nature of environmental health hazards didi supardi, dr. dept. of public health & preventive...
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Nature of Environmental Health
Hazards
Didi Supardi, dr.
Dept. of Public Health & Preventive Medicine
OBJECTIVE:• To describe the difference between hazard & risk• To explain the logic of the various methods of classifying
environmental hazards• To describe a scheme for identifying the level of hazard &
toxicity• To explain why knowledge of the toxicology,
microbiology, or physical properties of an environmental hazard is essential to determining the most appropriate approach to its risk assessment
• To identify different experimental investigative methods• To explain the biological significance of bio-
transformation process• To list the basic characteristics of chemical, physical,
biological, mechanical, & psychosocial hazards
Required Reading
Yassi A, Kjellström T, de Kok T, Guidotti TL. Basic Environmental Health. Chapter 2: Nature of Environmental Health Hazards. New York: Oxford University Press, 2001
Definition
Hazard a factor or exposure that may adversely affect
health (Last, 1995)
a source of danger a qualitative term expressing the potential of an
environmental agent to harm the health of certain individuals if the exposure level is high enough &/or if other conditions apply
Definition (cont’d)
Risk the probability that an event will occur, e.g. that
an individual will become ill or die within a stated period of time or before a given age; the probability of a (generally) unfavorable outcome (Last, 1995)
the quantitative probability that a health effect will occur after an individual has been exposed to a specified amount of a hazard
Types of EH Hazards Biological hazards
e.g. bacteria, viruses, parasites Chemical hazards
e.g. toxic metals, air pollutants, solvents, pesticides Physical hazards
e.g. radiation, temperature, noise Mechanical hazards
e.g. motor vehicle, sports, home, agriculture, & workplace injury hazards
Psychosocial hazardse.g. stress, lifestyle disruption, workplace
discrimination, effects of social change, marginalization, unemployment
Classified according to: nature natural vs anthropogenic traditional vs modern route of exposure setting
Types of EH Hazards (cont’d)
Traditional Hazards• Disease vectors• Infectious agents• Inadequate housing
& shelter• Poor-quality drinking
water & sanitation• Indoor air pollution
from cooking• Dietary deficiencies• Hazards of child birth• Wildlife & domestic
animals• Injury hazards in
agriculture
Modern Hazards• Tobacco smoking• Transport hazards• Pollution from
sewage & industry• Outdoor air
pollution from industry & motorcars
• Overuse or misuse of chemicals
• Industrial machinery
• Unbalanced diet
Biological, chemical & physical hazards by routes of exposure
Biological Chemical Physical
AIR
Agent/source Microorganisms Fumes, dust, particles Radiation, heat, noise
Vectorial factors Coughing, exhalations Contaminated air Climate, unguarded exposures
Routes Inhalation, contact Inhalation, contact Inhalation, direct penetration
WATER
Agent/source Microorganisms, decayed organic material
Discharges, teaching, dumping
Radiation, heat in power station cooling water
Vectorial factors Insects, rodents, snails, animal excreta, food chain
Contaminated food & water
Accidents, contaminated food & water
Routes Bites, ingestion, contact Ingestion, contact Ingestion, contact
BIOLOGICAL HAZARDSInclude all of the forms of life (as well as the
nonliving products they produce) plants, insects, rodents, other animals, fungi, bacterial,
viruses, protozoa, a wide variety of toxins & allergens; & prion
Routes of exposure:• Air• Water• Food• Direct penetration• Biting
Person exposed the agent distributed via blood, lymph, or other body fluids to the parts of the body most favorable for it to grow
Prions (proteinaceous infectious particles)• Infectious agents (not organisms) made of protein (yet to be fully
characterized)• Multiply by converting normal protein molecules into dangerous
ones by changing their shapes• Responsible for the various forms of spongiform
encephalopathy, e.g.: - bovine spongiform encephalopathy (BSE) or ‘mad-cow’ disease) - Creutzfeldt-Jakob disease (CJD) - kuru (transmitted by ritual handling of bodies & brains of the dead)
• Symptoms of the human prion diseases: dementia, loss of coordination
Viruses• a piece of nucleic acid (either DNA or RNA), which makes
its progeny by orchestrating the production of virus particles by a cell
• viruses that lack a lipoprotein envelope (e.g. hepatitis A, gastroenteritis viruses) can grow in the human gut & be spread by food & water
• viruses with a lipoprotein envelope have limited survival outside a host & so are spread in aerosols or inoculations of body fluids from person to person (e.g. measles)
• reproduces only inside a host cell• viral diseases do not respond to antibiotics, but some
respond to specific antivirals
Bacteria• most have sufficient energy supply to reproduce outside a
cell• have genetic material but no nucleus• divide by splitting in half• exist singly or in short chains of two or more• classified by shape, oxygen requirement & ability to take
up a special stain
Fungi• simple plant plant organisms that lack the chlorophyll
needed to use carbon dioxide & sunlight to build sugars & structural molecules
• classified into yeast (single-celled) or moulds, which grow as branching filaments called hyphae
• yeast reproduce by budding, moulds by branching & longitudinal growth of hyphae, as well as by producing sexual spores
Protozoa• the simplest class of animal & consisting of a single
nucleated cell• each cells has organelles that carry on such functions as
locomotion, nutrition, excretion, respiration• e.g. : plasmodium, cryptosporidium, giardia
Arthropods• the large phylum of animal life that includes insects,
spiders, mites & ticks (as well as crabs & lobsters)• some of these creatures bite, sting, cause allergic
reactions, and may serve as vectors for viruses & other infectious agents
Pathway DiseaseInadequate sanitation, the dumping of untreated sewage into surface water, poor hygienic practices water polluted by human excreta
cholera, typhoid fever, dysentry, other diarrheal diseases, hepatitis A, schistosomiasis
Overcrowding, poorly ventilated housing airborne transmission
tuberculosis, measles, influenza, pneumonia, pertussis, cerebrospinal meningitis
Unhygienic animal husbandry zoonoses transmission
plague & hydatids diseases
Stagnant waters, unsanitary housing, refuse dumping vector-borne transmission
malaria, trachoma, schistosomiasis, filariasis, yellow fever, plague, typhus, trypanosomiasis
CHEMICAL HAZARDS
Inorganic Substances- halogens (e.g. fluorine, chlorine, bromine, iodine)
- alkaline compounds (e.g. NH3, Ca(OH)2, KOH, NaOH
- ozone (O3)
- NOx and SOx
- metals (e.g. cadmium, chromium, copper, lead, manganese, mercury, nickel, arsenic)
Organic Compounds- aliphatic hydrocarbons (e.g. methane, ethane, propane,
butane, pentane, hexane, heptane, octane)
- alicyclic hydrocarbons (e.g. cyclohexane, methylcyclohexane, turpentine)
- aromatic hydrocarbons (e.g. benzene, toluene, styrene, naphthalene)
- halogenated hydrocarbons (e.g. chloromethane, dichloromethane, chloroform, carbon tetrachloride, trichloroethyene, polyviyl chloride)
- alcohols (e.g. methanol, ethanol, propanol)
Route of exposuresSource:• natural events• man-made: industrial, agricultural, commercial,
domestic, manufacturing wastes
Exposure:- inhalation - breastfeeding
- oral ingestion - placental transfer
- absorption via the skin - inoculation & direct penetration
- absorption via the eyes
Air, water,dirt, etc
Food, water,drugsAir
Skin Respiratorytract GI-tract
BloodOtherorgans Liver
Kidney
Sweat Hair Urine Faeces
bileexfoliation
inhalation exhalation ingestion
external contamination
ExposureMedia
Major uptakepathways
Transport &distribution
Majorexcretorypathways
Biotransformation
Hydrophobic or lipophilic hydrophilic
Phase I : - the molecule is altered by the introduction of electrostatically charged (polar) groups
- result of oxidation, reduction, or hydrolysis
Phase II: substances are combined w/ hydrophilic endogenous compounds
Bioactivation of Benzene
O
OH Gluc
Benzene(the original chemical)
Benzene epoxide(a dangerously toxic
product)
Phenol(an intermediate thatthe body can handle)
Phenylglucuronide(hydrophilic; easily
excreted)
Phase I Phase II
xenobiotics
biliary excretion
extracellular mobilization
plasma circulation
renal excretion secretion
phase II(bioinactivation) conjugation
phase I(bioactivation or inactivation)
oxidation, reduction, hydrolysis
accumulation in body fat
lipophilic polar hydrophilichighly lipophilic
metabolically stable
polar
hydrophilic
Toxicityany harmful effect of a chemical or a drug on a target organ
• Systemic toxicity
• Liver toxicity
• Kidney toxicity
• Skin toxicity
• Neurotoxicity
• Immunotoxicity
Chemical agents
Biological agents
Physical agents
DNA
Alteration of geneticcodes & information:- gene mutation- chromosomal alteration- gene rearrangements
Multistage process of carcinogenesis:
Initiation Promotion Progression
• Gene mutation:the result of single or multiple base pair changes (substitutions, deletions, insertions)in the DNA. Normally, the cell defense mechanisms can repair DNA damages, recreatingthe original structures. Repair can be faulty, leading to heritable changes
• Chromosomal alterationsvia damage by genotoxic agents, leading to structural aberrations (breaks, deletions, translocations), &via loss or gain of one or more chromosomes & sometimes changes in the number of chromosomes
• Gene rearrangements: characterized by altered gene expression (gene amplification, loss of activity). The underlying causesmight be translocations or inversions of large parts of chromosomes
Toxicity Testing• Acute toxicity studies
to predict human effects of short-term, high-level exposures; can provide a measure of the toxic potential of different compoundsED50 : dose that would cause the effect in half of the test populationLD50 : dose that would kill half of the test population
LC50 : concentration of gas or vapor that kills half the test population
LD50 & LC50 : crude indices of toxicity
• Sub-chronic testsanimals exposed repeatedly to a given chemical over a relatively long period (28 days or longer), normally 10% of the lifetime of the selected animals
• Chronic toxicity testingperformed by exposing animals to the chemical being tested for the whole of the animal’s lifetime
• Reproductive studieson parents & offspring
Toxicity Testing (cont’d)
• Genotoxic short-term testsshort-term tests for gene mutation & chromosome alterations both in vitro & in vivo
• Human studiesclinical or epidemiological studies
• Structure-activity relationships
Right-to-know legislation hazard identification & control
PHYSICAL HAZARDS
Forms of potentially harmful energy in the environment that can result in either immediate or gradually acquired damage when transferred in sufficient quantities to exposed individuals
e.g.: sound waves, radiation, light energy, thermal energy, electrical energy
Noise
• Noise: an unwanted sound• Sound intensity: measured in decibels (dB)• Risk of incurring hearing loss begins w/
prolonged exposure to sound of + 75 dB(A)• Rule of thumb:
if a loud voice is not understandable at a distance of 1 m b/c of excessive background noise, the background noise level is above 85 dB & likely to be dangerous
Hearing conservation program
• Regular monitoring of the workplace• Baseline & annual audiograms (for all exposed
workers)• In-service & pre-service (worker) education• Systematic record keeping• Worker notification• Provision of hearing protection
Other physical hazards:vibration, radiation, light, lasers, pressure, temperatures
What are potential health effects of such hazards?
Mechanical Hazards
those posed by the transfer of mechanical or kinetic energy (the energy of motion)
Injury, trauma, accidents
Vulnerable groups: children, the elderly, & disadvantaged groups
Psychosocial Hazards
Potential sources of work-related psychosocial stress:
- factors intrinsic to the job
- the role of the worker in the organization
- career development
- interpersonal relationships at work
- organizational structure & climate