusts in the construction workplace.

® Outline the basic requirements related to the disposal of waste and effluent (and the control of atmospheric pollution) from construction sites.



INTRODUCTION This element is concerned with the very broad subject of ‘substances hazardous to health’ – primarily in the form of the wide range of chemical and biological agents which are used in work activities or may be present in the workplace. This area of health and safety is subject to detailed control by two important statutory regulations – the Control of Substances Hazardous to Health Regulations 2002 (as amended) (known generally as COSHH) and the Chemicals (Hazard Information and Packaging for Supply) Regulations 2002 (as amended) (known as CHIP). Also of importance are the European Regulation on Registration, Evaluation, Authorisation and Restriction of Chemicals (abbreviated to REACH), the Personal Protective Equipment (PPE) at Work Regulations 1992 (as amended) and the Environmental Protection Act 1990.

The first parts of the element consider the hazards posed by chemical and biological agents, both in terms of the ill-health effects they may produce and the ways in which these may be communicated to those working with the substances. We then go on to look at how information about the risks is provided and the ways in which the presence of such risks in the workplace may be monitored. The last parts of the element are concerned with the ways in which employees and others may be protected from the hazards – firstly in relation to workplace control measures and, in the final section, in relation to the discharge of hazardous substances into the environment.



FORMS AND CLASSIFICATION OF HAZARDOUS SUBSTANCES When we consider chemicals in the workplace, we are not solely concerned with substances and preparations which are used directly in work, such as paints or cleaning materials. We are also concerned with chemicals which arise from the work, such as the dusts or fumes that are given off during a process, such as grinding or heating solid metals.

Forms of Chemical Agents A chemical may be in the form of a substance or a preparation. The distinction between the two forms is very simple:

• A substance is a chemical element or a compound, including any impurities.

• A preparation is a mixture of substances, often with a deliberately proportioned composition.

Chemical substances and preparations exist in a variety of physical states and it is important to understand these, as they affect the way in which chemical hazards arise in the workplace. Note, too, that different forms of the same substance may present different hazards.

• Dusts

Dusts consist of solid particles of varying size and are created by such operations as grinding or sieving of solid materials, controlled detonations and various drying processes. In still atmospheres, dusts tend to settle under gravity and accumulate on surfaces. Where there is turbulence, at least some element of the dust will remain airborne.

• Fibres

Asbestos fibres and other man-made mineral fibres (MMMF) have different characteristics to dust particles. Important dimensions are the length and diameter of the fibre and the length to diameter ratio.

• Fumes

Fumes are fine particulate solids, which are created by condensation from a vapour (see below), very often after a metal has been converted to the molten state. The metallic fume is usually the oxide of the metal and is highly toxic.

• Gases

A gas is a formless chemical which occupies the area in which it is enclosed. Its volume and state can be changed by the combined effect of increased pressure and decreased temperature. There are many toxic gases used in industry, such as chlorine, hydrogen sulphide, etc. Gases used in construction include propane, butane, acetylene and LPG.



• Mists

Mists consist of finely suspended droplets formed by condensation from a gas or the atomising of a liquid or from aerosols. Mists are created by many industrial processes, such as chromium plating, charging lead acid batteries and car paint spraying.

• Vapours

Vapour is the gaseous form of a liquid below its boiling point. There is an equilibrium between the two phases. Heating a liquid causes evaporation. Solids also exist in equilibrium with vapour, hence we can smell them, but in most cases the amount of vapour is negligible.

• Liquids

Many chemicals are supplied and used in the workplace in liquid form. These can vary from relatively harmless cleaning fluids through to highly toxic and corrosive acids and alkalis.

• Aerosol

Fine suspension of solid particles or droplets in a carrier gas.

Forms of Biological Agents Biological hazards relate mainly to illness contracted from exposure to harmful micro-organisms. We are concerned here specifically with biological agents which are directly connected with the work undertaken or which are incidental to it. Examples include the following.

Fungi A fungus is a plant lacking chlorophyll and reproducing by spores. Examples include mushrooms, mould and yeasts. Fungal diseases manifest themselves as an allergic or immune response in the form of asthmatic and/or influenza-type symptoms from inhalation of dust or air contaminated by fungi, such as dry rot in roofs.

Blue-Green Algae Blue-green algae (cyanobacteria) can form under certain environmental conditions, e.g. a long period of warm weather followed by heavy rain and more warm still conditions. They are also associated with conditions of eutrophication, a process of nutrient enrichment, e.g. by phosphates (detergents, fertilisers) and nitrogen (fertilisers, manure), resulting in deoxygenation of water. They can lead to the formation of algal blooms, which can be toxic to humans, e.g. in the form of neuro-toxins, hepatotoxins (which cause liver damage), and can also give rise to contact dermatitis, asthma, eye irritation, abdominal pain, etc. The main routes of entry into the human body are through skin/eye contact and ingestion.

COSHH Regulations will apply to work in or near such algal blooms. Construction activities near rivers, watercourses or reservoirs containing them should be avoided or access to such work environments restricted. The use of appropriate PPE will be required and good personal hygiene practices.

Bacteria A bacterium is any of a large group of single celled, microscopic organisms of various shapes that are often agents of fermentation and putrefaction and that may cause disease. There are many bacteria present in the world, but those that we are concerned with here



are those which may be present because of the particular nature of the work processes themselves. Examples include:

• Legionella – caused by the bacterium Legionella Pneumophila, which may be present given certain conditions in cooling towers, water systems and air-conditioning systems. The bacterium may be spread by sprays of mist from the contaminated water source. It affects the lungs and is deposited in the alveoli, and can be fatal.

• Zoonoses – animal bacterial infections which may be transmitted to people in the course of their working with or near particular animals. On construction sites, those working near rivers, watercourses or sewers are particularly at risk. Common examples of zoonoses include:

− Leptospirosis – contracted by working near sewers or infected watercourses and caused mainly by rats’ urine, although some evidence exists that other animals may also be a cause, e.g. voles and fieldmice. Leptospirosis is a notifiable disease under the Reporting of Injuries, Diseases and Dangerous Occurrences Regulations 1995 (RIDDOR).

− Tetanus – see later in the element.

− Anthrax – a virulent bacterial infection which may occur in those who are in contact with live animals suffering from the disease or, more often, from handling infected animal skins or carcasses.

− Brucellosis – caused by a pathogen contracted from cattle or pigs.

Viruses A virus is a pathogenic agent capable of increasing rapidly inside a living cell. Examples include:

• Hepatitis B

This severe form of jaundice is most common amongst medical staff and refuse disposal operatives as a result of contact with blood or excreta of patients suffering from viral hepatitis or in whom the disease is still in its incubation stage, or from carelessly discarded syringes and other ‘sharps’ in disposable plastic sacks. The disease is normally self-limiting with recovery in about six weeks. In about 5% of cases, chronic infectious hepatitis follows, leading to cirrhosis and possibly death.

• AIDS

Acquired Immune Deficiency Syndrome (AIDS) is caused by the Human Immunodeficiency Virus (HIV) which attacks the immune system by which the human body can resist infections. The virus is found in most body fluids of sufferers and is transmitted by the transference of such infected fluids into the blood of another person. It is, though, a delicate virus and relatively easily destroyed outside the body. It is not easily transmitted and requires direct contact.

Main Classification of Hazardous Substances The CHIP Regulations and the European REACH Regulations (EC 1907/2006) form the foundation of general chemicals regulation. (Note that CHIP is the UK implementation (or “transposition”) of several European Directives; REACH is a European regulation and so must not be transposed – it has legal effect in its own right.) CHIP covers how substances and preparations should be classified for their intrinsic hazards, prescribes packaging requirements, and how hazard information should be communicated to users via labels. REACH, amongst other things, additionally requires hazard communication in the form of



safety data sheets (this requirement was formerly within CHIP). Here we are concerned solely with classification – we shall consider the other points in a later section.

The CHIP Regulations require that all chemicals supplied are assessed as to whether they are hazardous – i.e. inherently dangerous. If they are, the ‘category of danger’ must be identified and a description provided of the hazard (the ‘risk phrase’).

For many common hazardous chemicals, classification has already been carried out and the appropriate categories of danger and risk phrases assigned. These are set out in the CHIP Approved Supply List. However, suppliers of other hazardous substances and preparations must investigate the dangers and carry out the classification before the chemical may be supplied.

Categories of Danger There are three general classifications of hazards, each of which contains a number of such categories:

• Physico-chemical hazards – those that are caused by the intrinsic physical or chemical properties of the substance.

• Toxicological hazards – those that arise from a chemical causing harmful effects to living organisms, which in practice normally means death, injury or adverse effects in humans when ingested, inhaled or absorbed through the skin. Toxic effects may be acute or chronic, local or systemic, and reversible or irreversible.

• Environmental hazards – those that relate to the potential of a chemical to damage one or more environmental compartments (i.e. the air, soil or water, including groundwater).

The categories of danger within each classification are shown in the following table.

Classification of Hazardous Substances

Physico-Chemical Toxicological Environmental

Explosive

Oxidising

Extremely flammable

Highly flammable

Flammable

Very toxic

Toxic

Harmful

Corrosive

Irritant

Sensitising

Carcinogenic

Mutagenic

Toxic for reproduction

Toxic or harmful to aquatic organisms

Long-term effects such as persistence

Toxic to the non-aquatic environment

Dangerous for the ozone layer

The definitions of the categories of danger posed by chemicals within the general toxicology classification are set out below.

• Very Toxic

Very toxic substances and preparations are those that in very low quantities cause death or acute or chronic damage to health when inhaled, swallowed or absorbed via the skin.



• Toxic

Toxic substances and preparations are those that in low quantities cause death or acute or chronic damage to health when inhaled, swallowed or absorbed via the skin.

• Harmful

Harmful substances and preparations are any that may cause death or acute or chronic damage to health when inhaled, swallowed or absorbed through the skin.

• Corrosive

Corrosive substances and preparations are those that may, on contact, destroy living tissues. The following examples of corrosive substances may be encountered in the course of construction work:

− Acids – sulphuric acid and hydrochloric acid in chemical cleaners, e.g. for masonry, brickwork.

− Alkalis – cement, lime or agents used as chemical cleaners.

− Gases and vapours – hydrogen sulphide.

− Vapours – from resins, paints and thinners.

• Irritant

These are non-corrosive substances and preparations which through immediate, prolonged or repeated contact with the skin or mucous membrane may cause inflammation.

• Sensitising

These are substances and preparations that may cause an allergic reaction.

• Carcinogenic

Carcinogenic substances and preparations are those which, if inhaled or ingested or absorbed by the skin, may induce cancer or increase its incidence.

For the purposes of classification under the CHIP Regulations, carcinogens are divided into three categories, Category 1 being substances which are known to be carcinogenic to humans; Category 2 where there is sufficient evidence to provide a strong presumption of human carcinogenicity; and Category 3 where there is concern for humans about carcinogenic effects but the available information is not adequate for making a satisfactory assessment.

Note that, in classifying a particular chemical, the hazards it presents may lie within any or all of the general classifications and more than one class of danger may be identified. Thus, concentrated nitric acid is classified as both oxidising and corrosive, and asbestos is classified as a carcinogen (Category 1) and toxic.

Health Hazards of Agents Found in Construction In this section, we consider a number of toxic chemicals and biological agents and the hazards that they pose, together with the circumstances in which these hazards arise. We also describe the body reaction to entry of these agents, both in respect of the immediate, superficial response and the longer-term cellular defence mechanisms.



Organic Solvents Solvents are corrosive chemicals and are found in many materials used in construction, such as paints, varnishes, adhesives, pesticides, paint removers and cleaning materials. Industrial solvents are often mixtures of various chemicals and found under a wide variety of trade names. The most common hazardous substances in the construction industry are:

• White spirit – in paints, varnishes and cleaning products.

• 1-Butanol – in paints, lacquers, and natural and synthetic resins.

• Solvents such as dichloromethane, toluene, xylene and styrene, which are widely used throughout industry. They are common ingredients in industrial paints, and are used as degreasers and cleaners to remove oils, etc. from metal components. They are also used in many chemical processes.

Solvents cause harm in their liquid form (through skin and eye contact and ingestion) and through the vapours given off (where absorption may be by inhalation or through the eyes). This may result in irritation and inflammation of the skin, eyes and lungs, causing dermatitis, burns and breathing difficulties. Many are narcotics (e.g. toluene) progressively causing drowsiness, nausea and unconsciousness, and some are carcinogenic (e.g. benzene). The immediate effect of absorption may be loss of consciousness resulting from inhaling significant quantities in a short space of time. Long-term exposure can affect the central nervous system, causing memory loss and loss of motor co-ordination (dexterity) skills, as well as causing lung damage.

Sensitisation (see below) may result within certain personnel, especially while using adhesives containing isocyanates, and health surveillance is relevant in this case. Exposure to vapours may also cause headaches, nausea and dizziness, and lead to reduced concentration and impaired dexterity (both of which could lead to further accidents). Long-term exposure to high concentrations of vapours, such as in unventilated, confined spaces, can lead to unconsciousness and even death. The effects can be made worse by drinking alcohol.

In addition, solvents tend to be highly flammable.

The use of solvents in paints and adhesives is gradually being replaced by other less hazardous substances, but their use remains a hazard.

Carbon Dioxide When anything organic is burned, carbon dioxide (CO2) is produced. It is one of the greenhouse gases that absorb heat in the atmosphere, keeping the Earth warm. Road vehicles produce 20% of the UK’s CO2 emissions, and other significant sources are smoke from incinerators.

Carbon dioxide is also formed in the body, and expelled in the air we exhale. However, it acts as a simple asphyxiant on inhalation. This type of asphyxiant does not cause any direct injury to the airway, but displaces air and reduces the oxygen level from its normal 21% to a lower level, depending on the extent of the concentration of the gas. Human life can be supported at levels of less than 21% oxygen, but at 10% a serious condition arises.

The reduction of oxygen in the lungs gives rise to rapid giddiness, chest pains, breathlessness and loss of consciousness. Eventually, the prevention of oxygen transport in the blood may lead to toxaemia and death.

Carbon dioxide is also used industrially in its solid form (freezing point –58ºC). This causes ‘burns’ on contact with skin.



Nitrogen Exposure to oxides of nitrogen (nitrogen oxide and nitrogen dioxide) commonly arises in the construction industry from diesel engine exhaust emissions and from the use of explosives. There is likely to be a local accumulation of these oxides in the construction environment. The UK workplace exposure limits of nitrogen monoxide (nitric oxide, NO) and nitrogen dioxide (NO2) are currently under review. In the meantime, both NO and NO2 were subject to a CHAN (Chemical Hazard Awareness Notice) of 1 ppm (8-hr time-weighted average (TWA)) significantly lower than the previous occupational exposure standards. It is worthy of note that all CHANs have now been suspended (from December 2006).

The partial or complete substitution of the air or flammable atmosphere by an inert gas or relatively inert gas such as nitrogen is a very effective method of explosion prevention. Inerting is normally only considered when the flammable or explosive hazard cannot be eliminated by other means i.e. substitution of flammable material with non-flammable, adjustment of process conditions to ensure substances are below flammable limits. Typical uses are within storage tanks where a material may be above its flashpoint and within reactor systems when excursions into flammable atmospheres may occur. Inert gases are also used to transfer flammable liquids under pressure. Inerting is applicable to enclosed plant, since plant that is substantially open to atmosphere cannot be effectively inerted because the prevailing oxygen concentration is likely to vary.

The major risk associated with use of inerting is that of asphyxiation, particularly in confined spaces. In those events where people are required to enter a confined space, formal management control system in the form of a Permit to Work should be in place so that appropriate precautions and control measures can be implemented. We looked at permit to work systems earlier.

Nitrogen is one of a number of gases that can be used for inerting. Others are carbon dioxide, argon, helium and flue gases.

In most inerting systems a slight positive pressure should be maintained within the enclosed plant to reduce the possibility of air ingress. Inert gases may be generated on site, or via bulk storage of cylinder facilities.

Carbon Monoxide Carbon monoxide (CO) is a colourless, odourless, tasteless gas. It is found in combustion gases such as coal gas, car exhaust, producer gas, blast-furnace gas and water gas.

CO is toxic. It combines with haemoglobin in the blood impairing the transportation of oxygen. Concentrations above 5% cause immediate loss of consciousness, but far more people are killed by exposure to much lower concentrations over a period, typically when a gas-fired heater is used in a poorly ventilated room.

Isocyanates Organic di-isocyanates compounds are used to make adhesives, synthetic rubber, polyurethane paints and lacquers, and quick-drying printing inks. The most important industrial applications are in the manufacture of plastics and paints to make them harden quicker.

These can be problematic in industrial use where the vapours may have severe irritant effects and may be sensitisers. All isocyanates have a very low workplace exposure limit (WEL) – see later in this element.

Immediate irritant effects include inflammation of the mucous membrane of the nose and throat and bronchitis. In most cases, the symptoms and signs clear rapidly after the worker is removed from contact with the isocyanate. However, in many of those who have



shown a quick initial recovery, the symptoms have recurred, often violently, after further contact with even very low concentrations of isocyanate (a condition known as sensitisation). Others are known to suffer from a chronic form of asthma, and asthma caused by di-isocyanates is now a recognised occupational disease qualifying for compensation.

Lead Lead is a soft heavy metal and is relatively inert. Its use dates back to the earliest metal-working technologies, and it was for centuries used in plumbing, a trade which gets its name from the Latin word plumbum meaning lead. However, because of the health hazard this poses, such use has been discontinued, though much lead piping still exists. Lead is still used to some extent in buildings, and can typically be seen on roofs of old churches (though it is often stripped off and sold for its scrap value). It is still used extensively in lead/acid batteries for cars.

Lead compounds have been and still are used as raw materials in manufacturing processes. They can be categorised into:

• Inorganic compounds such as lead oxide (red lead) and lead chromate (chrome yellow) used as pigments, though because of toxicity no longer in paints for domestic use.

• Organic lead which was extensively used as an anti-knock agent in petrol, lead tetraethyl, but is rapidly being replaced again because of health concerns.

Organic lead compounds are far more hazardous to health than the inorganic forms since they are mobile, able to participate in biochemical reactions and pass through the food chain (i.e. the series of organisms which eat one another, culminating in humans at the top of the chain).

Metallic lead in its massive solid state cannot be readily absorbed into the body through any of the normal modes of entry (see later). Inhalation of lead dust, though, does present a significant risk and is the most frequent route by which inorganic lead is absorbed. For organic lead compounds, entry is by inhalation and skin contact, although ingestion as a result of work activities poses a minor risk.

Intoxication by inorganic lead compounds leads to general symptoms related to the gastrointestinal tract, the nervous system and the blood.

• Acute intoxication, resulting in general from inhalation of high concentrations of lead fume or dust, produces nausea, vomiting and headaches. This is often followed by constipation and severe intermittent colic. If the brain becomes affected, then dullness, restlessness, tremor, convulsion or coma may develop.

• When exposure has occurred over long periods and chronic intoxication takes place, other clinical symptoms develop. The classic symptoms are headaches, anaemia, palsy, gastrointestinal problems and the appearance of a blue line on the gums.

The absorption of organic lead can have fatal consequences. Its absorption into the body mainly affects the central nervous system, producing restlessness, a raised level of excitement and talkativeness, muscular twitching and possible delusions, acute and violent mania. These conditions are accompanied by a fall in body temperature and a drop in normal blood pressure. Where the level of intoxication is lower, headaches, vertigo, fatigue, a sense of physical weakness, and insomnia with disturbing dreams are classic symptoms.

Where death is delayed or the absorption is not fatal, extensive damage may occur in the kidneys, liver, pancreas and spleen. A pulmonary oedema (a build-up of fluid in the lungs) could also occur following inhalation.



There is a risk of exposure to lead associated with the following work activities:

• Lead smelting.

• Lead chemical manufacture.

• Lead/acid battery manufacture.

• Shipyards.

• Petrol manufacture and handling.

• Plumbing.

• Painting.

• Welding.

Fibres More than 5 million tonnes of man-made mineral fibre (MMMF) are produced annually in more than 100 factories worldwide with glass fibre products comprising over half of this total.

Most glasswool, rockwool and slag wool is used for thermal and acoustical insulation in the construction industry. Glass filaments are used as textiles and reinforcement materials in plastics. Ceramic fibres are produced for high-temperature insulation and in specialty products.

MMMF products release airborne respirable fibres during production and use. Exposure levels in glasswool production are generally 0.1 respirable fibre/cm3 or less; in rockwool and slagwool production, exposures are somewhat higher.

Higher occupational exposures may occur when MMMF products are used in confined spaces, as in the installation of loose insulation.

Studies on the carcinogenicity of MMMF products have so far been inconclusive. In one study, some small increases in the incidence of lung cancer after 20 years of exposure is thought to be related to the use of formaldehyde adhesives used in the manufacture of MMMF products rather than from the fibres themselves.

There has been no correlation of MMMF use with occurrence of mesothelioma.

Asbestos Because asbestos is a good heat and electricity insulator, it has been commonly used in many applications, e.g. lagging for boilers and pipe-work, asbestos cement sheeting, fire blankets, ropes, yarns and friction products, sprayed applications, e.g. fire-resistant encapsulation of metal girders or insulating boards in buildings, roofing materials, loft and wall insulation, ceiling tiles, panels and textured finishes, gaskets, packing and plugs made of asbestos-containing materials.

The inhalation of asbestos fibres causes incurable respiratory diseases, mainly cancers of the lung and chest lining. The diseases have a long latency period and death occurs 15-60 years after exposure, though the initial symptoms (breathlessness and coughing) can appear sooner.

Three main types of respiratory disease associated with asbestos can be distinguished:

• Asbestosis is formation of scar tissue (fibrosis) in the walls of the alveoli (air sacs) in the lungs, causing thickening and hence slowing the passage of oxygen into the blood, so causing breathlessness on exertion.



• Mesothelioma is a rare and virulent form of cancer that affects the lining of the lungs, the lining around the heart and the lining of the abdomen.

• Lung cancer occurs particularly amongst smokers exposed to asbestos. Fibres protecting the lungs are flattened after inhaling cigarette smoke, so there is less protection against asbestos fibres.

The health effects caused by asbestos are notifiable and related diseases commonly lead to a painful death. All forms of asbestos are classified as Class 1 carcinogens and although the use of asbestos is now banned, there are about 3,000 deaths a year associated with asbestos-related diseases due to previous exposures. Of these deaths, 25% are workers in the building trade. This number is still rising and is expected to peak at about 10,000 per annum around 2010. Research shows that the workers mostly at risk are those involved in the maintenance of existing buildings (carpenters, electricians, cablers and plumbers), in asbestos removal, and in demolition. The families of those exposed at work can also be affected by the dust being brought back into their homes and a number of relatives have died through secondary exposure.

The risk associated with asbestos is determined by: the quantity inhaled over time; the size of the particles inhaled and whether they generate dust (in general long, thin, durable fibres are hazardous to health); and the durability in the lungs.

Silica Silica is a naturally occurring element present in many rocks and stones, particularly sandstone, quartz and slate. It is a highly toxic irritant when inhaled as a dust and can cause numerous chest and respiratory tract diseases. Silica has a workplace exposure limit (WEL) of 0.3 mg/m3, expressed as an 8-hour, time-weighted average (TWA). This means that exposure to respirable crystalline silica should be reduced so far as is reasonably practicable and, in any case, below the WEL.

Pneumoconiosis is the general term for an accumulation of dust in the lungs and the tissue reaction to its presence. There are two basic forms, as follows:

• Collagenous pneumoconiosis – which causes permanent alteration or destruction of the structure of the alveoli and permanent scarring of the lungs as a result of exposure to fibrogenic dust. Silicosis is a collagenous pneumoconiosis caused by inhalation of respirable particles of free silica.

• Non-collagenous pneumoconiosis – which results from exposure to non-fibrogenic dusts and involves no change to the structure of the alveoli tissue. The effect evoked by the dust is potentially reversible – i.e. the affected area may return to its original state if the dust is removed from the lung structure.

Mixed dust fibrosis results after the inhalation of dusts with variable proportions of silica and other materials.

In the early stages of infection, there may be only limited areas of collagenous pneumoconiosis which develop as the condition intensifies. Symptoms include:

• Breathlessness on exertion.

• Coughing with associated sputum.

• Chest pains.

In its later stages, impaired lung function puts a strain on the heart and death usually results as a combination of lung and heart failure.



Occupations at risk include quarrymen, masons, stone-cutting machine workers and stone dressers. The use of quartz in firing pottery has been replaced by alumina; silica grinding wheels have been superseded by carborundum.

Cement Dust and Wet Cement Cement is widely used in construction, e.g. mortar, plaster and concrete, and presents a hazard to health in a number of ways, mainly by skin contact, inhalation of dust, and manual handling (discussed in Element 4).

• Contact with wet cement can cause both dermatitis and burns.

• Cement is capable of causing dermatitis by irritancy and allergy.

− Irritant dermatitis is caused by the physical properties of cement that irritate the skin. Irritant dermatitis will usually clear up if treated properly. Exposure over a longer period will result in the individual being more susceptible to allergic dermatitis.

− Allergic dermatitis is caused by sensitisation to the hexavalent chromium (chromate) present in cement, and causes an allergic reaction. Hexavalent chromium is known to be the most common cause of allergic dermatitis in plasterers, concreters and bricklayers. Once someone has become sensitised to hexavalent chromium, any future exposure may trigger dermatitis. The risk of contact sensitisation to hexavalent chromium will be increased if cement is left on the skin and not washed off.

Both irritant and allergic dermatitis can affect a person at the same time.

• Wet cement can cause burns due to its alkalinity. Serious chemical burns to the eyes can also be caused following a splash of cement.

• High levels of dust can be produced when cement is handled, for example when emptying or disposing of bags. In the short term, exposure to high levels of cement dust irritates the nose and throat. Scabbling or concrete cutting can also produce high levels of dust which may contain silica, e.g. concrete and mortar contain crystalline silica (see earlier).

Cement, including mortars, grouts, tile adhesives, etc. containing chromium (VI) in greater than a 2 ppm concentration are prohibited for use and supply under COSHH (Amendment) Regulations 2004. The ban is to prevent allergic contact dermatitis when using wet cement and other products. A reducing agent can be used to lower such levels of chromium down to permitted levels. However, there still remains the potential for the treated cement to cause ill-health as it is an irritant and has high alkalinity.

Wood Dust Wood is classified in two broad categories – hardwood and softwood. Wood dust, and the resins, stains and wood preservatives contained in it are examples of substances which may be hazardous to health in the construction industry. The main activities causing such problems arise from sawing, routing, sanding, turning or operations with MDF (medium density fibreboard). Some protection may be required when working with hand tools in an open environment, but obviously harmful amounts of dust can be produced in enclosed or poorly ventilated areas when using hand tools, portable sanders and saws.

Certain types of wood have certain effects, which will depend on individual susceptibility and the dose received. The smaller the particle size and the greater the amount of dust produced, then the greater the risk of getting a health problem.

Health problems associated with exposure to wood dust are:



• Skin disorders.

• Obstruction in the nose, and rhinitis; asthma.

• A rare type of nasal cancer.

• Wheezing, coughing and breathlessness.

• Stomach disorders due to ingestion.

• Eyes – soreness, watering, conjunctivitis.

Wood has a workplace exposure limit (WEL) of 5 mg/m3 for both hardwood and softwood dusts, i.e. exposure to wood dust must be reduced so far as is reasonably practicable, and must not in any case exceed the WEL. Particle boards, e.g. chipboard and MDF, are composed largely of softwood and the dust produced from machining them should be treated as such.

Some common health problems are:

• Mahogany – asthma, dermatitis.

• Chestnut - asthma, dermatitis, rhinitis.

• Walnut - asthma, dermatitis, rhinitis, conjunctivitis.

• Sapele - dermatitis, allergic alveolitis.

• Ebony - irritation of nose and throat.

Other materials that may be found in woods which can be inhaled and have occupational exposure limits include 1.1.1-trichloroethane (in some adhesives), dichloromethane (in paint strippers and adhesives), isocyanates (in two-pack polyurethane paints and varnishes), certain glycol ethers which may be present in stains and varnishes, and arsenic pentoxide (in water-based wood preservatives). Some organic wood preservatives contain substances which have occupational exposure limits, e.g. lindane, white spirit, pentachlorophenol and tributyl-tin-oxide.

Exposure to substances which are known or suspected carcinogens, e.g. hardwood dust and inorganic arsenic compounds, can cause nasal cancer and skin cancer respectively.

Splinter wounds from some woods can be slow to heal and turn septic, e.g. greenheart and mansonia, while others like South African boxwood can give rise to whole body effects, e.g. headache, nausea, visual disturbance, anaemia, hepatitis.

Leptospira Weil’s disease is an infectious jaundice with symptoms of fever, jaundice, enlargement of the liver, haemorrhages and feverish relapses. The causative organism is a bacterium of the genus Leptospira.

Rats are the primary cause of the disease. Leptospira is found in the kidneys of rats and is excreted in urine and it is from this source that humans are infected. The primary routes of infection are through ingestion of contaminated water or food, and absorption where the skin is broken, although there is evidence that the bacterium can pass through intact skin. Persons at risk include canal workers, sewer workers, fish cleaners, tripe scrapers, pig workers, butchers, workers in abattoirs, rat catchers and agricultural workers.

Primary control is through systematic destruction of rats in infested areas. Control of the disease in sewer workers is difficult, but prophylactic immunisation seems to offer the best solution, together with a campaign of antibody testing. In addition, all ‘at risk’ workers should carry a card warning of the dangers, stressing personal cleanliness and hygiene,



explaining the need for protective clothing and alerting doctors to the possibility of the disease.

It is essential that people subject to potential risk are aware of the causes and symptoms, given instruction in suitable first-aid precautions (such as covering existing skin wounds, cleaning and disinfecting all fresh wounds), notify a GP if influenza-like symptoms occur and notify the relevant authorities if rat infestation is noticed in a work area.

Legionella Legionnaires’ disease is caused by the bacterium Legionella pneumophila, as is Pontiac fever, a shorter, more feverish illness, without the complications of pneumonia. Legionellosis is the generic term used to cover Legionnaires’ disease and Pontiac fever.

The bacterium thrives in certain wet conditions:

• Water temperatures in the range of 20-45°C – it does not survive above 60°C and the organism remains dormant in cool water.

• The presence of sediment, sludge, scale and/or organic material in the water – these can act as a source of nutrients, as can organisms such as algae, amoebae and other bacteria.

• Slime on the surface of water, where the incorporation of Legionella can protect the slime organisms from biocides.

Legionnaires’ disease is a type of pneumonia affecting the lungs and other organs of the body. Infection is caused by inhaling airborne droplets or particles containing viable Legionella, which are small enough to pass deep into the lungs and be deposited in the alveoli. The disease has an incubation period of three to six days and the initial symptoms include high fever, chills, headache and muscle pain. A dry cough soon develops and most patients suffer difficulty with breathing. In certain cases, this can lead to death, particularly among those with reduced resistance such as smokers, alcoholics and patients with cancer, chronic respiratory or kidney disease.

Exposure to Legionella can also lead to Pontiac fever, a milder condition with an incubation period between five hours and three days. Symptoms of Pontiac fever are similar to those of moderate to severe influenza, with headache, tiredness and fever.

Legionella is most commonly found in the water systems of buildings, with those potentially at risk being:

• Cooling towers.

• Evaporative condensers.

• Hot/cold water services in premises where the occupants are susceptible, such as health care premises.

• Humidifiers and air washers creating a spray of water droplets above 20°C.

• Spa baths and pools.

Employers can manage the risk of Legionella by:

• Identifying and assessing sources of risk, taking into account potential for drop formation, water temperature, exposure probability and adequacy of control.

• Implementing control measures to avoid conditions where Legionella can proliferate and to avoid creating sprays or aerosols – for example:

− Keeping the system clean and preventing a build-up of sediments and slimes.

− Avoiding the use of materials which provide nutrient for the organisms.

− Using appropriate water treatment chemicals.



− Avoiding stagnant or still water temperatures between 20°C and 45°C.

− Monitoring the water quality of ‘susceptible’ systems (those in premises which contain a high proportion of susceptible people) and situations where there is a large number of such people at risk.

Full information is to be found in an approved code of practice ‘Legionnaires’ disease’.

Hepatitis Hepatitis is a virus causing similar symptoms to Weil’s disease – fever, jaundice, enlargement of the liver, haemorrhages and feverish relapses. It is contracted primarily through injection, although ingestion of infected substances may also be a route of entry.

Persons exposed to the risk, who may include fire-fighters and ambulance workers in addition to those already mentioned, can be protected with injections of gammaglobulin. In all cases, protective disposable gloves should be worn and hands and arms washed regularly with disinfectant.

Hepatitis B in particular, is normally self-limiting with recovery in about six weeks. In about 5% of cases, chronic infectious hepatitis follows, leading to cirrhosis and possibly death.

Tetanus The organisms causing tetanus (lock-jaw) are widespread and can gain access to the body through cuts, wounds, splinters, vegetation, contamination soil, animal excretions, etc. Symptoms include stiffness in the muscles, a stiffening of the jaw until it is in a locked position, and breathing problems. There is a mortality rate of approximately 10%.

Immunisation helps to prevent the disease.

Construction workers are susceptible when working on new sites or where there has been any agricultural activity taking place. An immunisation programme should be encouraged for any such workers.




Revision Questions

1. State the forms of chemical agents which may be present in the workplace.

2. Identify the three general classifications of chemical hazards and the categories of danger associated with each.

3. What are the conditions which allow the Legionella bacterium to develop?

4. What is the difference between the effects of CO2 and CO?

5. What is pneumoconiosis?

6. What is the Approved Supply List?

(Suggested answers are at the end of Unit NCC1.)

?


RISKS ASSOCIATED WITH HAZARDOUS SUBSTANCES

Routes of Entry into the Body The process of entry into the body for a toxic or harmful agent is by absorption across the skin of the body (the outer skin) or across the lining (epithelium) of the lungs or gastrointestinal tract.

The route of entry is the way along which the agent is transported to, or arrives at, the site where absorption and entry occur. Note that absorption may take place anywhere along the route.

Substances can enter the body in many different ways.

Contact

Inhaled

Swallowed

Injected

absorbed

Routes of Entry

• Inhalation

Entry is through the nose or mouth and along the respiratory passages to the lungs. The lung is the most vulnerable part of the body, as it can readily absorb gases, fumes, soluble dusts, mists and vapours. This is the main means of entry of biological agents.

Note that there is a difference between inhalable substances and respirable substances. Inhalable substances are capable of entering the mouth, nose and upper reaches of the respiratory tract during breathing. Respirable substances are capable of deeper penetration to the lung itself. It is the size of the individual particle that determines whether a substance such as a dust is inhalable or respirable. Gases and vapours will be respirable because of their tiny particle size. Many fumes and mists will be respirable, but again it will depend upon how small they are.

Particles of a size which penetrate only as far as the thorax before becoming trapped, are described as thoracic dust.

• Ingestion

Entry is by the mouth and along the whole length of the gastrointestinal tract through the stomach and the intestines. Note that contamination may occur as a result of



swallowing the agent directly, from eating or drinking contaminated foods or from eating with contaminated fingers. All forms of chemicals may be ingested, and some biological agents may also find their way into the body by this route.

• Absorption

Entry is through the skin or via the eyes, either from direct contact with the agent or from contact with contaminated surfaces or clothing. It is mainly chemical liquids which enter the body in this way, although other forms of chemical may either sufficiently damage the skin to gain entry or find their way through the eyes.

• Aspiration

This describes the process whereby liquids or solids go direct into the lungs, other than by inhalation. Entry occurs while the epiglottis is open – for example, solid/liquid material originally ingested can run into the lungs when vomiting occurs, or liquids can be sucked into the lungs when using a pipette, if there is a sudden inrush of air at the bottom of the pipette.

• Injection

Entry is direct into the body by high pressure equipment or contaminated sharp objects piercing the skin. Chemical liquids, and sometimes gases and vapours, may enter the body in this way. There is also a risk of biological agents being injected – either on needles, etc. or by biting from an infected animal.

Superficial and Cellular Defence Mechanisms The body’s response against the invasion of substances likely to cause damage can be divided into superficial and cellular defence mechanisms.

Superficial The skin provides a useful barrier against many foreign organisms and chemicals. Sweat pores, hair follicles and cuts can allow entry and the skin itself may be permeable to some chemicals. The skin can only withstand limited physical damage due to its elasticity and toughness. Some forms of dermatitis arise as a result of this damage, leading to thickening and inflammation of the skin which is both painful and unsightly.

The respiratory tract forms a defence against inhalation. A series of reflexes activate coughing and sneezing mechanisms to expel the substance. Many substances and micro-organisms are trapped by nasal hairs and the mucus which lines the passages of the respiratory system. Fine hairs in the passages of the respiratory system form the ciliary escalator, which sweeps larger particles to the outside. In the deep lung areas, only small particles are able to enter the alveoli (where gas exchange with the red blood cells takes place), and cellular defence predominates there.

Ingestion of substances entering the mouth and gastrointestinal tract: saliva in the mouth and acid in the stomach provide useful defences to substances which are not excessively acid or alkaline. The wall of the gut also presents an effective barrier against many insoluble materials. Vomiting and diarrhoea reflex mechanisms act to remove substances or quantities which the body is not equipped to deal with without damage to itself.

The eyes and ears are potential entry routes for substances and micro-organisms. The eyes prevent entry of harmful material by way of the eyelids, eye lashes, conjunctiva (the thin specialised outer skin coating of the eyeball), and by bacteria-destroying tears.



The ears are protected by the outer shell or pinna, and the eardrum is a physical barrier at the entrance to the sensitive mechanical parts and the organ of hearing. Waxy secretions protect the eardrum and trap larger particles.

Cellular The cells of the body possess their own defence systems, for example:

• Prevention of excessive blood loss from the circulation through blood clotting and coagulation prevents excessive bleeding and slows or prevents the entry of germs into the blood system.

• Phagocytosis is the scavenging action of a defensive body cell (white blood cell) against an invading particle. A variety of actions can be used in this process, including chemical, ingestion, enzyme attach and absorption.

• Secretion of defensive substances is done by some specialised cells. Histamine release and heparin, which promotes availability of blood sugar, are examples.

• Inflammatory response can isolate infected areas, remove harmful substances by an increased blood flow to the area, and promote the repair of damaged tissue.

Assessing Health Risks Typically, the modes or routes of entry into the body can be used during the risk assessment process to identify the particular hazards associated with the use of certain materials, e.g. dust inhalation due to handling cement bags, or vapour inhalation while using adhesives.

Note that the route of entry into the body is critical in determining the appropriate control measures. Thus, where there is a risk of direct absorption, workers should be protected with appropriate clothing to prevent contact between the agent and the skin, or where the key entry route is through inhalation, respiratory protection will need to be provided.

Sources of Information As we noted previously, the CHIP Regulations and the European REACH Regulations collectively form the foundation of general chemicals regulation. We have seen how CHIP requires substances and preparations to be classified for their intrinsic hazards. Here we consider the requirements in respect of the provision of information to users by means of the labelling of chemicals and by safety data sheets.

Product Labels Under CHIP any substance or preparation which is classified as dangerous for supply must carry a label on its container giving the following information:

• The name of the substance (or, in the case of a preparation, the hazardous constituents).

• The indication(s) of danger and the corresponding symbols.

• The risk phrases (set out in full).

• The safety phrases (set out in full).

• The words “EC Label” (if the substance is on the Approved Supply List) and the EC number – for substances only (i.e. not required for preparations).

• Name, address and telephone number of the supplier.



The following table sets out the symbol letter, indications of danger and identifying symbol for each of the categories of danger used to classify dangerous chemicals. (Note that the letters are used only for shorthand reference, and are not to be used on labels themselves.)



Indications of Danger and Corresponding Symbols

Category of Danger Letter Indication of Danger Symbol

Physico-chemical Explosive E Explosive

Oxidising O Oxidising

Extremely flammable F+ Extremely flammable

Highly flammable F Highly flammable

Flammable - Flammable

Health Very toxic T+ Very toxic

Toxic T Toxic

Harmful Xn Harmful

Corrosive C Corrosive

Irritant Xi Irritant

Sensitising Xn Harmful

Xi Irritant

Carcinogenic

Categories 1 and 2 T Toxic

Category 3 Xn Harmful

Mutagenic



Toxic for reproduction



Environmental Dangerous for the environment

N Dangerous for the environment

The following example of a product label illustrates all the above points.



OLD BILL’S CITRIC THICK BLEACH contains Sodium Hypochlorite and Sodium Hydroxide

Keep out of reach of children. Irritating to eyes and skin. Avoid contact with skin and eyes. In case of contact with eyes, rinse immediately with plenty of water and seek medical advice. After contact with skin, wash immediately with plenty of water.

If swallowed, seek medical advice immediately and show the container or label.

Prepared by G and F Cleaners Ltd 431 Ocean Drive, Blackpool BL47 2FN, UK

Tel: 018050 999111

Sample Product Label

HSE Guidance Note EH40 Guidance Note EH40 is the prime source of information about airborne contaminants. It contains the lists of workplace exposure limits for use with the COSHH Regulations. The lists are reviewed annually, and include information on materials under review for inclusion or for a change of category, plus lists of materials classified as: “may cause cancer” or “may cause cancer by inhalation”.

Manufacturers' Safety Data Sheets Article 31 of REACH requires suppliers of dangerous substances and preparations to provide safety data sheets (this requirement was formerly within CHIP).

Safety data sheets are intended to provide users with sufficient information about the hazards of the chemicals for them to take appropriate steps to ensure health and safety in the workplace in relation to all aspects of their use, including their transport and disposal.

Safety data sheets must contain the following information:

• Identification of the substance or preparation (its commercial name, identical to that on the label) and supplier details – name, address and emergency contact phone numbers.

• Hazard identification – a summary of the most important features, including likely adverse human health effects and symptoms.

• Composition and information on ingredients – chemical names, classification code letters and risk phrases.

• First-aid measures – separated for the various risks, and specific, practical and easily understood.

• Fire-fighting measures – emphasising any special requirements.

• Accidental release measures – covering safety, environmental protection and clean-up.

• Handling and storage – recommendations for best practice, including any special storage conditions or incompatible materials.

• Exposure controls and personal protection – any specific recommendations, such as particular ventilation systems and PPE.



• Physical and chemical properties – physical, stability and solubility properties.

• Stability and reactivity – conditions and materials to avoid.

• Toxicological information – acute and chronic effects, routes of entry and symptoms.

• Ecological information – environmental fate of the chemical and its effects, which could include patterns of degradation and effects on aquatic, soil and terrestrial organisms, etc.

• Disposal considerations – advice on specific dangers and legislation.

• Transport information – special precautions.

• Regulatory information – such as labelling and any relevant national laws.

• Other information – such as list of relevant risk phrases, any restrictions on use (non-statutory supplier recommendations).

Safety data sheets must be supplied (paper or electronic) free of charge when the substance is first provided. They must be kept up-to-date and revised and reissued accordingly. In certain circumstances, relevant exposure scenarios must also by supplied as an appendix to the safety data sheet. As the name suggests, these are specific manufacturing/use scenarios (where exposure is likely) together with their respective control recommendations.

For a general introduction to REACH, download the free reference guide from the resource centre on the RRC website.

Limitations of Information in Assessing Risks to Health Product labels, safety data sheets and the occupational exposure limits (WELs) listed in GN EH40 provide detailed information about the hazards and risks associated with a wide variety of hazardous substances. They ensure that users are well briefed on the properties of materials used in the workplace and such essential requirements as exposure limits, toxicological effects, first-aid and safety precautions, e.g. any personal protective equipment necessary. This is an essential first step towards putting in place effective control measures necessary to prevent harm.

However, it is important to remember that this information is not all that is required to establish effective controls. The basis of determining control measures is the risk assessment. Whilst information from the sources discussed here feeds into a risk assessment, it is only one part of it. It needs to be complemented by further information about the nature of the work and working practices before any evaluation is made about the risks to health posed by substances used at work.

Remember that product labels, safety data sheets and WELs are general statements. They do not allow for the localised conditions in which the substances are to be used.

Basic Surveys for Health Risks Occupational exposure limits are the basis for ensuring that exposure to airborne substances hazardous to health is reduced to the lowest possible level. In order to ensure that these are being adhered to, there must be a programme of monitoring to measure levels of contamination.

Monitoring consists of sampling and testing the air quality by a variety of means, as discussed below. This may be in respect of the general atmosphere in the workplace or in respect of the immediate environment around individual employees who may be at particular risk. In addition, monitoring will also be carried out to test the effectiveness of specific control measures, such as ventilation systems.



Monitoring exposure levels and testing as part of the maintenance of control systems are specifically required as part of the following Regulations:

• Control of Asbestos Regulations 2006.

• Control of Lead at Work Regulations 2002.

• Control of Substances Hazardous to Health Regulations 2002.

It is a specific requirement of the COSHH Regulations that engineering controls provided to reduce exposure to substances hazardous to health, such as local exhaust ventilation systems, must be thoroughly examined and tested at least once in every 14 months. For certain processes – such as the blasting of metal castings, dry grinding of certain metals, production of non-ferrous metal castings and jute cloth manufacture which all give rise to particularly hazardous dust or fumes – a more frequent examination interval is specified.

Sampling Techniques The first task in monitoring air quality is to collect the sample of air so that it may be analysed. There are a number of considerations here, with the decision of the approach to be used depending on the risk level of the contaminant being assessed.

• Location of the Sample

Samples may be taken in the general working atmosphere, in the operator’s breathing zone, or at a position close to the contaminant generation.

• Method of Analysis

The procedure may involve sampling and analysis in the same instrument, or taking the sample collected and analysing it using different equipment, perhaps in a laboratory away from the point of collection.

• Duration of the Sampling

There are three approaches to this:

− A spot or grab sample – which is a single sample collected instantaneously at a particular location or in a limited area and is representative only of that location or area at that point in time. Such samples may be analysed on the spot by the same instrument or be taken away for subsequent laboratory analysis. To obtain time-averaged levels, a series of spot samples may be taken over the period in question, but this is not necessarily accurate.

− A better method of obtaining a time-weighted average is by collecting a sample over a period and then analysing it. This is the usual technique for personal monitoring.

− A continuous monitored sample – where a sample is collected continuously over a period of time. Here the sample will be analysed during the monitoring, either by the sampling instrument itself or by direct connection to another instrument which carries out the analysis continuously. Such systems may be linked to an alarm system so that, if a set level is reached, the alarm is activated.

• Frequency of the Sampling

The frequency with which spot samples are collected will depend on the type of contaminant and/or the results of the last sample. Thus, for example, if an initial sample is borderline to an OEL on entering a confined space for inspection purposes, further samples may be taken very frequently until a satisfactory reading is obtained.



On the other hand, if the initial sample showed that the atmosphere was safe, no further readings would be necessary for a considerable period.

To obtain time-averaged levels, either a series of spot samples may be taken over the period in question or spot readings may be taken from a continuous sample.

Both the frequency of sampling and the method of analysis are also influenced by the main purpose of the monitoring. There are basically two general purposes:

• To indicate the presence of, and identify, contaminants – which requires a qualitative analysis of the sample to determine its exact constituents.

• To determine exact concentrations of a particular contaminant – which requires a quantitative analysis of the sample in respect of a known agent. This type of analysis is easier to achieve within the same instrument as is used to collect the sample since it is only testing for the presence of one particular agent. This type of analysis is used to assess compliance with OELs and to activate alarm systems.

Finally, here, we need to distinguish between the two basic methods of sampling, based on the way in which the sample is collected.

• Diffusion or passive sampling – here, the contaminant passes over the sampling system in natural air currents and diffuses into a chamber containing an absorbent material which can be removed for later analysis. These systems are used for continuous sampling over a period of time, and can only produce cumulative results for that period as a whole.

• Mechanical or active sampling – these systems use a pump to provide airflow through the sampling device or analysing instrument. They can be used for both spot and continuous sampling, and in the case of the latter, individual readings at particular points in time over the period may be extracted, depending on the type of instrument used.

Stain Tube Detectors These detectors are simple and easy to use and are perhaps the most convenient method of analysing gaseous contamination of the workplace air.

The principle of operation is very simple – a known volume of air is drawn over a chemical reagent contained in a glass tube. The contaminant reacts with the reagent and a coloured product, a stain, is produced. To illustrate the principle, consider the breathalyser – the ‘contaminated air’ is blown into the tube and, if the concentration of alcohol in the air is high enough, the reagent in the tube changes colour.

Stain tube detectors used in the workplace give a direct reading of the concentration of the contaminant being measured. The instrument comprises a glass tube containing the chemical reagent fitted to a hand-operated bellows pump or a manual or motorised piston-type pump. Many types of tube are available, with different chemicals that react to different gases. To operate, the appropriate detector tube is placed in the pump, and the bellows pump is squeezed or the handle of the piston-type pump is pulled back for a specified number of strokes. This draws air through the detector tube, the chemical in the tube changes colour, and the concentration of the gas can be read from the scale marked on the tube.




The following diagram illustrates the principle:

Scale Detector Tube

Note the colouration on the used tube indicating a concentration of 50 ppm carbon monoxide, the number of strokes (n = 10) necessary to pass the required amount of air through the tube, and the arrow showing the direction of air flow.

The instrument can be used for spot or continuous sampling, depending on the number of strokes or time for which the pump is operated.

There are a number of different types of stain detector tube, including the following:

• Draeger multigas detector – the basic type of instrument comprising a bellows pump and the Draeger tube, selected to suit the particular measurement to be carried out.

• Automatic multigas detector – this has an electrically-operated bellows-pump model which can be set to switch off when the selected number of strokes for the particular tube is complete. It is useful where an operator has to be free during testing and where the measurements require a high number of strokes.

• Polytest tubes – these are designed to make qualitative measurements to determine only the presence of potentially harmful substances. Varying colour and stain length sometimes give an indication of the possible contaminant.

• Toxicator gas detector – this system draws air across a chemically impregnated tape which changes colour in reaction to the level of contaminant. The key difference here is that the tape is automatically moved on to expose a clean section for the next measurement.

Stain detector tubes can be quite flexible in the way in which they are used. Reading off the measurement may be manually by an operator or it may be automatic by means of an electronic optical sensor. Also an extension hose can be placed between the pump and the tube so that the air inside a structure can be measured without the operator having to enter the structure.

There are certain limitations on the use and reliability of stain tube detectors, including:

• The rate of flow of air is important, so the assembly of the instrument must be performed correctly – the joint between the bellows/pump and the tube must be sealed and the ends of the tube should be removed properly.

• The accuracy of the sampled volume is critical, so the bellows/pump action must be fully operated for every stroke. The number of strokes must be recorded accurately, hence the need for an effective counter.

5 10

30

50

70

110

90

130

150

CO

n = 10

5 10

30

50

70

110

90

130

150

CO

n = 10

unused

used contaminant stain


• There may be the possibility of cross-sensitivity of tube reagents to other substances than the one being analysed. This will be indicated on the data sheet accompanying the particular stain tube.

• There may be problems caused by variations in temperature and pressure. Stain tubes are designed to operate at about 20°C and one atmosphere pressure. Variation in atmospheric pressure will probably be within the limits of accuracy of the system, although changes in altitude could cause problems. Normal variations in temperature are more problematic – a change of 10°C can cause a reaction rate to be doubled or halved, and with ambient temperature ranging between 0°C and 30°C, the potential for error is considerable.

• Because of the complexity of the indicating reagent, tubes have a shelf life, so care must be taken to turn over stock and use only currently operative tubes.

• Reagent complexity also causes a variation between each tube, so judgments cannot be made on one spot sample.

• Hand-operated stain tube systems are capable of only a single ‘point-in-time’ spot sample.

Passive Samplers Passive devices employ absorbent material to sample concentrations of airborne pollutants without using a pump to draw air through the collector. The absorbent material is contained in a holder designed to allow the gases to diffuse and/or permeate to the absorbent surface. At the end of the sampling period, the holder is returned to the laboratory, where the absorbent material is removed and the amount of gas or vapour collected can be analysed.

There are two main types of design:

• The dish-type sampler has a flat, permeable membrane supported over a shallow layer of sorbent (see diagram (a) below).

• The tube-type sampler has a smaller permeable membrane supported over a deep metal tube filled with sorbent (see diagram (b) below).

These types of sampler are very versatile. They can be left open for varying periods of time, so can take both spot samples (although not instantaneous ones as with active samplers) and continuous samples. They can be made to virtually any size and, free of any pump, tubing or a need for an operator, can be positioned anywhere there is an appropriate fixing point. The smaller dish-type samplers can be worn like a lapel badge to provide a very personal monitoring device, giving a quite precise indication of the actual exposure the wearer is subject to. (It is also easy to ensure that they are used, as it can be seen immediately whether the person is wearing it.)




Passive (Diffusion) Samplers

There are limitations on the effectiveness of passive samplers for monitoring purposes, including the following:

• They do not provide any immediate indication of the contamination concentration – the results have to come back after analysis and, therefore, relate to a past period.

• They only measure accumulated concentrations over the period for which they are in use – they cannot be easily used to calculate time-weighted averages.

• They only sample contamination at the fixed point at which they are located or, in the case of badges, where the wearer is – they cannot be easily used to take spot samples in various parts of the workplace.

• They are easy to take off, thereby rendering them ineffective.

• The size of the sample is imperative. If the samplers are only used intermittently or only a small sample is used, the results may be misleading.

Oxygen Meters Direct reading instruments can be used to measure a variety of gases in the working environment. Stain detector tubes are used to qualitatively identify the presence of gases and to measure a variety of gases either semi-quantitatively or quantitatively. Direct reading instruments are more appropriate for commonly occurring gases such as oxygen, nitrogen and carbon dioxide. The performance of direct reading instruments is far more reliable and reproducible in terms of accuracy and precision. They should therefore be the method of choice under these circumstances.

Direct reading instruments are available to monitor and warn of concentrations of the toxic gases carbon dioxide, carbon monoxide or hydrogen sulphide in the atmosphere as well as the essential gas, oxygen, in naturally occurring respirable air.

Instruments designed to monitor and warn of concentrations of oxygen in the atmosphere indicate concentration on a simple dial or digital readout. To determine the concentration of oxygen in the environment, an air sample diffuses into the equipment sensor through a special membrane, where the resultant electrochemical process produces electric current directly proportional to the oxygen concentration.

Permeable membrane Retaining ring

Sorbent

Metal tube

Sorbent

Permeable membrane

(a) Dish-Type Sampler

(b) Tube Sampler


The instrument can be pre-set to a given oxygen concentration which activates an audible or visual alarm system. They are used as both personal monitors and to measure room concentrations of oxygen.

The normal percentage of oxygen in air is 21%, most of the remainder (78%) being nitrogen.

Smoke Tubes Smoke tubes are used to assess the strength and direction of air flow. They release a cloud of smoke which is then carried away by the air currents in the local environment and the movements observed.

Such smoke tests are ideal for checking the effectiveness of ventilation or air conditioning systems and chimneys, or to detect leaks in industrial equipment. They are also used to assess relative air pressures which are used to force air flow in a particular direction through certain types of local ventilation system (such as fume cupboards – see later). In addition, they provide general information about air movements in a work area which can be very useful when assessing the best locations for sampling devices.

Different types of smoke tube are available to produce varying consistencies and colours of smoke, enabling the test to be tailored to the conditions in the workplace. They can also produce small single clouds as well as continuous smoke.

The major drawback of this method of testing is that it does not take account of the particle sizes of contaminants actually encountered in individual workplaces. The smoke may be more easily captured by a ventilation system than the contaminant particles. As a consequence, a false sense of security can be engendered. Open doors and windows can affect the direction and rate of airflow.

Dust Monitoring Equipment Dust Lamps (Tyndall Beam) Airborne dust in the workplace which is not visible to the naked eye can be monitored by means of a rudimentary device known as the Tyndall lamp.

LIGHT BEAM

OBSERVER SCREEN

ILLUMINATED DUST CLOUD

POWERFUL LAMP

Tyndall Beam Apparatus

A strong beam of light emitted from the lamp is shone through the area where a cloud of finely divided dust is suspected of being. Non-visible dust clouds will deflect the light beam by between 5° to 15°. The eye of the observer is shielded from the light beam by means



of a barrier such as a small hand-held card. Dust clouds are consequently made visible. The light scattering is visualised by the observer, and the dust cloud is detected.

The method is used to determine how exhaust ventilation systems are working. Tyndall lamps do not provide numerical data but are useful for screening methods.

Direct-Reading Dust Analysers A variety of hand-held, portable monitors are available which will detect and measure both airborne dusts and aerosols. Some work by similar principles to the Tyndall lamp. Such photometers which measure light deviation caused by dust clouds are known as nephelometers.

They can be used statically in the workplace or worn personally to detect personal exposure.

Indirect-Reading Filtration Equipment Such devices can be worn personally by the worker or mounted statically in the workplace. Dust is collected onto a pre-weighed filter and then eluted in the laboratory for gravimetric analysis.

Multi-Orifice Total Inhalable Sampler

(Source: MDHS 14/3 General Methods for Sampling and Gravimetric Analysis of Respirable and Inhalable Dust)

(Reproduced under the terms of the Click-Use Licence)



WORKPLACE EXPOSURE LIMITS Workplace exposure limits (WELs) provide the basis for controlling airborne contamination of the working environment. They define standards for air quality in terms of the amount of a particular substance which is acceptable in the atmosphere. Monitoring of the air quality can then take place to ensure that the limits are not being exceeded.

The WELs for substances hazardous to health are laid down in HSE Guidance Note EH40.

Measuring Exposure in Units The two main units used for measuring airborne concentrations are:

• Parts per million (ppm).

• Milligrams per cubic metre of air (mg/m3, or mg m-3).

The gaseous state (vapours and gases) is measured in ppm and refers to the number of parts of vapour or gas of a substance in a million parts of air by volume. Particulate matter in dusts, fumes, etc. is measured in mg/m3, which refers to the milligrams of the substance per cubic metre of air.

One further unit of measurement is used in relation to fibres (such as asbestos); concentrations of fibres are expressed in fibres per millilitre of air (fibres ml

-1 ).

Workplace Exposure Limits WELs are occupational exposure limits (OELs) set under Regulation 7 of COSHH 2002 (as amended).

A WEL is the concentration of a hazardous substance in air, averaged over a specified period of time, which must not be exceeded.

For the average over a reference period – referred to as the time-weighted average (TWA), two time periods are used – the long-term exposure limit (LTEL) over eight hours, and the short-term exposure limit (STEL) over 15 minutes.

WELs are listed in the HSE publication “EH40 2005: Workplace Exposure Limit” which is updated by annual supplements. EH40 also provides detailed guidance on the use of WELs.

Regulation 7 of COSHH clearly states that control of exposure to hazardous substances will only be treated as adequate if the appropriate WEL is not exceeded. Thus it can be viewed as a maximum or ceiling which must not be exceeded on a time-weighted average basis.

It is also worth noting that Regulation 7 also clearly states that control of exposure to hazardous substances will only be treated as adequate if the “principles of good practice” for control have been applied.

The two tests for adequacy of control apply in the case of exposure of employees to any substance hazardous to health. However, in certain situations a stricter level of control is required by Regulation 7 of COSHH. Where the hazardous substance is either carcinogenic/mutagenic (i.e. carries the risk phrase R45, R46, R49 or is listed in Schedule 1 of COSHH) or is capable of causing occupational asthma (i.e. carries the risk phrases R42, R42/43 or is listed in Section C of the HSE publication “Asthmagen? Critical Assessments of the Evidence for Agents Implicated in Occupational Asthma”) then control will only be deemed adequate if exposure is reduced to as low a level as is reasonably practicable.

So for most substances assigned a WEL employers can achieve adequate control by applying the “principles of good practice” and by ensuring that the WEL is not exceeded.



For carcinogens, mutagens and sensitising agents capable of causing occupational asthma, employers must ensure that the control measures in place reduce employee exposure as far below the WEL as is reasonably practicable. Thus, for these latter substances a higher degree of control is required by law and can be enforced. For these substances it is not enough just to be below the WEL. Workplace exposure must be below the WEL and further reduced below the WEL to the greatest extent reasonably practicable.

Long-Term and Short-Term Limits The effects due to exposure to hazardous substances depend on the nature of the substance and the length of the exposure – some effects require prolonged or accumulated exposure whilst other effects become apparent very quickly. WELs are, therefore, usually stated as:

• Long-Term Exposure Limit – the level of airborne contaminant allowable over an 8-hour period, used for substances producing chronic effects.

• Short-Term Exposure Limit – the level of airborne contaminant allowable over a 15-minute period, used for substances producing acute effects.

The concentration levels are expressed as time-weighted averages (TWA). This means that measurements are taken over the period in question and the airborne concentrations are then averaged out.

The concept of a TWA allows concentration levels to exceed the limit, provided that there are equivalent exposures below it to compensate. There are no stated levels of the extent to which the limits may be exceeded, but the general rule is that exposures of one-and-a-half times the limit require urgent improvement in control strategies.

Limitations of Exposure Limits Whilst WELs provide a general basis on which to assess what may be a safe level of concentration of airborne contamination, it should not be assumed that, provided the level does not exceed the stated limit, it is necessarily safe in all circumstances. WELs do not pretend to provide complete protection and there are a number of limitations. WELs are designed only to control the absorption into the body of harmful substances following inhalation. They are not concerned with absorption following ingestion or through contact with the skin or the eyes. Where substances can be absorbed following skin contact, a warning is given by noting this characteristic by the abbreviation “Sk” alongside the exposure limit.

Other limitations include:

• They take no account of human sensitivity or susceptibility. This is particularly important in the case of substances which produce an allergic response – once a person has become sensitised, the exposure limit designed to suit the average person has no further validity.

• They do not take account of the synergistic effects of mixtures of substances – for example, the use of multiple substances in pest control or the presence of other harmful substances in the atmosphere (such as radiation).

• They do not provide a sharp dividing line between ‘safe’ and ‘dangerous’ conditions, although that is often assumed. If this was true, though, the concept of time-weighted averages could not be used, since levels above the limit would not be permitted.

• As long-term exposure limits are based on an 8- hour TWA, they cannot be applied directly to working periods which exceed this – for example, long shifts or overtime.



• They may become invalid if the normal environmental conditions are changed – for example, changes in temperature, humidity or pressure may increase the harmful potential of a substance.

Principle of Reducing Exposure Levels The operation of WELs is based on the concept of controlling risk by reducing the workplace exposure to the contaminant. Thus, the COSHH Regulations require that exposure to harmful substances should be reduced to the lowest level reasonably practicable.

Ideally, a ‘no exposure’ limit is the best possible strategy for controlling risk. Although this has been adopted for certain chemicals, especially where carcinogens are concerned, this is impractical in most situations when we take into account the requirements of working processes. Thus, limitation of the risk becomes the next best strategy.

In practice, reducing exposure may mean more than simple compliance with the stated WEL. Under the COSHH Regulations requirement, if it is reasonably practicable to get contamination levels even lower, then that standard should be achieved.



ACUTE AND CHRONIC HEALTH EFFECTS

Distinction Between Acute and Chronic Health Effects Acute health effects arise where the quantity of a toxic or harmful substance absorbed into the body produces harmful effects very quickly – i.e. within seconds, minutes or hours.

In an occupational setting, acute toxicity does not often occur because the conditions required to produce it are either too complicated, or the results would be so serious that stringent safety measures are observed, thus preventing its occurrence. Gassing accidents producing toxic conditions are an exception.

The term ’chronic toxicity’ describes a condition where the harmful effects of a substance absorbed into the body take a very long time to appear – months or perhaps years. The conditions produced by the toxin usually result from absorption of small quantities over a period of time. In terms of occupational safety, chronic toxicity, or at least its prevention, presents the most difficult control problems.

This is particularly true if materials have little-known or poorly-documented toxicity levels, or if hygiene control strategies are breaking down. The following points illustrate how insidious are the effects of chronic toxicity and give an indication of the difficulties of achieving effective control:

• The effects occur over a long period, so the hazard is not recognised.

• The level of contamination required to produce chronic effects is often tolerated by people because they do not experience acute symptoms.

• Symptoms occur slowly, so they are not recognised until an advanced condition of harm has developed.

• When symptoms are recognised, the harm may be too advanced for full recovery – sometimes no recovery is possible.

• Symptoms are often confused with ‘normal’ ill-health or with ‘getting older’.

• Symptoms are not always easily identifiable in groups of people with the same exposure, owing to the effect of differing ‘personal’ metabolisms.

It is important to note that for both acute and chronic toxicity, time is involved in relation to their definition, but that the level of toxic action is not defined. Acute toxic action does not necessarily mean death. Intoxication from drinking alcohol is an acute toxic condition, but only in rare cases is it the direct cause of death. Cirrhosis of the liver related to intoxication by alcohol is a chronic toxicity condition from which death can occur.

Some toxic substances, such as cyanide and paraquat, are generally considered to be acute toxins only.




Revision Questions

7. Identify the routes of entry of chemical and biological agents into the body.

8. What is the difference between an inhalable substance and a respirable substance?

9. What is Guidance Note EH40?

10. What is a workplace exposure limit (WEL)?

11. What do you understand by the term ‘time-weighted average’ in relation to a WEL?

12. Give three examples of the limitations of WELs.

13. What information must be provided on the label of a preparation which has been classified as dangerous for supply?

14. What is the purpose of safety data sheets?

15. What do the following symbols indicate?

(a)

(b)

(c)

16. What is the difference between passive and active sampling devices?

17. Give three examples of limitations in the use of stain tube detectors.

18. What are smoke tubes used for?

19. Distinguish briefly between acute and chronic ill-health effects.


?


APPROPRIATE CONTROL MEASURES The precautions taken to control risks arising from chemical and biological hazards should be established following an appropriate risk assessment. This will involve both the analysis of the nature of the risks present in the workplace and a critical evaluation of existing control measures. From this, a decision must be made as to what, if any, improvements or additional measures are necessary to reduce the level of risk further.

Duty to Prevent Exposure Both the Management of Health and Safety at Work Regulations and the COSHH Regulations require that measures conform to the general hierarchy of control:

• Eliminate the hazard.

• Use physical or engineering controls, which reduce the risk at source and provide protection generally rather than individually.

• Control the person by job design, management, or (as a last resort) personal protective equipment.

Prevent Exposure The COSHH Regulations require the employer to prevent exposure to substances hazardous to health if it is reasonably practicable to do so. The employer might:

• Change the process or activity so that the hazardous substance is not needed or generated.

• Replace the substance with a safer alternative.

• Use the substance in a safer form, e.g. pellets instead of powder.

The HSE guidance booklet, Seven Steps to Successful Substitution of Hazardous Substances, advises on how to replace hazardous substances with safer alternatives.

Adequately Control Exposure If prevention is not reasonably practicable, the employer must adequately control exposure. He should consider and put in place measures appropriate to the activity and consistent with the risk assessment, including, in order of priority, one or more of the following:

• Use appropriate work processes, systems and engineering controls, and provide suitable work equipment and materials, e.g. use processes which minimise the amount of material used or produced, or equipment which totally encloses the process.

• Control exposure at source (e.g. LEV), and reduce the number of employees exposed to a minimum, the level and duration of their exposure, and the quantity of hazardous substances used or produced in the workplace.

• Provide personal protective equipment (e.g. face masks, respirators, protective clothing), but only as a last resort and never as a replacement for other control measures which are required.

Meaning of “Adequate Control” Under COSHH, adequate control of exposure to a substance hazardous to health means:

• Applying the eight principles of good practice set out in Schedule 2A of COSHH (see below);



• Not exceeding the WEL for the substance (if there is one); and

• If the substance causes cancer, heritable genetic damage or asthma, reducing exposure to as low as is reasonably practicable.

Ensuring WELs are not Exceeded The HSC has established WELs for a number of substances hazardous to health. These are intended to prevent excessive exposure to the substance by containing exposure to below a set limit. Correctly applying the principles of good practice will mean exposures are controlled below the WEL.

The eight principles of good practice are outlined below:

• Principle 1

Design and operate processes and activities to minimise emission, release and spread of substances hazardous to health.

• Principle 2

Take into account all relevant routes of exposure – inhalation, skin and ingestion – when developing control measures.

• Principle 3

Control exposure by measures that are proportional to the health risk.

• Principle 4

Choose the most effective and reliable control options that minimise the escape and spread of substances hazardous to health.

• Principle 5

Where adequate control of exposure cannot be achieved by other means, provide, in combination with other control measures, suitable personal protective equipment.

• Principle 6

Check and review regularly all elements of control measures for their continuing effectiveness.

• Principle 7

Inform and train all employees on the hazards and risks from substances with which they work, and the use of control measures developed to minimise the risks.

• Principle 8

Ensure that the introduction of measures to control exposure does not increase the overall risk to health and safety.



Methods of Control Elimination or Substitution of Hazardous Substances Elimination

The first priority for control of any significant risk to health is to try to eliminate completely the agent responsible in the first place. Both the COSHH Regulations and the Manual Handling Regulations specifically require the employer to avoid exposing employees to the risk first, before any other control measures are considered.

For each of the agents we have examined, the option usually exists to eliminate the hazard at source by replacement with materials which do the same job, but present no risk to health. Improvements in technology often present the opportunity to replace older hazardous processes or activities with those involving no risk to health – for example, the use of new, water-based materials such as paints or adhesives can eliminate completely the risk to health of exposure to solvents.

Elimination requires a careful examination of the work activity and process, and demands a good understanding of the properties and behaviour of alternative substances and materials. It may also be the most costly method of risk control, since it may involve a radical change in the way that the work is carried out. However, the elimination of hazards is the overriding goal of the health and safety programme and the opportunities available should be re-examined every time an assessment is reviewed.

Substitution

Although elimination of risk is the ideal, it is often not practicable. The next option then becomes reducing the risk by replacing the hazard with a different one with less potential for harm – for example:

• Using the same material, but in a different physical form, such as using a water-based paint instead of one containing a volatile organic solvent.

• Using a similar, but different substance altogether, such as one with a lower volatility and/or WEL.

Since the risk is not completely eliminated but only reduced, it is essential to ensure that the potentially harmful properties of any proposed replacement are fully taken into account to ensure substitution does not introduce different, but equally unacceptable risks.

Process Changes In some circumstances, an analysis of the process itself may identify specific activities which produce harmful substances or agents. In these cases changing the work method may minimise or suppress the generation of the agents of concern – for example:

• Brush painting rather than spraying will considerably reduce the level of airborne contaminant.

• Vacuuming, rather than sweeping up (which pushes dust into the air), reduces dust levels.

• Damping of a substance during mixing or when clearing up also reduces dust levels.

In general, therefore, the aim is to identify the particular element of the process or work activity which is responsible for the harmful agent and try to replace this element with one with less potential for harm. The opportunities for this may, though, be constrained by practicability from a production point of view.



Reduced Time Exposure The ill-health effects arising from hazardous substances and agents in the workplace are often related to the length of time of exposure as well as the severity (the concentration) of the contaminant. As a consequence, reduction of exposure can be used as a means of minimising possible ill-health effects.

As a general principle, when a hazard exists from a substance or a physical agent, the cumulative dose should be reduced to as low a level as possible by organising the work pattern to provide periods of nil exposure. There are two methods of achieving this, based on establishing safe exposure time limits:

• Providing for regular breaks away from contact with the hazardous substance.

• Job rotation – where the exposure of any particular individual is reduced by sharing the dose with other workers, such as having a number of workers performing a task in rotation, with strict control over length of time of exposure in order to ensure that dose limits are not exceeded.

Enclosure and Segregation The control measures considered previously are all based on either preventing the risk or reducing it in some way to an insignificant level. If this approach is not possible then we have to consider physical controls which enclose the hazard and segregate people from the process involving it.

Total enclosure or containment of the hazard is the best form of such control since no-one can then be exposed to it – for example, total enclosure of a process which generates dust or fumes will prevent the escape of airborne contaminants which could be inhaled by operators in the vicinity. When an area has been totally isolated, it may still be necessary to access equipment or material within that area and accordingly the use of robotically-controlled, remote handling systems may be incorporated, allowing access without disturbing the integrity of the enclosure.

Where isolation of the source is difficult, it may be more practical to enclose the workers to ensure that they remain segregated from the hazard.

There will always be situations where it is not possible to totally enclose the process or the workers at all times – for example, when cleaning or maintenance work has to be carried out, or access is necessary to introduce raw materials or remove the product. Special measures will then be necessary to prevent any escape of the substance during periods when the integrity of the enclosure will be broken – for example, through the use of ventilation systems to carry away any airborne contaminants.

Local Exhaust Ventilation Local exhaust ventilation (LEV) is the standard control measure for dealing with dusts, vapours and fumes which are generated from a point source. The harmful contaminant is extracted at the point of generation using engineered systems to ensure that the direction of the ventilation flow is away from the breathing zone of any operators.

Examples of LEVs include:

• Glove boxes – total enclosures, often used in laboratories, which are accessed through flexible gloves and kept under negative pressure to prevent any release of contaminant.

• Fume cupboards – partial enclosures, again often used in laboratories, which are accessed through a vertical sliding sash, with the enclosure again being kept under



negative pressure so that the air flow is through the sash into the hood to prevent any release of contaminant.

• Captor hoods – movable ventilators which can be positioned as near as possible to the hazard and capture contaminants by a negative air flow into the hood before they reach the operator, such as are used to extract woodworking dust.

• Receptor hoods – large structures designed to capture contaminants which have been directed naturally into the hood by thermal draughts, directional movement, or by local generation. An example of a receptor hood is a chimney in an incinerator.

To be effective, the LEV must be properly designed and located close to the source of contamination so that the system can extract all, or at least sufficient of the contaminant to prevent exposure above the WEL. Capture and extraction may be through engineered natural air flows, such as pressurised systems, or by the use of fans or pumps to suck the air away. Some systems are very noisy and this in itself may represent a hazard.

The contaminant must be carried away by secure ducting to an exhaust outlet. There will usually be some form of filter fitted between the capture hood and the outlet to remove as much of the contaminant as possible before venting.

The positioning of the outlet itself is important. The exhausted air must exit the system to a safe place. This will usually be into the atmosphere, and care must be taken to ensure that this does not create an atmospheric pollution problem – factors such as chimney height and prevailing wind direction and speed must be considered to ensure adequate dispersal. The efficiency of the exhaust outlet must not be impaired by variations in wind direction or by weather cowls (these should be sited well away from the end of the duct). Exhausted air must also be directed away from any air inlets, otherwise a cyclic pollution system is produced.

Factors that Reduce Effectiveness

• If extra hoods and ducting need to be added on to the original design, care must be taken to keep the flow of air as straight as possible.

• Filters may become blocked.

• Changes in air currents will affect the operation, such as opened doors and windows.

• The contaminants may be made up of different particle sizes and larger particles will require more force to capture them.

Inspection and Monitoring

The ultimate proof of satisfactory performance of an exhaust ventilation system is that it maintains an acceptable work environment where atmospheric concentrations of airborne contaminants are kept below occupational exposure limits. Consequently, periodic air monitoring or even continuous monitoring needs to confirm that effective protection is being maintained and to identify signs of deterioration so that remedial action can be taken before harm occurs.

Any new system should be carefully examined and tested as part of the commissioning to ensure it is able to meet the design specification.

In use, there are a range of engineering tests and inspections:

• Regular visual inspections, either as part of daily operations or as a more formal procedure perhaps involving specific checks, are often a first indication that there is a problem. A typical example might be where a local exhaust ventilation system is in place to remove sawdust generated by a circular saw. An excessive build-up of sawdust around the saw might indicate a problem with the system.



• All hoods should be examined in detail to ensure they effectively capture or contain the contaminant. This may be done by using smoke generation to follow the air flows around a hood or by taking air-flow measurements.

• Manometers (pressure gauges) or U-tubes can be used to measure static pressures at hoods or enclosures. They can also be used to measure pressure drops across filters or air-cleaning plant. The measurements will confirm the suitability of air-flow distribution and agreement with the design specification.

• In dust collection systems, a check should be made on pipe velocity to ensure that ducts will remain free of dust settlement.

• Air-cleaning plant and fans should be checked for continued compliance with the design specification.

Local exhaust ventilation provided as a control measure for COSHH substances should be thoroughly examined by a competent person every 14 months.

Dilution Ventilation – Uses and Limitations Dilution ventilation operates by simply diluting the contaminant concentration in the general atmosphere to an acceptable level. This is achieved by efficiently changing the air in the workplace over a given period of time – for example, a number of complete changes every hour. The workplace air will be extracted by the use of fans set in the walls or roof, with fresh air being pumped in.

The system is intended to remove gaseous contaminants (sometimes fumes) and keep the overall concentration of any contaminant to below the OEL and/or the concentration of a flammable substance to below its lower explosive limit. Where both a harmful and flammable substance is encountered, such as propanone (acetone), then control of the first objective will invariably control the second.

Dilution ventilation has fairly limited use as an effective control strategy in occupational hygiene. It can, however, be used with reasonable success provided the contaminants conform, where applicable, to the following:

• The OEL of the harmful substance is high.

• The vapour pressure of a liquid is low – i.e. it has a low evaporation rate.

• The rate of formation of the gaseous product is slow.

• Operators are not in close contact with the contamination generation point.

• Any hazardous substance is carried swiftly away from the operator.

When contaminants are to be removed from a workplace using dilution ventilation, two important criteria have to be considered.

• The Rate of Contaminant Generation

This conditions the number of air changes per hour required. Relevant factors in respect of the generation of contaminated vapour from liquids include:

− The vapour pressure and potential to evaporate at the operating temperature of the system.

− The surface area of the liquid in contact with the workplace air, including the potential increase in surface area from spreading – for example, contact adhesives generate vapour at a much greater rate after they have been spread over a surface, and complex metal parts may have quite an extensive covering of solvent after they have been removed from a degreasing bath.



• The Position of the Extraction Fans

The important factor which controls the positioning of the extraction fan unit is the density of the contaminant. The vapours given off by many common solvents are heavier than air, therefore they tend to layer over the lowest floor area in the workplace. For such conditions, fans should be positioned in the walls at a low level. Where the vapour is lighter than air then the contaminant will rise; for this situation the fan must be positioned high on the workplace walls or in the roof.

A major problem in setting up an efficient dilution ventilation system is the formation of dead areas. These are areas in the workplace which, owing to the air-flow pattern produced by the extraction fan and the inlet of make-up air, remain dormant and so the air is not changed. Dead areas can be detected by the use of smoke tracer tubes. A high density of smoke will remain in the unventilated areas.

A secondary problem with dead areas is that they can move from one position in the workplace to another. Such moves can be produced by changing the inlet for the make-up air – for example, in cold weather the inlet may be spread over the workplace via the cracks in windows and doors. In hot weather, indiscriminate opening of doors and windows will produce a quite different flow pattern. Moving the position of machinery or workbenches can also cause the same problem. To help reduce the problem, controlled air make-up inlets can be constructed.

Where large quantities of air are being used to carry out the dilution process then consideration must be given to recycling heat losses from the workplace. It can be achieved by using heat exchange systems whereby make-up air is heated by the exhausted air.

Respiratory Protective Equipment Purpose, Application and Effectiveness

Personal protection involves the use of systems designed to be worn by personnel to help reduce the possibility of harm from the hostile environment in which they are working. This is called a safe person strategy. Ideally, the safe person strategy is a second line of defence against a potential hazard – control at source, or a safe place strategy, should be the first aim.

However, there are situations where personal protection is the only, or the most appropriate, method to deal with a particular hazard – for example, when the cost of controlling the hazard at source is high and the time required for protection is short. Classic situations which typify these conditions are:

• Work involving planned maintenance – for example, during plant shut-downs or deluging asbestos-covered boilers.

• Failure of primary safety systems or emergency situations – for example, a chemical leak from totally enclosed plant, or exposure to a smoke-filled building during a fire.

As a generalisation, the need for personal protection during normal working should be avoided. However, there will always be some exceptions to this rule, and protective footwear, headgear, hand protection and special clothing are worn during most, if not all, of the working time in some cases.

The Personal Protective Equipment (PPE) at Work Regulations 1992 (as amended) bring all types of PPE, from gloves to breathing apparatus, under a single set of regulations. The main general requirements are as follows:



• Employers must ensure that suitable PPE is provided where workers may be exposed to a risk to their health and safety, unless such risks have been adequately controlled by other means which are equally or more effective.

• PPE is not suitable unless it is appropriate for the risks and the conditions where exposure to the risk may occur, and is effective in preventing or controlling those risks. It must also take account of ergonomic requirements – being capable of fitting the wearer, taking adjustments into account.

• In circumstances where more than one risk to health and safety occurs, and where workers have to wear more than one type of PPE, the employer must ensure that such equipment is compatible and remains effective.

• Before PPE is supplied, the employer must carry out an assessment of its suitability. This should include risks unavoidable by other means (PPE is always a last resort), and a definition of the characteristics required to meet identified needs.

• PPE must be maintained in efficient working order by defined maintenance at a specified frequency or, where appropriate, by a programme of regular replacement. It must also be stored safely when not in use.

• Employees must be provided with appropriate information, instruction, training and supervision to ensure that PPE is effectively used.

Types of Respiratory Protective Equipment (RPE) An important point to note about respiratory protection is that there are two fundamentally different types:

• Respirators, which are designed to purify respirable air by inhaling it through a medium which removes the contaminants. There are five types of respirator and selection depends on the nature of the hazardous substance, the purifying medium (such as filtration for dust particles, or absorption for gases and vapours), how well it purifies the air (efficiency, protection factor) and leakage of contaminant into the respirator (face fit, seals, etc.).

• Breathing apparatus, which supplies pure respirable air from an uncontaminated source – by means of a hose supplying uncontaminated air, compressed air from cylinders or a compressor, or as a self-contained unit carried by the user.

Filtering Face-Piece Respirator

This type of respirator consists of a piece of filtering material worn over the nose and mouth and secured by twin elastic headbands. Fit around the chin and face depends on the tension in the headbands; a flexible metal strip enables the user to bend it over the bridge of the nose to effect a personal fit.

Filtering Face-Piece Respirator

The simple structure is designed to provide a cheap, disposable unit. They are generally light and comfortable to wear, permit ease of breathing and speech, do not interfere excessively with vision and can be worn with eye protection. There are various types




Cartridge

Non-return exhaust valve

Facepiece

available, offering protection against nuisance dusts, nuisance odours and certain toxic vapours and corrosive vapours depending on the type of filter fitted.

There are some practical disadvantages in that an adequate face-fit test cannot be carried out, face seal cannot be fully achieved over beards or a few days’ growth, and used respirators need a safe disposal procedure. Chemically contaminated respirators may require special treatment.

Ori-nasal or Half-Mask Respirator

Half-mask respirators are made with a flexible rubber or plastic face-piece which covers the nose and mouth, to which is fixed a replaceable cartridge capable of removing the airborne contaminant during inhalation of respirable air. Some respirators have a single cartridge, others have twin cartridges. The respirator is supported in the operating position by flexible headbands. Exhaled air is released through non-return exhaust valves.

Half-Mask Respirators – Single and Twin Cartridge Types

Face seal is achieved in good quality respirators by the use of a pneumatic cushion around the outer edge. As with disposable respirators, beards and unshaven faces reduce face-fit efficiency.

Half-mask respirators can be used for protection against dusts, fumes, gases and vapours. Cartridges can be obtained for dust/gaseous state protection either together or separately. There are specific types of cartridge for specific hazards, and they are often colour-coded to help reduce the possibility of incorrect use.

Owing to their quite substantial structure, breathing is often not easy (especially as the filter gets clogged), speech communication is reduced and vision is slightly impaired, especially in twin-cartridge types.

A serious problem which arises with the use of cartridge filters is knowing when their working life has ceased. They need to be tested under working conditions to determine when they have lost their ability to provide protection.

Full-Face or Canister Respirator

Full-face respirators, as the name suggests, are designed to cover the mouth, nose and eyes. They are made of a flexible rubber or plastic face-piece which seals under the chin, around the cheeks and across the forehead. They have replaceable gas-absorbent canisters which are either fitted directly to the face-piece, like a single cartridge half-mask, or connected via a flexible corrugated rubber breathing tube. The canister in this case is supported in a harness. The face-piece is secured to the head by a set of flexible, adjustable headbands. Wide vision is provided in most modern face-masks by a large tough Perspex visor.


Canister Respirators – Attached Directly to Face-Piece and by Flexible Tube

The canister filling is able to absorb, or convert by chemical means, the harmful contaminant so the respirable air is safe to inhale. As with cartridges, the canister fillings are designed to deal with specific hazards and it is important to use the correct one for the hazard encountered. Again, colour coding is generally used to help reduce incorrect use.

The working life of the canister depends on the concentration of the contaminant and the time of use. Manufacturers’ instructions specify minimum canister life for given conditions and generally the maximum contaminant concentration in which the canister should be used. Respiration rate is also important; high work rates during use will soon reduce the capacity of the protective filling. Once canisters have been unsealed, their capacity declines. Canisters also have a shelf life, so maintenance, storage and issue are important in their safe use, as are training of users and their supervision.

Canister respirators are useful as a respiratory protection system, provided the conditions under which they are to be used are known within fairly close limits. To guard against possible over-exposure, some form of alarm system should be used to support their safe use. Doubts must be raised about the use of canister respirators for rescue or escape in gassing accidents. Their use could increase the casualty list, not reduce it – breathing apparatus sets would be more appropriate for both rescue and escape.

Powered Clean-Air Respirator

This type of respirator may be considered as one step up in terms of efficiency on half- or full-face respirators in that the respirator air is pumped into the face-piece.

The main advantage of this system is that the pump provides a positive air pressure during breathing, which reduces user fatigue, allows longer work periods between rests and reduces the risk from ingress of contaminants through leaks in the system.

The systems are mainly designed for protection against dusts, claiming 95% removal of respirable range particles, but filters giving protection from vapours are also available.

Powered clean-air respirators cannot be used in oxygen-deficient atmospheres. The units require special planned maintenance with the increase in operating components, as well as fully trained users. Supervision is, of course, required for effective use.

Powered Visor Respirator

This is a development of the powered clean-air respirator. Purified air is blown down over the user’s face behind a protective visor. The technique frees the user from a ‘sealed’ unit, allowing a more comfortable fit, and is less restrictive to movement. In addition, the helmet and visor give added protection to the head, eyes and face.



Airstream Anti-Dust Helmet

In principle, the helmet’s operation is similar to a household vacuum cleaner. Contaminated air is drawn by a motorised fan into the air intake at the back and passes through an elongated filter bag in the crown of the helmet. The decontaminated air is then directed over the face into the breathing zone where inhalation can take place without any undue effort. Such helmets are highly efficient in removing dusts, but cannot be used for dust immediately hazardous to health or gaseous contaminants, or in oxygen-deficient atmospheres.

Breathing Apparatus

Breathing apparatus can be classified under three general headings.

• Fresh Air Hose Apparatus

Fresh air hose apparatus can be described as a breathing apparatus which provides a supply of unpressurised fresh air from an uncontaminated source to give respiratory protection independent of the atmosphere which surrounds the user. It can therefore be used in toxic and oxygen-deficient atmospheres.

The user is connected to a fresh air supply by an air hose of up to 20 metres and draws air through simply by breathing. The system is not self-contained, so it enables work to be carried out over an indefinite period, provided it is only a short distance from fresh air.

The apparatus usually consists of a full-face mask with a short length of hose secured to the user and to which is connected the main air hose. This is securely fixed in the ground or tied to a permanent structure so the free end is kept clear of the ground and is not pulled into the contaminated atmosphere.

Note that airflow can be affected by ‘pressure drop’ as it flows through a pipe, and this is increased by any kinks and bends in the hose. Thus, an operator may breathe quite easily when the air hose is laid out straight, but after having trailed around obstructions in a real situation, breathing may be impaired and work rates considerably reduced.

• Compressed Airline Apparatus

Compressed airline breathing apparatus is similar in design to fresh air systems but the respirable air comes from a compressed air source. The compressed air supply may be from a cylinder or from a compressor – cylinders provide a mobile supply unit, whereas compressors are more usual in static situations, e.g. pneumatic hammers, air grinders.



As the supply uses higher pressures than fresh air systems, much smaller and longer supply hoses can be used – up to 80 m for some units. The airline can be connected via a pressure-reducing valve to full or half face-piece respirators, hoods, coverall suits or protective visors. Positive pressure helps to reduce work-rate fatigue and the ingress through leaks of harmful airborne contaminants.

Compressed airline systems give complete respiratory protection in dusty, toxic and oxygen-deficient atmospheres.

• Self-Contained Apparatus

Self-contained breathing apparatus provides air or oxygen to the user from cylinders or some other form of container which is carried in a harness on the user’s chest or back. The system provides respiratory protection in toxic, corrosive, dusty and oxygen-deficient atmospheres.

There are three main types of self-contained breathing apparatus, classified mainly on the basis of duration and use:

− Escape sets that have a limited supply of compressed air lasting about ten minutes.

− General breathing apparatus with a larger cylinder of compressed air lasting up to 45-60 minutes at normal working rates.

− Oxygen sets, used for medical purposes (and perhaps in certain specialised applications).

Selection, Use and Maintenance The selection of appropriate respiratory protection is based on three main criteria:

• Type of hazard – whether the hazard is dust, corrosive or toxic substances, or oxygen deficiency, etc.

• Contaminant concentration – the extent to which filters can reduce the concentration to a safe level, or complete protection is required.

• Wearer acceptability – the extent to which users are able to use the system comfortably whilst undertaking the work. To give full protection, respiratory protection systems must be worn during all of the time the hazard is encountered. Poor wearer acceptability may result from misting visors, unbalanced strain upon the head and neck muscles, a feeling of head discomfort (possible headaches) from headbands, difficulty with breathing and conversation, overheating of the area around and covered by the face-piece, excessive sweating and possible dermatitic response, to name but a few. There is a high probability that the protection will be removed during use by a user to gain some relief from such discomfort.

All PPE must be maintained in efficient working order by defined maintenance at a specified frequency, or by a programme of regular replacement where appropriate.

Other Protective Equipment and Clothing PPE must also be provided where there is a risk of contamination through routes of entry other than inhalation.

Gloves Gloves and gauntlets are designed to protect the user from harm caused by external agents. There are specific types of such protection for use with different types of hazard, and it should never be assumed that one type will offer protection against other hazards.



Protective gloves and gauntlets are available for:

• Chemical agents – such as acids, alkalis and solvents.

• Biological agents – such as viruses, fungi and bacteria.

• Physical agents – such as asbestos fibres, lead dust, radioactive dust and dust contaminated by other agents, as well as where there is a risk of contamination in the use of syringes and knife blades (for example, sewage workers cleaning filters or abattoir workers).

Overalls and Footwear Basically, the same principles apply for overalls as for gloves. Specialised overalls, aprons and other forms of clothing, such as leggings, are available to offer protection from a similar range of hazards.

Where hazardous chemicals are used, footwear needs to be impermeable to them. No one material is resistant to all chemicals, but good quality leather boots are most commonly worn. Rubber boots or wellingtons are suitable for some chemicals, and have a longer life in wet environments. They can be washed repeatedly if it is necessary to prevent the spread of contamination, and are often the preferred material for protection against biological hazards. In the manufacture of pharmaceuticals, it is likely that overshoes will be used to prevent the spread of contamination.

There might be other considerations to be taken into account as well. If flammable atmospheres exist, then precautions have to be taken against static discharges by having conducting soles so the charges can leak away to earth. Some chemicals, if spilled on the floor, can produce a slippery surface, so a non-slip sole is advantageous. Hot materials, especially molten tar, require heat resistant footwear, probably worn together with gaiters.

(Briefly digressing from chemical hazards, protective footwear is often required as a precaution against a wider range of hazards: steel toe caps where there is a risk of falling objects, steel in-soles to protect against standing on sharp objects, thermally insulated boots for work in cold environments, forestry boots for chainsaw users, and boots with ankle support for anyone traversing uneven ground.)

Eye Protection Protection is required from hazards which can cause damage to the eyes, such as handling or coming into contact with acids, alkalis and corrosive or irritant substances, using any gas or vapour under pressure, or working in contaminated dusts. The protection should be extended to all persons who may be at risk, not just to those operating the particular processes.

Various forms of eye protection are available, depending on the type of hazard encountered:

• Spectacles

These provide limited protection against liquids and sprays, and may be used where the potential risks are low – for example, in general chemical laboratories. Side pieces extend the protection offered. They are not effective against dusts and vapours.

Spectacles provide the least of the problems associated with eye protection – reduction in visual field, misting and becoming dirty or scratched. Also, where safety spectacles provide adequate protection, the use of sight-corrected or prescription lenses is possible.



• Goggles

These provide full eye enclosure and this offers almost complete protection for the eyes from all the potential hazards which occur from dusts, vapours and liquids.

The basic design of goggles consists of a one-piece, clear visual section in front of the eyes surrounded by a safe, flexible frame which seals across the forehead, around the temple and the cheekbone and over the bridge of the nose. The effectiveness of the protection usually depends on the fit under the eyes and over the bridge of the nose.

It also allows operators to wear their own prescription spectacles under the goggles. This does cause a small problem in that the side seal over the temples may be reduced.

Vision is more restricted than with spectacles and misting over of the eyepiece becomes a problem.

• Face Visors

These provide both eye and face protection and will be used where the risk arises from splashes of liquid which may be harmful to the skin. They are secured by an adjustable head frame or may be fixed to a safety helmet.

It is important that users of eye protection have access to lens cleaning and demisting facilities – either of their own or at cleaning stations. Self-maintenance by users has been found to improve the wearer acceptability of eye protection.

Personal Hygiene and Protection Good welfare facilities need to be provided. Hot running (where possible) water, soap and a means for drying must be provided. With more serious hazards, showers and nail brushes may be required. Barrier creams may also need to be provided if required. Not preparing or eating food in work areas will help control the hazard of ingestion.

If warranted by the risk assessment, vaccinations may also be required. However, this depends on the availability of suitable antigen (vaccine) to produce immunity (via antibodies) in the potentially infected worker. So, for example, vaccines are available for Hepatitis B but not for AIDs.

Health Surveillance The objectives of health surveillance where employees are exposed to substances hazardous to health in the course of their work are:

• The protection of the health of individual employees by detection as soon as possible of any adverse changes which may be attributed to exposure to substances hazardous to health.

• To assist in the evaluation of measures taken to control exposure.

• The collection, maintenance and use of data for the detection and evaluation of hazards to health.

• To assess, in relation to specific work activities involving micro-organisms hazardous to health, the immunological status of employees.

Thus, the purpose of routine health surveillance is to identify, at as early a stage as possible, any variations in the health of employees which may be related to working conditions.



Where hazards are low and the likelihood of occupational disease remote, there may be no necessity for a system of regular health checks. Nevertheless, it is recommended that basic personal records should be kept for all employees, including a historical record of jobs performed, details of periods of exposure to harmful agents, absence due to sickness or injury, and cause or duration of absence. Where hazards are low but there is known to be the possibility of occupational disease leading to easily recognisable symptoms, self-checks may be acceptable. For medium range hazards, checks by a responsible person, such as a supervisor, first-aider or nurse, may be required.

Where there appears to be a higher level of risk, an assessment of the level of surveillance required should be made with the assistance of an occupational physician. These ‘higher-level’ checks may include:

• Biological effect monitoring – the measurement and assessment of early biological effects in exposed workers.

• Medical surveillance – clinical examinations and measurements of physiological and psychological effects of exposure to hazardous substances in the workplace, as indicated by alterations in body function or constituents.

• Enquiries about symptoms – inspection or examination by a suitably qualified person.

• Review of records and occupational history during and after exposure, to check correctness of the assessment of risks to health and to indicate if the assessment requires a review.

Examples of the substances and processes which may give rise to identifiable health effects and for which health surveillance measures must be carried out include:

• Substances of recognised systemic toxicity – monitored by appropriate clinical or laboratory investigations.

• Substances known to cause occupational asthma – monitored by enquiries seeking evidence of respiratory symptoms related to work.

• Substances known to cause severe dermatitis – monitored by skin inspection by a responsible person.

• Contact with chrome solutions in electrolytic plating or oxidation of metal articles by use of an electrolyte, in dyeing processes, or in processes of liming and tanning of raw hides and skins – monitored by skin inspection by a responsible person.

Pre-Employment Health Screening In certain circumstances, pre-employment health screening may be appropriate to ensure that employees are fully fit at the outset and able to perform their work efficiently in the conditions:

• For new employees, or those being transferred from one type of work to another, if it is considered that the work is hazardous to health.

• Where the worker has to enter a hazardous environment to which he or she has not previously been exposed.

• Where there is a high risk of accidents to employees or others, such as in transport.

• Where there is a risk of endangering others through transmission of infection.

• Where the work entails high standards of physical or mental fitness.

Tests and procedures for pre-employment health screening should relate to the demands of the work and the potential hazards it presents and may include vision, hearing and lung function.



Records of pre-employment health screening will provide a base-line measurement of an individual’s health, which can be used as a comparison for any subsequent health testing.

Further Controls for Carcinogens, Asthmagens and Mutagens The Control of Substances Hazardous to Health Regulations 2002 details in Regulation 7(3) a hierarchy of measures to be adopted where it is not reasonably practicable to prevent exposure to carcinogens or mutagens. Regulation 7(4) states that this includes safe handling and transport, suitable maintenance, reducing the number of persons exposed and their individual exposures, reducing the quantity of the substance, general ventilation and hygiene measures.

Regulation 7(5) addresses exposure to carcinogens or mutagens and states that where it is not reasonably practicable to prevent exposure, further measures should be adopted in addition to those identified in subsections 3 and 4.

These are:

• Totally enclosing the process and handling systems, unless this is not reasonably practicable.

• The prohibition of eating, drinking and smoking in areas that may be contaminated by carcinogens.

• Cleaning floors, walls and other surfaces at regular intervals and whenever necessary.

• Designating those areas and installations which may be contaminated by carcinogens or mutagens and using suitable and sufficient warning signs.

• Storing, handling and disposing of carcinogens or mutagens safely, including using closed and clearly labelled containers.

The ACoP emphasises this further by stating that whether or not it is reasonably practicable to totally enclose the process and handling systems, then all the other measures are still required.



CONTROL OF HAZARDOUS DUSTS

Carcinogens, Mutagens and Asthmagens A carcinogen is an agent (either physical or chemical) that has the ability to produce malignant tumours.

It is defined in COSHH as a substance or preparation (i.e. a mixture of two or more substances) which is classified for labelling purposes as carcinogenic, category 1 or 2 and carrying the risk phrases R45 “May cause cancer”, or R49 “May cause cancer by inhalation”.

Carcinogens attack the mechanism controlling replication and repair of normal tissue. They cause change in cellular DNA. Abnormal cells are produced which divide uncontrollably and produce growth of cancerous (or malignant) tissue. The cells grow rapidly, invade and affect the surrounding tissue.

The action of carcinogens differs from ordinary toxic action:

• They upset the fundamental cell reactions within the cell structure, whereas other toxic substances generally upset the metabolic processes and prevent cells from functioning normally.

• They demonstrate irreversible effects which continue after cessation of exposure to the carcinogen. The action of ordinary toxic agents usually stops when the exposure ceases, and recovery generally follows.

The effects of a carcinogenic agent may not manifest for periods between five and 50 years depending on the nature of the agent and the affected tissue. During this time, there is little or no warning of the eventual malignant outcome.

Examples of common carcinogens include:

• Tars and polycyclic aromatics occurring in coal tar, asphalt, creosote and mineral oils, with the potential to cause skin cancer.

• Asbestos (particularly blue asbestos), encountered in lagging, building trades and dockyards, which on inhalation may cause lung cancer or mesothelioma (malignant tumours of the pleura (lung cavity) or peritoneum (abdominal cavity)).

• Wood dust is associated particularly with cancer of the nasal cavities and paranasal sinuses, as well as of the nasopharynx, the larynx and with Hodgkin's Disease (a form of lymphatic cancer).

A mutagen is a physical or chemical agent that causes, or increases the rate of, changes or mutations in the genetic material (DNA) of a cell or tissue and thus increases the frequency of mutations above the natural background level. Cellular damage may sometimes be passed to future generations, i.e. inheritable genetic effects. DNA damage may go on to cause cancer. All carcinogens are therefore also mutagens, but not all mutagens are carcinogens.

They are defined in COSHH as a preparation or substance which is classified for labelling purposes as mutagenic category 1 or 2 and carrying the risk phrase R46 ”May cause heritable genetic damage”.

Most mutations have an adverse effect on the living organism leading to cancer or immediate death of the cell.

An example of a mutagen is potassium dichromate, which is used in explosives, safety matches, dye manufacture and photography. It is also a carcinogen.



Refer back to the section on Further Controls for Carcinogens, Asthmagens and Mutagens to remind yourself of the control measures contained in Regulation 7 of COSHH.

An asthmagen is defined in the COSHH ACoP (L5, Appendix 3) as a substance which is known to cause occupational asthma if, due to workplace exposure, it both produces a hypersensitive state in the airways and triggers a subsequent reaction.

In the occupational setting, such substances are often known as respiratory sensitisers. Common examples are wood dusts (both hard and soft woods), isocyanates, glues, resins, solder/colophony fume, stainless steel welding fume and azodicarbonamides (plastics and rubber).

HSE aims to ensure that all duty holders reduce exposure to asthmagens by achieving adequate control. COSHH Regulation 7 (7) states that control can only be considered to be adequate when:

• The principles of good practice have been met, and

• Any WEL is not exceeded, and

• Exposure is reduced to the lowest level reasonably practicable.

Duty holders need to have a management system in place that identifies the agent, assesses the risk and, if exposure cannot be prevented, then adequately controls it. COSHH, Regulation 9, requires that all engineering controls are maintained and systems of work and supervision are reviewed at suitable intervals. There should be suitable information, instruction and training. When employees are exposed, then health surveillance should be provided.

Hazardous Dusts Lead Where there is exposure to lead compounds, dust, fume or vapour at work then the employer must:

• Assess the risks of lead exposure and decide if the exposure is significant and what precautions are needed to protect health.

• Put in place safe systems of work and controls, e.g. exhaust ventilation equipment.

• Provide washing and changing facilities, and places to eat and drink which are free from contamination with lead.

• Provide information to employees about the risks of working with lead and precautions that employees should take.

• Provide training on the use of control measures and the use of PPE.

If exposure to lead is significant, then the employer also has to:

• Provide protective clothing.

• Measure airborne lead levels and inform staff of the results.

• Provide RPE if levels exceed the prescribed WEL.

• Provide health surveillance with a service to quantitate the levels of lead in the blood and inform employees of the results.

If blood lead levels exceed 50 μg/dl (the action level) the employer must reduce the level to below the action level by:



• Reviewing control measures and checking that they are fully functional.

• Making sure that the employees are following correct hygiene procedures.

• Consulting a medical practitioner about additional protective measures.

If levels exceed 60 μg/dl, this may lead to the employee being suspended from the work.

Silica In 2006 HSC set a new WEL for respirable crystalline silica (RCS) of 0.1 mg/ m3.

Consequently, this figure should not be exceeded, but in practice, however, employers will be expected to keep exposures well below 0.1 mg/ m3. More importantly, employers are expected to apply good control practice, as well as getting below the WEL.

Because silica dust has been identified as a carcinogen, and because of the link to chronic obstructive pulmonary disease (COPD), levels should be as low as reasonably practicable.

The COSHH Regulations require employers to:

• Apply the eight principles of good practice for the control of substances hazardous to health (regardless of whether an exposure limit has been assigned).

• Ensure that the WEL is not exceeded.

• Ensure that exposure to substances that can cause occupational asthma, cancer, or damage to genes that can be passed from one generation to another, is reduced as low as is reasonably practicable.

Specific precautions employed should involve:

• Assessment

COSHH requires that the health risk is assessed and then prevented or controlled. If dust levels are significant, then atmospheric sampling of atmospheric dust and respirable silica should be employed.

• Elimination and Substitution

A first step is to substitute silica with other materials, e.g. use of non-silica grit for blasting operations. It may also be possible to get rid of or reduce the need for scabbling, cutting or drilling concrete through design.

• Control of Dust

It may be feasible to control respirable silica by dust suppression techniques or LEV. Tools are available which are exhaust ventilated to remove dust at source and are fitted with a water supply for dust suppression.

• PPE

If existing control techniques are not appropriate or do not reduce exposure sufficiently, then RPE may have to be provided as well.

Those who wear PPE should be adequately trained in its use and limitations.



• Welfare Facilities

Facilities for washing and changing should be available on site. Workers should wash their hands before eating, drinking and using the toilet. Eating and drinking should take place away from the working area.

• Health Surveillance

Where workers are exposed to respirable crystalline silica levels of greater than 0.1 mg/m3 8-hour TWA, then health surveillance which includes a respiratory questionnaire, lung function testing and chest X-rays should be provided.

Fibres (MMMF) The COSHH Regulations require that employees’ exposure to all hazardous substances is prevented or, if this is not reasonably practicable, adequately controlled.

General PPE can only be used if it is not reasonably practicable to use other measures, e.g. local exhaust ventilation.

The following general precautionary measures might not apply in all circumstances and should be adapted for local conditions. Precautions should be regularly reviewed to ensure that they remain adequate, particularly if circumstances change.

• Prevention

Perhaps a substitute, non-fibrous material can be used.

Dust suppressants, non-fibrous bonding materials or coating the product with a protective sealant should be considered.

• Engineering Controls

It may not be practicable to use LEV or total enclosure on some construction sites. Also remember that exhaust air from LEV should not be re-circulated into a workplace, unless effectively filtered.

Frequent visual checks and thorough examinations should be periodically carried out by competent persons to ensure that efficiency of the extraction equipment is being maintained. LEV plant should be thoroughly examined and tested at least once every 14 months and a record kept for at least five years after the date on which it was made.

• Work Planning/Housekeeping

Potential sources of airborne dust arise from settled dust, waste and off-cut insulation materials. These can be controlled by good housekeeping. There should be frequent clearing up of waste and offcuts, and immediate cleaning should take place after dusty work has been completed to reduce dust or fibre exposure. Cleaning should be by a dustless method, e.g. vacuum cleaning. Dry material should be thoroughly wetted before being swept up or brushed away.

• General PPE

RPE and protective clothing should only be used when all other reasonably practicable measures have been taken but have not achieved adequate control.



Asbestos The regulations governing all work with asbestos on workplace premises are the Control of Asbestos Regulations 2006. The regulations and controls are more fully described in a later section; here we give an overview of methods for the control of asbestos.

The control measures for work with asbestos include restricting access to the area, sealing off the area, testing the sealed area for leaks, providing appropriate protective equipment (coveralls, respirators) and a decontamination unit, thoroughly cleaning the area and obtaining a clean air certificate after a successful air test upon completion of the work.

For work involving asbestos you must, where it is reasonably practicable to do so:

• Identify the type of asbestos (by analysis or otherwise) before commencing work.

• Enclose the work area and keep it under negative pressure.

• Use controlled wet removal methods (e.g. water injection, damping down the surface to be worked on). Dry removal processes are unacceptable.

• Use a wrap-and-cut method or glove bag technique (a method of removing asbestos from pipes, ducts, valves, joints and other non-planar surfaces).

• Where appropriate use measures which control the fibres at source, for instance, by using vacuuming equipment directly attached to tools. Failing this, use equipment hand-held by a second employee right next to the source emitting the fibres (known as ‘shadow vacuuming’).

Cement Dust Employers should first consider using elimination or substitution to prevent contact with cement. Otherwise, control measures should be applied which minimise skin contact from contaminated surfaces in the construction environment.

• Washing the skin with warm water and soap or other skin cleanser and drying the skin afterwards is an important method of controlling cement dermatitis. Adequate facilities for drying clothes and changing clothes should be provided.

• Gloves may help to protect the skin from the effects of cement but may not be suitable for all aspects of construction work as cement may become trapped inside the glove against the skin.

• PPE, including overalls with long sleeves and trousers, should be provided.

• Health surveillance is needed to protect individuals and identify skin conditions at an early stage in order to treat the condition and give advice. It also gives an early warning of lapses in control.

Health surveillance of a simple type is normally adequate. A trained, competent person should carry out skin inspections at regular intervals. Health care professionals may be needed to devise a health surveillance regime and train the “responsible person” to carry out skin inspections. Findings of skin inspections should be reported to the employer who will then refer the worker to a suitably qualified person.

• The employer must keep health records. They must also provide information to the employees and provide instruction and training on the nature of health risks likely to be encountered and the precautions necessary.



Wood Dust Hardwood and soft wood dusts both have a WEL of 5mg/m3 and must not be exceeded. Because wood dust is an asthmagen, exposure must be reduced as low as is reasonably practical.

Key controls:

• LEV must be provided to extract dust at woodworking machines.

• The LEV and collection system must be maintained for efficient working.

• Under COSHH, a competent person must examine the LEV at least every 14 months.

• Wood dust should be cleared up using a vacuum system. Such systems should be suitable and have a HEPA filter.

• RPE as well as LEV should be used for particularly dusty tasks.

• Airlines or dry sweeping should be avoided when clearing away wood dust as it can cause high peaks of dust exposure.

• During health surveillance, any adverse health effects in staff should be detected early, as wood dust is an asthmagen.

• Low levels of health surveillance are adequate for most wood dusts and consist of a questionnaire used before work starts and then repeated on an annual basis.

• Higher levels of health surveillance, including lung function testing, are needed for exposures to western red cedar wood which is a known asthmagen.

Asbestos The main regulations governing all work with asbestos on workplace premises are the Control of Asbestos Regulations 2006. The Regulations bring together in to one regulatory package the three previous sets of regulations covering the prohibition of asbestos, the control of asbestos at work and asbestos licensing. They cover all those people who are liable to be exposed to asbestos and place an explicit duty to manage asbestos on employers in non-domestic premises. (No decision has been taken yet relating to domestic premises.)

The Regulations prohibit the importation, supply and use of all forms of asbestos. They continue the ban introduced for blue and brown asbestos in 1985 and for white asbestos in 1999. The ban applies only to new use of asbestos. If existing asbestos-containing materials are in good condition, they may be left in place, provided their condition is monitored and managed to ensure they are not disturbed. However, the second-hand use of asbestos products, such as asbestos cement sheets and asbestos boards and tiles, including panels which have been covered with paint or textured plaster containing asbestos, is banned.

The most important changes from the Control of Asbestos at Work Regulations 2002 are:

• A lower control limit of 0.1 fibres per millilitre of air measured over four hours.

• Work with textured coatings will, generally, not need to be done by a licensed contractor. It will still need to be done safely by trained, competent people working to certain standards.

• Employers can no longer carry out work in their own premises with their own workers without a licence if the work would otherwise require a licence.



Also, the new Regulations are clearer that suitable training is required for anyone who may be exposed to asbestos.

Asbestos has been extensively used as a heat insulating material in lagging of pipes and tanks, and in wall and loft insulation. Asbestos cement has been widely used in panels, particularly for roofing but also for walls, and has also been used as pipework. Because of its inertness and lasting properties, asbestos has been used in ceiling tiles, and textured finishes. Sprayed asbestos coating on steel members gives improved fire resistance and prevents corrosion. Other applications of its use were in gaskets, packing plugs and asbestos rope.

Identification Asbestos or asbestos-containing material (ACM) cannot readily be recognised even by experienced professionals, and laboratory testing of samples is often required to ascertain whether materials do contain asbestos. Recognition is also more difficult when ACM is concealed by other means, e.g. decorations or coatings. Consequently, a major problem facing workers is that often they do not know when and where they may encounter asbestos in their work. ACMs may be present if the building was constructed or refurbished before blue and brown asbestos were banned in 1985, and asbestos cement was used up until 1999.

The three main types of asbestos that have been used commercially are:

• Crocidolite (blue).

• Amosite (brown).

• Chrysotile (white).

The type of asbestos cannot be identified just by its colour, but requires microscopic examination in a laboratory.

Some products have one type of asbestos in them while others have mixtures of two or more. All are dangerous, but blue and brown asbestos are known to be more dangerous than white. There has been some controversy as to whether white asbestos is safe, though this is disputed by the HSE, on the basis of evidence from the International Agency for Research on Cancer that it is considered to be a category 1 human carcinogen. In any case, there is good reason for adopting a precautionary approach with chrysotile, as it often contains small quantities of the other forms.

Surveys Whoever has control of a building has a duty to manage the asbestos in their building. This starts with taking reasonable steps to find out if there are materials containing asbestos in the premises and, if so, how much, where they are and what condition they are in. This can – but does not have to – involve a survey. A survey can be:

• Type 1 – presumptive. This is to locate materials assumed to contain asbestos and note what condition they are in. No sampling is done.

• Type 2 – sampling. This is the same as type 1 but samples are taken and analysed to confirm whether asbestos is present.

• Type 3 – full access. This involves getting full access to all parts of the building, using destructive inspection if necessary. This type is usually used just before demolition or major refurbishment.

The results of all types of survey, including information on the accessibility, condition and surface treatment of any presumed or known ACMs, should be recorded and the



information provided to anyone who may work on, or disturb, these materials. Safety representatives are entitled to this information.

Consulting others, such as architects, employees or safety representatives, may provide more information. If the age of the building or the information obtained provides strong evidence that no ACMs are present, then you need only to record why this evidence indicates there is no asbestos present.

If there is doubt whether asbestos is present, it shall be presumed that it is present and also that it is not restricted to white asbestos, and the Regulations shall apply accordingly.

Assessment The Control of Asbestos Regulations 2006 state that an employer shall not carry out work which is liable to expose his employees to asbestos unless he has:

(a) Made a suitable and sufficient assessment of the risk created by that exposure to the health of those employees and of the steps that need to be taken to meet the requirements of these Regulations;

(b) Recorded the significant findings of that risk assessment as soon as is practicable after the risk assessment is made; and

(c) Implemented the steps referred to in sub-paragraph (a) above.

Where asbestos is concerned, employers must assess the risk of exposure and then do all that is reasonably practicable to avoid the risk, thereby ensuring the health and safety of employees and others. If an ‘asbestos incident’ occurs, all employees should be informed in writing about their potential exposure and the possible risks to health; and the fact of their exposure must be recorded by the employer.

Requirements for Removal Provided asbestos is well contained in structural elements (e.g. cement, tiles), and is left undisturbed and not subject to drilling, sawing or unscrupulous demolition, the risk is small compared to the risk of removing it. Experience in other countries has shown that systematic removal measures are very expensive, with no objective improvement in health. France and the USA adopted a management and control strategy and concluded that improper removal might cause a problem where none existed.

Though the HSE is stressing that in many cases asbestos can be retained and managed, some employers take the approach that eventually it will have to be removed when its condition deteriorates, so it might as well be removed immediately thereby avoiding wasted money on maintenance in the interim. Specialist contractors might also advocate the same strategy as that will be financially advantageous to them in the short term.

Where asbestos is to be removed, then a number of controls apply covering notification, licensing of operators and procedures.

Licensing

Most asbestos removal work must be undertaken by a licensed contractor but any decision on whether particular work is licensable is based on the risk. Work is only exempt from licensing if:

• The exposure of employees to asbestos fibres is sporadic and of low intensity (but exposure cannot be considered to be sporadic and of low intensity if the concentration of asbestos in the air is liable to exceed 0.6 fibres per cm3 measured over 10 minutes); and



• It is clear from the risk assessment that the exposure of any employee to asbestos will not exceed the control limit; and

• The work involves:

− Short, non-continuous maintenance activities. Work can only be considered as short, non-continuous maintenance activities if any one person carries out work with these materials for less than one hour in a seven-day period. The total time spent by all workers on the work should not exceed a total of two hours, including time spent on constructing enclosures and cleaning.

− Removal of materials in which the asbestos fibres are firmly linked in a matrix, such as asbestos cement, textured decorative coatings, vinyl floor tiles, roofing felt and gaskets.

− Encapsulation or sealing of asbestos-containing materials which are in good condition.

− Air monitoring and control, and the collection and analysis of samples to find out if a specific material contains asbestos.

Unless work meets one of the exemptions above, then it must be undertaken by a contractor licensed by the HSE Licensing Unit.

Notification

If the work is licensable, at least 14 days’ notice to the enforcing authority (or such shorter time as the enforcing authority may agree) is to be given. The notification (as per Schedule I of the 2006 Regulations) should contain:

• The name of the notifier and the address and telephone number of his usual place of business.

• Location of the work site.

• A description of the type of asbestos to be used or handled (crocidolite, amosite, chrysotile or other).

• The maximum quantity of asbestos to be held at any one time on the premises at which the work is to take place.

• The activities or processes involved.

• The number of workers involved.

• Measures taken to limit the exposure of employees to asbestos.

• The date of commencement of the work activity and its expected duration.

Plan of Work

No work with asbestos shall be undertaken without a written plan of work detailing how that work is to be carried out. The plan shall be kept at the premises at which the work is being carried out for such time as that work continues. In cases of final demolition or major refurbishment of premises, the plan will usually require that asbestos shall be removed before any other major works begin.

The Regulations require the measures for managing the risk are to be specified in the written plan, including:

• Monitoring the condition of any asbestos or any substance containing or suspected of containing asbestos.

• Ensuring any asbestos or any such substance is properly maintained or where necessary safely removed.



• Ensuring that information about the location and condition of any asbestos or any such substance is provided to every person liable to disturb it, and made available to the emergency services.

The measures specified in the plan must be implemented and recorded.

The plan is to be reviewed and revised at regular intervals, and forthwith if there is reason to suspect that the plan is no longer valid, or there has been a significant change in the premises to which the plan relates.

Information, Instruction and Training The Regulations require mandatory training for anyone liable to be exposed to asbestos fibres at work (see Regulation 10). This includes maintenance workers and others who may come into contact with or who may disturb asbestos (e.g. cable installers) as well as those involved in asbestos removal work.

Every employer shall ensure that adequate information, instruction and training is given at regular intervals to those of his employees who are or who are liable to be exposed to asbestos, or who supervise such employees, so that they are aware of:

• The properties of asbestos and its effects on health, including its interaction with smoking.

• The types of products or materials likely to contain asbestos.

• The operations which could result in asbestos exposure and the importance of preventive controls to minimise exposure.

• Safe work practices, control measures, and protective equipment.

• The purpose, choice, limitations, proper use and maintenance of respiratory protective equipment.

• Emergency procedures.

• Hygiene requirements.

• Decontamination procedures.

• Waste handling procedures.

• Medical examination requirements.

• The control limit and the need for air monitoring.

Employees should be made aware of the significant findings of the risk assessment, and the results of any air monitoring carried out, with an explanation of the findings.

Control Measures When work with asbestos or which may disturb asbestos is being carried out, the Asbestos Regulations require employers and the self-employed to prevent exposure to asbestos fibres. Where this is not reasonably practicable, they must make sure that exposure is kept as low as reasonably practicable by measures other than the use of respiratory protective equipment, and ensure that the number of his employees who are exposed to asbestos at any one time is as low as is reasonably practicable. The spread of asbestos must be prevented. The Regulations specify the work methods and controls that should be used to prevent exposure and spread.

The measures shall include, in order of priority:



• The design and use of appropriate work processes, systems and engineering controls and the provision and use of suitable work equipment and materials in order to avoid or minimise the release of asbestos; and

• The control of exposure at source, including adequate ventilation systems and appropriate organisational measures, and the employer shall so far as is reasonably practicable provide the employees concerned with suitable respiratory protective equipment in addition to the measures already mentioned.

Worker exposure must be below the airborne exposure limit (control limit). The Asbestos Regulations have a single control limit for all types of asbestos of 0.1 fibres per cm3. A control limit is a maximum concentration of asbestos fibres in the air (averaged over any continuous 4 hour period) that must not be exceeded.

In addition, short term exposures must be strictly controlled and worker exposure should not exceed 0.6 fibres per cm3 of air averaged over any continuous 10 minute period using respiratory protective equipment if exposure cannot be reduced sufficiently using other means.

Work methods that control the release of fibres such as those detailed in the Asbestos Essentials task sheets for non-licensed work should be used.

Typical control measures for removing asbestos include:

• Restricting access to the area.

• Enclose the work area and keep it under negative pressure, testing the sealed area for leaks.

• Use controlled wet removal methods (e.g. water injection, damping down the surface to be worked on). (Dry removal processes are unacceptable.)

• Use a wrap-and-cut method or glove bag technique (a method of removing asbestos from pipes, ducts, valves, joints and other non-planar surfaces).

• Where appropriate use measures which control the fibres at source, for instance, by using vacuuming equipment directly attached to tools. Failing this, use equipment hand-held by a second employee right next to the source emitting the fibres (known as ‘shadow vacuuming’).

• Thoroughly cleaning the area and obtaining a clean air certificate after a successful air test upon completion of the work.

• Providing a decontamination unit.

A clearance certificate for re-occupation may only be issued by a body accredited to do so. At the moment, such accreditation can only be provided by the United Kingdom Accreditation Service (UKAS).

Respiratory Equipment Respiratory protective equipment is an important part of the control regime but it must not be the sole measure used to reduce exposure and should only be used to supplement other measures.

Suitable respiratory protective equipment should be provided for employees if asbestos fibres in the air have been reduced to as low as is reasonably practicable by using control methods at source, but exposures are still liable to be above the control limits.

The respiratory equipment provided must be marked with a ‘CE’ symbol and matched to:

• The exposure concentrations (expected or measured).



• The job.

• The wearer.

• Factors related to the working environment.

Respiratory protective equipment must be examined and tested at suitable intervals by a competent person, and a suitable record kept for five years. Respirator testing involves daily checks, monthly checks, and full performance checks every 6 months. Operator checks would involve fit testing to see that the correct size and model are used to provide an adequate face seal.

Protective Clothing The Control of Asbestos Regulations 2006 require the provision of adequate and suitable protective clothing for employees exposed or liable to be exposed to asbestos, unless no significant quantity of asbestos is liable to be deposited on the clothes of the employee while he is at work.

When selecting and using protective clothing for work with asbestos, all employers must ensure they comply with the Personal Protective Equipment Regulations 2002 and the Personal Protective Equipment at Work Regulations 1992 (as amended). In general, these regulations require that personal protective equipment (PPE) including clothing must be provided when an employee is exposed to a risk, and that the PPE must be appropriate to the risks involved. It must fit correctly, be compatible (i.e. the wearing of a hard hat must not interfere with the correct fit of a respirator), be in good repair or replaced as necessary. Adequate storage facilities must be provided. Employees must know the risks and be trained in the use of the personal protective equipment. PPE supplied/purchased for use at work must carry the ‘CE’ mark of approval.

You should note that protective clothing used in an asbestos environment will not prevent the body or underclothes from being contaminated with asbestos fibres, or remove the necessity to cleanse and decontaminate the body after the protective clothing is removed.

Protective clothing normally required in asbestos removal/encapsulation operations will depend on the risk assessment and will include:

• Coveralls – these must have an elasticated hood and elasticated cuffs at the wrists and ankles. There should be no external pockets. Two types of coverall are used:

− Disposable coveralls - suitable for the majority of asbestos removal tasks.

− Non-disposable coveralls.

• Head protection – this should be to EN 397 for hard hats and EN 812 for bump caps. When worn, it must not affect the correct fit of the respirator, and provide protection to operatives from other risks.

• Footwear – overshoes or safety/Wellington boots (ensure the trouser legs of the coveralls are outside the boots). Any footwear used within the enclosure must be easily decontaminated.

• Underclothing/socks/gloves – use disposable clothing.

The methods of decontamination might include a safe system of work, positive pressure respirators, and transit procedures. Transit footwear must be appropriate to the site conditions and, if used previously in the enclosure, properly decontaminated. Working coveralls are for wearing in the enclosure, and transit coveralls are for transit between the enclosure and the hygiene facility.



Laundering Safe arrangements must be made for the laundering of all reusable protective clothing.

However, it may prove difficult to locate suitable commercial laundries as research has shown that few commercial laundries will launder asbestos clothing/towels.

No contaminated clothing should be taken home, including underclothing. Safe arrangements must be made to transfer and launder contaminated clothing in dissolvable bags which are suitably identified by an appropriate warning label. Cases of residual asbestos have been found even after laundering possibly due to ineffective decontamination procedures. However, laundering was effective in removing asbestos from coveralls.

Contaminated disposable clothing should be treated as asbestos waste and dealt with appropriately (see later).

Air Monitoring Air sampling is used for compliance sampling (i.e. within control or action limits), background sampling prior to work commencing, leak sampling to ensure adjacent or adjoining areas are not above background levels, and clearance sampling after asbestos removal and cleaning has taken place prior to handover to occupiers.

Sampling should be carried out by trained staff in compliance with the Approved Code of Practice (5th edition).

Examination of samples by polarised light microscopy will usually indicate the presence of asbestos and its type. It is not possible to identify the type of asbestos by its visual colour alone. The examinations should be undertaken by suitably trained and accredited analysts from laboratories.

Sampling should take place while activity in the area is representative of that occurring in normal occupancy or use, and should be undertaken by specialists in compliance with HSE Guidance Note EH 10, Asbestos: Exposure Limits and Measurement of Airborne Dust Concentrations, and the approved methods outlined in MDHS 39/4, Asbestos Fibre in Air: Sampling and Evaluation by Phase Contrast Microscopy (PCM).

Employers must monitor the exposure of their employees to asbestos by measurement of asbestos fibres present in the air at regular intervals. The method is set out in the publication Determination of airborne fibre concentrations. A recommended method, by phase-contrast optical microscopy (membrane filter method), WHO Geneva 1997 (ISBN 92 4 154496 1).

An individual employee may have access to his personal monitoring record, copies of which are provided to the HSE.

Dutyholders may choose to employ an asbestos surveyor/inspector to carry out the assessment of whether asbestos is present in their premises. The accreditation schemes are run by the United Kingdom Accreditation Service (UKAS).

Medical Surveillance Every employer shall ensure that for each of his employees who is exposed to asbestos:

• A health record is available for at least 40 years from the date of the last entry made in it.

• The record is maintained (unless the exposure of that employee does not exceed the action level).



• The employee is under adequate medical surveillance by a relevant doctor (unless the exposure of that employee does not exceed the action level).

The medical surveillance required includes a specific examination of the chest and:

• A medical examination not more than two years before the beginning of such exposure.

• Periodic medical examinations at intervals of not more than two years (or such shorter time as the relevant doctor may require while such exposure continues).

• A certificate is issued to the employer and employee stating that the employee has been so examined and the employer must keep that certificate or a copy for at least four years from the date on which it was issued.

Requirements for Disposal Any waste containing asbestos is classed as a controlled waste under the Environmental Protection Act (EPA) 1990 and, dependent upon its source and properties, may also be classified as hazardous waste, under the Hazardous Waste (England and Wales) Regulation 2005. Under these regulations, all movements of hazardous waste by a licensed carrier have to be tracked, by means of a consignment note system, until it reaches a suitable waste management facility. Under the Environmental Permitting Regulations 2007, all controlled waste – including asbestos waste – must be kept, treated or disposed of at a site permitted to accept such waste. Although in some circumstances, e.g. for some recovery operations, sites do not need to be licensed, a waste management permit is required for all sites wishing to handle asbestos waste. The permit will indicate that asbestos waste can be handled, and also set out terms and conditions to prevent harm to human health and pollution to the environment. All asbestos is disposed of by landfill. The Environmental Permitting Regulations 2007 allow asbestos, depending upon its categorisation, to be accepted at hazardous waste sites and also at non-hazardous waste sites in separate cells. Those sites that can accept asbestos operate special procedures to ensure safe disposal.

Every employer who undertakes work with asbestos must ensure that raw asbestos or waste which contains asbestos is not stored; received into or despatched from any place of work; or distributed within any place of work, except in a totally enclosed distribution system, unless it is in a sealed container clearly marked showing that it contains asbestos. Raw asbestos must be labelled in accordance with the provisions of the appropriate regulations above.



WASTE DISPOSAL AND CONTROL OF POLLUTION Pollution is the contamination or damage caused by human activity to the environment. It arises in respect of three aspects of the environment:

• Atmospheric pollution – fumes, smoke and dust are discharged into the air from land clearing, incinerators, traffic exhausts, demolition and working with toxic materials.

• Water pollution – liquid waste (effluent) containing toxic, or otherwise harmful, substances such as detergents discharged into ground water, rivers or sea-water directly from sewers, factories or surrounding land (such as fertilisers being washed away from farm land by the rain). Construction sources of water pollution include diesel, oil, paint, solvents, cleaners and other hazardous substances. Construction debris and dirt also contribute.

• Land pollution – solid waste deposited on land, atmospheric deposition, run-off from spoil heaps, spillages and leaks from industrial processes, and agricultural practices or where materials are deposited on land, e.g. the application of pesticides or large scale spillages of diesel fuels and lubricants.

There are a number of legislative provisions relating to the environment. Those that we would consider to be key to environmental control are the Environmental Protection Act 1990, Environmental Permitting Regulations 2007 and the Water Resources Act 1991.

The basic principle of pollution control established by the Environmental Protection Act (EPA) 1990 but now covered by the Environmental Permitting Regulations 2007 is that if a substance, on discharge into the environment, could cause harm or is capable of causing harm to humans or the environment, then both the substance and the process of making it are normally subject to regulation. This is likely to be in the form of a permit issued by an enforcing body, depending on the nature of the process, the substance to be discharged, and the medium into which it is discharged. Permits for waste management sites are also now controlled under these regulations.

Discharges to controlled waters – i.e. territorial, coastal, inland and ground waters – which are not regulated under the EPA are regulated under the Water Resources Act 1991.

Environmental Issues Specific to Construction and Demolition Activities Construction and demolition activities, by their very nature are noisy and dirty. Quite often the work is of short duration, but it can still cause significant disruption in local communities. Some of the commonly occurring problems reported in relation to construction sites are noise, dust, bonfire smoke and land contamination. They will consequently cause pollution to the air, water and the land.

Noise Construction activities produce a lot of noise, mainly from vehicles, heavy equipment and machinery, but also from people shouting and radios turned up too loud. Excessive noise is not only annoying and distracting, but can lead to hearing loss, high blood pressure, sleep disturbance and extreme stress. Research has also shown that high noise levels disturb the natural cycles of animals and reduces their usable habitat.

We will be discussing noise in detail in Element 9.



Dust Dust generated from construction activities is usually dealt with as a statutory nuisance under the EPA.

High levels of dust are commonly generated from concrete, cement, wood, stone and silica and can carry for large distances over a long period of time. Construction dust is usually particulate matter less than 10 microns in diameter (known as PM10) and is invisible to the naked eye. As we have seen earlier in this element, such particles penetrate deeply into the lungs and cause a wide range of health problems including respiratory illness, asthma, bronchitis and cancer.

Diesel engine exhausts of vehicles and heavy equipment are another major source of PM10 on construction sites. This is known as diesel particulate matter (DPM) and consists of soot, sulphates and silicates, all of which readily combine with other toxins in the atmosphere, increasing the health risks of particle inhalation. Diesel is also responsible for emissions of carbon monoxide, hydrocarbons, nitrogen oxides and carbon dioxide. Noxious vapours from oils, glues, thinners, paints, treated woods, plastics, cleaners and other hazardous chemicals that are widely used on construction sites also contribute to air pollution.

Bonfire Smoke All trade, industrial and construction sites have tight laws relating to what they are allowed to burn.

They are subject to the laws of the Clean Air Act and waste management regulations. Any site that creates black smoke by burning rubber, plastics or similar materials may produce emissions that contain some very toxic gases. Usually fires that are giving off thick, but white or grey smoke are probably not committing any offence.

Land Contamination There is increasing pressure for new developments to re-use so-called “brownfield” sites, i.e. sites that have previously been developed. Consequently, previous pollution of the land may put the use of the site at significant risk and the developer may arrange for a full land quality survey to be undertaken as part of a planning application. Such a survey should address such problems as how the pollution can be dealt with. It is usual for planning conditions from the local authority to require written confirmation of the proposed clean-up methods to be employed by the developer.

Water Pollution Land clearance can often lead to soil erosion which in turn leads to silt-bearing run-off and sediment pollution. Such silt and soils entering natural waterways make the water turbid, restrict the entry of sunlight and destroy aquatic life.

Similarly, surface water run-off also carries pollutants from the site, such as diesel, oil, toxic chemicals, and cement. When these substances enter the waterways they become toxic to aquatic life and any animal that drinks from water. Pollutants on construction sites can also soak into the groundwater, a source of human drinking water. Once contaminated, groundwater is much more difficult to treat than surface water.

Waste Wastes generated by construction projects are numerous and can include for example, asbestos, asphalt, bricks, rubble and timber.

The Site Waste Management Plans Regulations 2008 require construction projects over a certain size to prepare a waste management plan prior to construction work



starting. These plans require an examination of the types and quantities of wastes produced, options for reducing, reusing and recycling wastes and an estimate of cost savings associated with effective waste management.

Integrated Pollution Prevention and Control Regime The Environmental Permitting Regulations 2007 address the Pollution Prevention and Control Regime which was originally introduced by the Environmental Protection Act 1990. The regime aims to permit industrial installations with a view to controlling the release of polluting substances into the air, land and water. It also aims to control noise, energy use and environmental incidents. The most polluting of the installations (Part A1) are enforced by the Environment Agency, the less polluting (Part A2) are enforced by local authorities. Those installations with polluting potential to the air only (Part B) are enforced by local authorities.

Schedule 1 to the regulations lists all of the processes that require a permit and also lists those substances that are released to air, for example sulphur dioxide and dust, or to water, for example, Arsenic and metals that are of particular concern. Any processes that are listed in the schedule require a permit and it is a criminal offence to operate without a permit. Permits are likely to specify conditions in order to minimise the environmental impact.

Processes included in the regime are numerous and are likely to include food manufacturer’s, larger paint sprayers, combustion processes including incineration, landfill sites and many others.

To gain a permit for an installation an operator will be required to meet the following:

• All appropriate preventative measures are taken against pollution, in particular through the application of Best Available Techniques (BAT). BAT not only covers the technology used, but also the way in which the installation is operated, to ensure the highest level of environmental protection as a whole. It also takes into account the balance between the costs and environmental benefits.

• If a process involves releases to more than one environmental medium, the operator must use the Best Practicable Environmental Option (BPEO) to achieve the best environmental solution overall. This means that the applicant must show that, given a number of techniques available at similar cost, the one achieving the best overall environmental result will be adopted.

• No significant pollution is caused.

• Waste production is avoided and where waste is produced, it is recovered. Where that is not possible it is disposed of in a way producing the least impact on the environment, if any impact is produced at all.

• Energy is used efficiently.

• Measures are taken to avoid accidents and limit their consequences.

• Necessary measures are taken on the closure of an installation to avoid any pollution risk and return the site to a satisfactory condition.

The powers of EA and local authority inspectors in respect of enforcing the conditions of the authorisation are essentially the same as those of HSE and local authority inspectors – they can enter premises, make investigations, issue improvement and prohibition notices and instigate legal proceedings.



Water Pollution Water pollutants include:

• Non-degradable pollutants – man-made plastics, metals (lead, mercury) and metallic objects.

• Biodegradable pollutants – sewage, household waste, water-soluble or suspended substances such as detergents.

The prime objective in seeking to ensure that water is not polluted is the very obvious basic human need for clean drinking water. However, there are other environmental issues relating to the quality of the water in our rivers, lakes and seas – particularly in respect of the need to retain the biodiversity of aquatic species (both fish and plants) and to maintain the supply of food that these species provide for mankind. In addition, man uses water extensively for recreational and industrial purposes and the quality of water is an issue here too. Finally, water is often used to disperse and dilute other pollutants and must, therefore, be relatively free from pollution before this can occur.

Regulation of the industry is conducted in accordance with the provisions of the Water Act 1989 and the Water Resources Act and Water Industry Act both of 1991. The main regulatory and enforcement body is the Environment Agency (EA), which is responsible for the protection of water resources and river quality.

Control over water pollution is based on a system of water discharge consents, obtained from the EA under the Water Resources Act 1991. These apply in respect of any discharge of trade effluent or sewerage effluent into controlled waters. Controlled waters cover, essentially, all moving water, including inland and underground waters and estuaries, as well as the actual river bed and, in certain circumstances, territorial and coastal waters.

Information supplied when applying to the EA for such a consent must include the nature of the discharge, quality and rate of flow. The procedure is, though, more public – including more extensive advertising and more information being made available in the public register.

The actual policy of enforcement is linked to the setting of standards in respect of both emission limits and receiving water quality limits for different uses or objectives. An offence will take place in respect of each separate discharge by a company resulting in the entry of prescribed materials into controlled waters, unless a consent exists or there is some other defence.

Pollution Prevention There are three key elements to any effective pollution prevention strategy:

1. Prevent emissions to the environment, for example:

− By redesigning processes to eliminate the use, generation or release of hazardous substances.

− By utilising ‘clean technology’, e.g. replacing solvent cleaning with an ultrasonic process.

− By ensuring storage tanks are adequately bunded to contain leaks and releases (see below).

− By ensuring that effective spillage procedures are in place (see below).

− By the use of interceptors, traps, sumps, etc. to prevent the release of oils and fuels to drainage systems.

− By regular maintenance and inspection of equipment.



− By establishing effective management procedures – including monitoring and review.

2. Minimise or reduce emissions to the environment to acceptable levels and

3. Render harmless any emissions to the environment.

The various means of prevention against pollution fall broadly into two categories, managerial means and practical means.

An Environmental Management System involves the adoption of a policy with risk assessment, operating procedures and training programmes.

Practical measures include identification of drains to separate surface and foul water wherever possible. Other practical measures include bunding and use of spill kits.

• Bunds

Bulk storage of chemicals and oil is a frequent source of pollution. The main means of protecting water from these potential pollutants is by bunding at the storage site. Bunds should be sturdily constructed and lined with material impervious to the stored resource. They should be made of a base with surrounding wall to contain any spills.

• Spill Kits

Provision of a spill kit in case of emergency is sound practice. They should be appropriate to the substance being stored. Training in their use must be given. Such kits must be strategically placed and accessible for use. Typical kits contain gloves, absorbent materials, shovels, brooms, plastic bags, etc.

Waste Disposal The general approach to waste disposal should take account of a hierarchy of waste management options:

• Waste reduction – the primary emphasis should be on not producing waste in the first place, by process change and optimising process efficiency.

• Reuse – for example, returnable glass bottles.

• Recovery of waste – including recycling (such as glass, metal and paper), composting and incineration with energy recovery.

• Disposal – generally to landfill.

Regulatory Framework Duty of Care

The Environmental Protection (Duty of Care) Regulations 1991 were enacted under the Environmental Protection Act 1990 and introduced a new duty of care for all persons involved in the generation, importation, handling, transportation and disposal of waste. The duty identifies the responsibility for waste management from the generation of waste to its final disposal to lie with the company generating or importing the waste.

Consequently, the duty of care extends from those producing waste through transporters of waste to its final disposal.

Particular emphasis is placed upon preventing any other person contravening the law as to unauthorised deposits, treatment or disposal of the waste.



This requirement places a duty on producers of waste to ensure that their wastes are transported and disposed of in accordance with the provisions of the duty of care.

Classification of Waste and Regulatory System

Part II of the EPA deals with the regulation of waste products and materials. Under this, waste is classified in two main ways:

• Controlled waste – defined as household, industrial and commercial waste or any substance which is scrap, effluent or unwanted surplus from a process. The Environmental Permitting Regulations 2007 apply to such waste.

• Hazardous waste – defined as waste which may be so dangerous or difficult to treat, keep or dispose of that special provision is required for dealing with it. The Hazardous Waste (England and Wales) Regulations 2005 apply to any such waste.

Non-hazardous waste refers to materials which are not covered by the above description of hazardous waste and includes household waste, paper, wood and other biodegradable materials.

As with other regulatory systems, waste management is controlled through a licensing system, operated by the Environment Agency (EA). A waste management licence is required by any operator who wishes to keep, treat or dispose of controlled waste. This system allows for more integrated control as the EA also deals with water and IPPC, especially as the latter does not deal with the final disposal of waste to land. The greater integration supports the development of a national waste strategy and compliance with the packaging rules, both required by EC law.

Local authorities are the waste collection authorities responsible for arranging for all collection of controlled waste, including recycling, either themselves or by a private company under contract. Collected waste is then passed to the appropriate waste disposal authority – usually the county council or some joint authority in the large cities. Waste disposal authorities, as their name makes clear, have the duty to ensure the effective and sustainable removal, storage and final disposal of waste. They are also the hazardous waste authority and have the main role in dealing with contaminated land.

Hazardous Waste The Hazardous Waste (England and Wales) Regulations 2005 were introduced to replace the Special Waste Regulations 1996. Hazardous wastes are listed with an asterisk in the List of Wastes (England) Regulations 2005 and include things like prescription medicines, toxic substances and NiCad batteries.

The regulations require that a producer of hazardous waste be registered with the Environment Agency or exempted. Exempted producers are those that produce hazardous waste, but in quantities of less than 200 kg per year. This exemption is limited to only some producers such as offices.

Each batch of hazardous waste must be accompanied by a consignment note throughout each stage of the journey from the producer to final disposal and the duty falls on the producer to ensure that other duty holders, such as carriers and disposers, fulfil their duties appropriately.

The regulations ban the mixing of different categories of hazardous waste, or the mixing of hazardous waste with non-hazardous waste, unless this is authorised by permit or licence.

Hazardous waste must be characterised before it can be accepted at landfill sites and this may require sampling and analysis of every load of waste in some industries.



Landfill Currently about 60% of controlled waste goes to landfill, but under EC pressure, targets have been set to reduce controlled waste going to landfill to 33% and increase recovery of MSW (municipal solid waste) to 67% by 2015. A landfill tax, based on quantity of materials deposited, has been introduced to discourage excessive use.

Landfill site management must adequately control and minimise any hazards arising from the site, and this has implications both during filling and afterwards. An Environmental Impact Assessment under the Environmental Permitting Regulations 2007 and under planning law will be needed before a permit is granted, and must take into account all aspects of the operation, the kind of waste to be disposed of and any other treatment.

Landfill sites are classified according to the types of waste they are permitted to accept: Inert; Non hazardous; and hazardous waste sites.

The major hazards are fire and contamination of groundwater, but risks may also arise in the form of noise, odours, dust, litter and vermin. All these must be adequately controlled, especially if the site is anywhere near a populated area.

• Obviously, fire is highly undesirable – producing smoke, offensive smells and contaminated leachate and often being difficult to extinguish once it becomes established. The major cause of fire is landfill gas – a combustible mix of methane and carbon dioxide – which can also cause explosions, as well as presenting a toxic hazard to premises near the site by permeating through soil. It is fed largely by municipal solid waste which contains sufficient putrescibles to give a good supply, with production often continuing for in excess of ten years. Such gas may be odourless and a programme of monitoring is essential. Landfill gas is normally collected in pipes laid within the waste and is either flared off or collected and used as fuel. Energy from landfill gas is a way of reducing the national requirement for fossil fuels and in the UK, though a small contribution, is nonetheless worth having.

• It is important to prevent contaminants in the site spreading into groundwater. The site must be geologically suitable – ideally by being impervious to water (with a clay or sandstone base), but if not, a membrane can be laid to make it so. The design should minimise ingress of groundwater due to changes in the local water table, flood conditions or the existence of springs or streams, and be finished with an impervious clay dome to shed rainwater. A system of porous pipes may be laid to collect and encourage drainage of leachate.

• Noise nuisance may arise due to heavy vehicle movements, both site traffic bringing waste for disposal and site plant. Care should be taken in planning traffic routes, coupled with limitation of acceptance times and on-site use of heavy plant. Licence conditions may specify working hours.

• Odours can be minimised by using the cell method of filling, ensuring that the surface is covered with inert fill at the end of each working day and generally operating to minimise exposed areas. Waste segregation is encouraged so that inert waste is available to build the cell walls and provide cover material. Residual odour problems can be controlled by using masking chemical sprays, and this can be a solution to problems arising in unusual wind conditions.

• Dust and litter can be minimised by damping down and cell filling practice. Chain-link security fences not only keep unauthorised persons out, but also help to catch wind-blown litter.

• Vermin usually appear as gulls which feed on exposed waste, and rats, mice and even foxes. Good site practice as already described can do much to contain the problem of



birds. Netting over the working slope has proved effective and also further controls litter. If rats become a problem, especially having regard to the risk of Leptospirosis (Weil’s Disease), an eradication programme will be necessary.

Cell filling is typically achieved by tipping down a gradual slope and using specially designed plant in the form of steel-wheeled compactors which bury litter and also increase the fill density, maximising the site capacity and minimising later settlement. This also reduces the possibility of fire starting in the waste.

Regulations on landfill are aimed towards reducing the amount of biodegradable waste disposed of in this manner. Additionally, various wastes are required to be segregated for disposal. Certain categories of waste are banned from landfill disposal altogether, including chemical wastes which can be categorised as infectious, explosive, corrosive, inflammable, or are liquid in state.

Composting It is estimated that 30-35% of UK municipal solid waste (MSW) is compostable. The organic component of MSW, the putrescible or biodegradable fraction, can be broken down by aerobic bacterial decomposition to give compost, a fibrous residue which is used as a soil conditioner, organic fertiliser, mulch and potting medium. The process may take several weeks to complete, after which the product is marketable or may be used ‘in-house’ by local authorities’ Parks Departments.

Additionally, garden waste can also be turned into compost and chipping of woody waste can also be carried out to produce mulch.

Compost made from waste which has been separated from the municipal stream inevitably contains some toxic metal content. Surprisingly, much of this originates from house dust, which contains lead. Also, staples, batteries and wine bottle caps are difficult to remove, adding to the problem. Emphasis has gone towards separation at source from the MSW stream.

Incineration Incineration with energy recovery is seen as a possible solution to the waste problem. MSW has about 40% of the calorific value of coal and is therefore a considerable source of energy. Waste reduction is 60-90% and results in clinker (useable for road-building), fly ash (landfilled) and metal (recycled).

The process requires capital-intensive plant and detailed planning. An Environmental Impact Assessment (EIA) is required, mainly because of the problem of air pollution, and the process is covered by Environmental Permitting requirements. However, incinerator technology is now well developed and they run very cleanly. Advanced moving-grate design ensures that the waste dries, then burns efficiently. High temperatures and complete combustion are achieved, followed by gas cleaning which removes fly ash and acid gases (mostly from combustion of the plastic PVC). Production of dioxin is minimised by rapid cooling of stack gases to below the critical temperature range at which formation may occur. There is no visible stack emission when they are operating.




Revision Questions

20. What principles of control are illustrated by the following measures?

(a) Using a substance in another form.

(b) Vacuuming rather than sweeping up.

(c) Job rotation.

(d) Using water-based adhesives rather than solvent-based ones.

21. What is the difference between local exhaust ventilation and dilution ventilation?

22. What are dead areas and why are they a problem for dilution ventilation systems?

23. List the five main types of respirator and the three main types of breathing apparatus.

24. What are the key criteria in the selection of the appropriate respirator to use?

25. What is the main purpose of routine health surveillance?

26. What removal requirements must be met for work with asbestos-containing material?

27. What control measures are required for working with asbestos?

28. What are the disposal requirements for asbestos?

29. What controls are placed on the disposal of hazardous waste?

30. What is the hierarchy of waste management options?


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SUMMARY Chemical hazards arise from the presence of substances or preparations in the form of liquids, gases, vapours, mists, fumes and dusts in the workplace. Biological hazards are in the form of micro-organisms which are directly connected with the work or are associated with the environment in which it is conducted.

Substances and preparations which are hazardous to health must, under the CHIP Regulations, be classified by the category of danger and risk that they present and, on supply, be appropriately labelled and accompanied by a safety data sheet. The CHIP Approved Supply List provides standard categories of danger and associated symbols, and risk and safety phrases for these purposes.

Ill-health effects may be acute or chronic depending on the immediacy of the reaction of the body to exposure to the substance and the time over which exposure takes place.

Hazardous agents commonly found in construction materials and activities are organic solvents, carbon dioxide, carbon monoxide, isocyanates, lead, asbestos, silica, cement dust, wet cement, wood dust, tetanus, leptospira and hepatitis.

Absorption of hazardous substances into the body may take place by a number of routes – inhalation, ingestion, absorption, aspiration and injection. The route of entry will depend on the form of the chemical or biological agent to which a person is exposed, and conditions the type of control measure which is appropriate.

Occupational exposure limits – expressed as either long-term or short-term workplace exposure limits (WELs) – define the acceptable levels of concentration of airborne contamination to which workers may be exposed. HSE Guidance Note EH40 provides the basic source of information about OELs.

Control measures are based on reducing exposure levels to the lowest level reasonably practicable, even where that is below the WEL for airborne contaminants. Monitoring of airborne contamination levels is required to ensure that this is achieved and there are a variety of means of doing this – for example, stain tube detectors and diffusion samplers. In addition, routine and special health checks may be necessary to monitor workers’ exposure to contaminants and ensure that any ill-health effects are identified at the earliest stage.

Control measures for limiting exposure to harmful substances are based on the hierarchy of control – elimination or substitution, process and engineering controls to reduce exposure and segregate workers from the hazards (particularly using local exhaust or dilution ventilation systems) and finally PPE. The main forms of PPE required are respirators and breathing apparatus, and protective clothing. All forms of physical control measures, including PPE, must be subject to a programme of routine inspection, testing and maintenance.

Working with asbestos is covered by the Control of Asbestos Regulations 2006. It involves identification of the type of asbestos, assessment of the risk, conforming with the requirements for removal, the introduction of control measures, and meeting the requirements for disposal.

The discharge of hazardous substances into the environment (i.e. to air, land and water) is primarily controlled by a system of authorisations operated by the Environment Agency and local authorities. The aim is to make sure that, where such discharges are necessary, appropriate measures are taken to ensure that harm to the environment is minimised.

chemical and biological health hazards and control

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