qwertyuiopasdfghjklzxcvbnmqwertyuiopasdfghjklzxcvbnmqwertyuiopasdfghjklzxcvbnmqwertyuiopasdfghjklzxcvbnmqwertyuiopasdfghjklzxcvbnmqwertyuiopasdfghjklzxcvbnmqwertyuiopasdfghjklzxcvbnmqwertyuiopasdfghjklzxcvbnmqwertyuiopasdfghjklzxcvbnmqwertyuiopasdfghjklzxcvbnmqwertyuiopasdfghjklzxcvbnmqwertyuiopasdfghjklzxcvbnmqwertyuiopasdfghjklzxcvbnmq

wertyuiopasdfghjklzxcvbnmqwertyuiopasdfghjklzxcvbnmqwertyuiopasdfghjklzxcvbnmqwertyuiopasdfghjklzxcvbnmqwertyuiopasdfghjklzxcvbnmrtyuiopasdfghjklzxcvbnmqwertyuiopasdfghjklzxcvbnmqwertyuiopasdfghjklzxcvbnmqwertyuiopasdfghjklzxcvbnm

MERCURY POLLUTION

INDIAN SCENARIO

M.TECH 1ST SEMESTER- 2010ENVIRONMENTAL ENGINEERING

RITIKA SINGH04/ENV/2010

INDEX

CONTENT page no. Introduction 3

Occurrence 6

Release in the environment 7

Toxicity and safety 12

Mercury in environment 14

Guidance and Awareness Raising Materials under new UNEP Mercury Programs 20

National Threat versus Local Concern 24

Global Threat versus National Concern 26

Mercury Pollution: Indian Scenario 27

Bibliography 28

2

MERCURY (ELEMENT)

INTRODUCTION

Mercury, also known as quicksilver or hydrargyrum is a chemical element with the symbol Hg and atomic number 80. Mercury is the only metal that is liquid at standard conditions of temperature and pressure; the only other element that is liquid under these conditions is bromine. With a freezing point of −38.83 °C and boiling point of 356.73 °C, mercury has one of the broadest ranges of its liquid state of any metal. A heavy, silvery d-block metal, mercury is also one of the five metallic chemical elements that are liquid at or near room temperature and pressure, the others being caesium, francium, gallium, and rubidium.

Mercury occurs in deposits throughout the world mostly as cinnabar (mercuric sulphide), which is the source of the red pigment vermilion, and is mostly obtained by reduction from cinnabar. Cinnabar is highly toxic by ingestion or inhalation of the dust. Mercury poisoning can also result from exposure to soluble forms of mercury (such as mercuric chloride or methyl mercury), inhalation of mercury vapor, or eating seafood contaminated with mercury.

Mercury is used in thermometers, barometers, manometers, sphygmomanometers, float valves, some electrical switches, and other scientific apparatus, though concerns about the element's toxicity have led to mercury thermometers and sphygmomanometers being largely phased out in clinical environments in favour of alcohol-filled, digital, or thermistor-based instruments. It remains in use in a number of other ways in scientific and scientific research applications, and in amalgam material for dental restoration. It is used in lighting: electricity passed through mercury vapor in a phosphor tube produces short-wave ultraviolet light which then causes the phosphor to fluoresce, making visible light.

Properties

Physical properties

Mercury is a heavy, silvery-white metal. As compared to other metals, it is a poor conductor of heat, but a fair conductor of electricity.

Chemical properties

Mercury has an exceptionally low melting temperature for a d-block metal. A complete explanation of this fact requires a deep excursion into quantum physics, but it can be summarized as follows: mercury has a unique electronic configuration where electrons fill up all the available 1s, 2s, 2p, 3s, 3p, 3d, 4s, 4p, 4d, 4f, 5s, 5p, 5d and 6s sub-shells. As such configuration strongly resists removal of an electron; mercury behaves similarly to noble gas elements, which form weak bonds and thus easily melting solids. The stability of the 6s shell is due to the presence of a filled 4f shell. An f shell poorly screens the nuclear charge that increases the attractive Coulomb interaction of the 6s shell and the nucleus (see lanthanide contraction). The absence of a filled inner f shell is the reason for the much higher melting temperature of cadmium. Metals such as gold have atoms with one less 6s electron than mercury. Those electrons are more easily removed and are shared between the gold atoms forming relatively strong metallic bonds.

3

REACTIVITY AND COMPOUNDS

Mercury dissolves to form amalgams with gold, zinc and many other metals. Because iron is an exception, iron flasks have been traditionally used to trade mercury. Other metals that do not form amalgams with mercury include tantalum, tungsten and platinum. When heated, mercury also reacts with oxygen in air to form mercury oxide, which then can be decomposed by further heating to higher temperatures.

Since it is below hydrogen in the reactivity series of metals, mercury does not react with most acids, such as dilute sulphuric acid, though oxidizing acids such as concentrated sulphuric acid and nitric acid or aqua rhezia dissolve it to give sulphate, nitrate, and chloride salts. Like silver, mercury reacts with atmospheric hydrogen sulphide. Mercury even reacts with solid sulfur flakes, which are used in mercury spill kits to absorb mercury vapors (spill kits also use activated carbon and powdered zinc).

Some important mercury salts include:

Mercury (I) chloride (calomel) is sometimes still used in medicine, acousto-optical filters and as a standard in electrochemistry;

Mercury (II) chloride is a very corrosive, easily sublimating and poisonous substance. Mercury fulminate, (a detonator widely used in explosives), Mercury (II) oxide the main oxide of mercury Mercury (II) sulphide (found naturally as the ore cinnabar or vermillion which is a

high-grade paint pigment Mercury (II) selenide, mercury (II) telluride, mercury cadmium telluride and mercury

zinc telluride are semiconductors and infra red detector materials.

In these compounds, mercury displays two oxidation states: +1 and +2. The +1 state oxidation involves the dimeric cation, Hg2

+2. Solutions of Hg2+2 are in equilibrium with Hg2+

and metallic mercury:

Hg2+ + Hg Hg2+2

This equilibrium causes solutions of Hg2+2 to have a small amount of Hg2+ present. Consuming the Hg2+ by another reaction, such as complexation with strong ligands or precipitation of an insoluble salt, will cause all the Hg2+2 to fully disproportionate to Hg2+

and elemental mercury.

Besides Hg2+2, mercury also forms other mercury poly-cation such as Hg2

+3. Higher oxidation states of mercury were confirmed in September 2007, with the synthesis of mercury (IV) fluoride (HgF4) using matrix isolation techniques.

Laboratory tests have found that an electrical discharge causes the noble gases to combine with mercury vapor. These compounds are held together with van der walls force and result in Hg·Ne, Hg·Ar, Hg·Kr, and Hg·Xe. Organic mercury compounds are also important. Methyl mercury is a dangerous compound that is widely found as a pollutant in water bodies and stream.

MERCURY AND ALUMINIUM

Mercury readily combines with aluminium to form a mercury-aluminium amalgam when the two pure metals come into contact. However, when the amalgam is exposed to air, the

4

aluminium oxidizes, leaving mercury behind. The oxide flakes away, exposing more mercury amalgam, which repeats the process. This process continues until the supply of amalgam is exhausted. Because this process releases mercury, a small amount of mercury can "eat through" a large amount of aluminium over time, by progressively forming amalgam and relinquishing the aluminium as oxide.

Aluminium in air is ordinarily protected by a molecule-thin layer of its own oxide, which is not porous to oxygen. Mercury coming into contact with the oxide is not detrimental, although if any elemental aluminium is exposed, the mercury may combine with it and potentially damage the aluminium. For this reason, restrictions are placed on the use and handling of mercury in proximity with aluminium. In particular, mercury is not allowed aboard an aircraft under most circumstances because of the risk of it forming an amalgam with exposed aluminium parts in the aircraft.

ISOTOPES OF MERCURY

There are seven stable isotopes of mercury with 202Hg being the most abundant (29.86%). The longest-lived radioisotopes are 194Hg with a half-life of 444 years, and 203Hg with a half-life of 46.612 days. Most of the remaining radioisotopes have half-lives that are less than a day. 199Hg and 201Hg are the most often studied NMR-active nuclei, having spins of 1⁄2 and 3⁄2

respectively.

HISTORY

Mercury was found in Egyptian tombs that date from 1500 BC. It was also known to the ancient Chinese. In China and Tibet, mercury use was thought to prolong life, heal fractures, and maintain generally good health. One of China's emperors, Qín Shǐ Huáng Dì — allegedly buried in a tomb that contained rivers of flowing mercury on a model of the land he ruled, representative of the rivers of China — was killed by drinking a mercury and powdered jade mixture (causing liver failure, poisoning, and brain death) intended to give him eternal life. The ancient Greeks used mercury in ointments; the ancient Egyptians and the Romans used it in cosmetics which sometimes deformed the face. By 500 BC mercury was used to make amalgams with other metals. The Indian word for alchemy is Rasavātam which means "the way of mercury".

Alchemists thought of mercury as the First Matter from which all metals were formed. They believed that different metals could be produced by varying the quality and quantity of sulphur contained within the mercury. The purest of these was gold, and mercury was called for in attempts at the transmutation of base (or impure) metals into gold, which was the goal of many alchemists.

The element was named after the Roman god Mercury, known for speed and mobility. It is associated with the planet Mercury; the astrological symbol for the planet is also one of the alchemical symbols for the metal. Mercury is the only metal for which the alchemical planetary name became the common name. The mines in Spain, Italy, and Slovenia dominated the mercury production from the opening of the mine.

5

OCCURENCE

Mercury is an extremely rare element in the Earth's crust, having an average crustal abundance by mass of only 0.08 parts per million (ppm). However, because it does not blend geochemically with those elements that constitute the majority of the crustal mass, mercury ores can be extraordinarily concentrated considering the element's abundance in ordinary rock. The richest mercury ores contain up to 2.5% mercury by mass, and even the leanest concentrated deposits are at least 0.1% mercury (12,000 times average crustal abundance). It is found either as a native metal (rare) or in cinnabar and other minerals, with cinnabar (HgS) being the most common ore. Mercury ores usually occur in very young orogenic belts where rock of high density are forced to the crust of the Earth, often in hot springs or other volcanic regions. Mercury is extracted by heating cinnabar in a current of air and condensing the vapor. The equation for this extraction is

HgS + O2 → Hg + SO2

In 2005, China was the top producer of mercury with almost two-thirds global share followed by Kyrgyzstan. Several other countries are believed to have unrecorded production of mercury from copper electron wining processes and by recovery from effluents.

Because of the high toxicity of mercury, both the mining of cinnabar and refining for mercury are hazardous and historic causes of mercury poisoning. In China, prison labor was used by a private mining company as recently as the 1950s to create new cinnabar mercury mines. Thousands of prisoners were used by the Luo Xi mining company to establish new tunnels. In addition, worker health in functioning mines is at high risk.

The European Union directive calling for compact fluorescent bulbs to be made mandatory by 2012 has encouraged China to re-open deadly cinnabar mines to obtain the mercury required for CFL bulb manufacture. As a result, environmental dangers have been a concern, particularly in the southern cities.

Abandoned mercury mine processing sites often contain very hazardous waste piles of roasted cinnabar calcines. Water run-off from such sites is a recognized source of ecological damage. Former mercury mines may be suited for constructive re-use.

6

RELEASE IN THE ENVIRONMENT

Preindustrial deposition rates of mercury from the atmosphere may be about 4 ng /(1 L of ice deposit). Although that can be considered a natural level of exposure, regional or global sources have significant effects. Volcanic eruptions can increase the atmospheric source by 4–6 times.

Natural sources, such as volcanoes, are responsible for approximately half of atmospheric mercury emissions. The human-generated half can be divided into the following estimated percentages:

65% from stationary combustion, of which coal-fired power plants are the largest aggregate source (40% of U.S. mercury emissions in 1999). This includes power plants fueled with gas where the mercury has not been removed. Emissions from coal combustion are between one and two orders of magnitude higher than emissions from oil combustion, depending on the country.

11% from gold production. The three largest point sources for mercury emissions in the U.S. are the three largest gold mines. Hydro geochemical release of mercury from gold-mine tailings has been accounted as a significant source of atmospheric mercury in eastern Canada.

6.8% from non ferrous metal production, typically smelters. 6.4% from cement production. 3.0% from waste disposal, including municipal and hazardous waste, crematoria and

sewage sludge incineration. This is a significant underestimate due to limited information, and is likely to be off by a factor of two to five.

3.0% from caustic soda production. 1.4% from pig iron and steel production. 1.1% from mercury production, mainly for batteries. 2.0% from other sources.

The above percentages are estimates of the global human-caused mercury emissions in 2000, excluding biomass burning, an important source in some regions.

Current atmospheric mercury contamination in outdoor urban air is (0.01–0.02 µg/m3) indoor concentrations are significantly elevated over outdoor concentrations, in the range 0.0065–0.523µg/m3 (average 0.069 µg/m3).

Mercury also enters into the environment through the improper disposal (e.g., land filling, incineration) of certain products. Products containing mercury include: auto parts, batteries, fluorescent bulbs, medical products, thermometers, and thermostats. Due to health concerns (see below), toxics use reduction efforts are cutting back or eliminating mercury in such products. For example, most thermometers now use pigmented alcohol instead of mercury. Mercury thermometers are still occasionally used in the medical field because they are more accurate than alcohol thermometers, though both are being replaced by electronic thermometers. Mercury thermometers are still widely used for certain scientific applications because of their greater accuracy and working range.

The United States Clean Air Act, passed in 1990, put mercury on a list of toxic pollutants that need to be controlled to the greatest possible extent. Thus, industries that release high concentrations of mercury into the environment agreed to install maximum achievable control technologies (MACT). In March 2005 EPA rule added power plants to the list of

7

sources that should be controlled and a national cap and trade rule was issued. States were given until November 2006 to impose stricter controls, and several States are doing so. The rule was being subjected to legal challenges from several States in 2005 and decision was made in 2008. The Clean Air Mercury Rule was struck down by a Federal Appeals Court on February 8, 2008. The rule was deemed not sufficient to protect the health of persons living near coal-fired power plants. The court opinion cited the negative impact on human health from coal fired power plants' mercury emissions documented in the EPA Study Report to Congress of 1998. Historically, one of the largest releases was from the Colex plant, a lithium-isotope separation plant at Oak Ridge. The plant operated in the 1950s and 1960s. Records are incomplete and unclear, but government commissions have estimated that some two million pounds of mercury are unaccounted for. One of the worst industrial disasters in history was caused by the dumping of mercury compounds into Minamata Bay, Japan. The Chisso Corporation, a fertilizer and later petrochemical company, was found responsible for polluting the bay from 1932–1968. It is estimated that over 3,000 people suffered various deformities, severe mercury poisoning symptoms or death from what became known as Minamata disease.

APPLICATIONS

Mercury is used primarily for the manufacture of industrial chemicals or for electrical and electronic applications. It is used in some thermometers, especially ones which are used to measure high temperatures. A still increasing amount is used as gaseous mercury in fluorescent lamps, while most of the other applications are slowly phased out due to health and safety regulations and is in some applications replaced with less toxic but considerably more expensive Galinstan alloy.

PRESENT USE

MEDICINE

Mercury and its compounds have been used in medicine, although they are much less common today than they once were, now that the toxic effects of mercury and its compounds are more widely understood. The element mercury is an ingredient in dental amalgams. Thiomersal (called Thimerosal in the United States) is an organic compound used as a preservative in vaccines, though this use is in decline. Another mercury compound Merbromin (Mercurochrome) is a topical antiseptic used for minor cuts and scrapes is still in use in some countries.

Mercury(I) chloride (also known as calomel or mercurous chloride) has traditionally been used as a diuretic, topical disinfectant, and laxative. Mercury(II) chloride (also known as mercuric chloride or corrosive sublimate) was once used to treat syphilis (along with other mercury compounds), although it is so toxic that sometimes the symptoms of its toxicity were confused with those of the syphilis it was believed to treat. It is also used as a disinfectant. Blue mass, a pill or syrup in which mercury is the main ingredient, was prescribed throughout the 19th century for numerous conditions including constipation, depression, child-bearing and toothaches. In the early 20th century, mercury was administered to children yearly as a laxative and dewormer, and it was used in teething powders for infants. The mercury-containing organohalide merbromin (sometimes sold as Mercurochrome) is still widely used but has been banned in some countries such as the U.S.

8

Since the 1930s some vaccines have contained the preservative thiomersal, which is metabolized or degraded to ethyl mercury. Although it was widely speculated that this mercury-based preservative can cause or trigger autism in children, scientific studies showed no evidence supporting any such link. Nevertheless thiomersal has been removed from or reduced to trace amounts in all U.S. vaccines recommended for children 6 years of age and under, with the exception of inactivated influenza vaccine.

Mercury in the form of one of its common ores, cinnabar, remains an important component of Chinese, Tibetan, and Ayurvedic medicine. As problems may arise when these medicines are exported to countries that prohibit the use of mercury in medicines, in recent times, less toxic substitutes have been devised.

Today, the use of mercury in medicine has greatly declined in all respects, especially in developed countries. Thermometers and sphygmomanometers containing mercury were invented in the early 18th and late 19th centuries, respectively. In the early 21st century, their use is declining and has been banned in some countries, states and medical institutions. In 2002, the U.S. Senate passed legislation to phase out the sale of non-prescription mercury thermometers. In 2003, Washington and Maine became the first states to ban mercury blood pressure devices. Mercury compounds are found in some over-the-counter drugs, including topical antiseptics, stimulant laxatives, diaper-rash ointment, eye drops, and nasal sprays. The FDA has “inadequate data to establish general recognition of the safety and effectiveness,” of the mercury ingredients in these products. Mercury is still used in some diuretics, although substitutes now exist for most therapeutic uses.

COSMETICS

Mercury, as thiomersal, is widely used in the manufacture of mascara. In 2008, Minnesota became the first state in the US to ban intentionally added mercury in cosmetics, giving it a tougher standard than the federal government.

A study in geometric mean urine mercury concentration identified a previously unrecognized source of exposure (skin care products) to inorganic mercury among NYC residents. Population-based bio-monitoring also showed that mercury concentration levels are higher in consumers of seafood and fish meals.

PRODUCTION OF CHLORINE AND CAUSTIC SODA

Chlorine is produced from sodium chloride (common salt, NaCl) using electrolysis to separate the metallic sodium from the chlorine gas. Usually the salt is dissolved in water to produce a brine. By-products of any such chlor alkali process are hydrogen (H2) and sodium hydroxide (NaOH), which is commonly called caustic soda or lye. By far the largest use of mercury. in the late 20th century was in the mercury cell process (also called the Castner-Kellner process) where metallic sodium is formed as an amalgam at a cathode made from mercury; this sodium is then reacted with water to produce sodium hydroxide. Many of the industrial mercury releases of the 20th century came from this process, although modern plants claimed to be safe in this regard. After about 1985, all new chlor alkali production facilities that were built in the United States used either membrane cell or diaphragm cell technologies to produce chlorine.

9

GOLD AND SILVER MINING

Historically, mercury was used extensively in hydraulic gold mining in order to help the gold to sink through the flowing water-gravel mixture. Thin mercury particles may form mercury-gold amalgam and therefore increase the gold recovery rates. Large scale use of mercury stopped in the 1960s. However, mercury is still used in small scale, often clandestine, gold prospecting. It is estimated that 45,000 metric tons of mercury used in California for placer mining have not been recovered. Mercury was also used in silver mining.

OTHER PRESENT USES

Gaseous mercury is used in mercury-vapour lamps and some "neon sign" type advertising signs and fluorescent lamps. Those low-pressure lamps emit very spectrally narrow lines, which are traditionally used in optical spectroscopy for calibration of spectral position. Commercial calibration lamps are sold for this purpose; however simply reflecting some of the fluorescent-lamp ceiling light into a spectrometer is a common calibration practice. Gaseous mercury is also found in some electron tubes, including ignitrons, thyratrons, and mercury arc rectifiers. It is also used in specialist medical care lamps for skin tanning and disinfection (see pictures). Gaseous mercury is added to cold cathode argon-filled lamps to increase the ionization and electrical conductivity. An argon filled lamp without mercury will have dull spots and will fail to light correctly. Lighting containing mercury can be bombarded/oven pumped only once. When added to neon filled tubes the light produced will be inconsistent red/blue spots until the initial burning-in process is completed; eventually it will light a consistent dull off-blue color.

Some medical thermometers, especially those for high temperatures, are filled with mercury; however, they are gradually disappearing. In the United States, non-prescription sale of mercury fever thermometers has been banned since 2003. Mercury is also found in liquid-mirror telescopes. The mirror is formed by rotating liquid mercury on a disk, the parabolic form of the liquid thus formed reflecting and focusing incident light. Such telescopes are cheaper than conventional large mirror telescopes by up to a factor of 100, but the mirror cannot be tilted and always points straight up.

Liquid mercury is a part of popular secondary reference electrode (called the calomel electrode) in electrochemistry as an alternative to the standard hydrogen electrode. The calomel electrode is used to work out the electrode potential of half cells. Last, but not least, the triple point of mercury, −38.8344 °C, is a fixed point used as a temperature standard for the International Temperature Scale (ITS-90).

PROPOSED USES

Liquid mercury has been proposed as a working fluid for a heat pipe type of cooling device for spacecraft heat rejection systems or radiation panels.

HISTORIC USES

Mercury was used for preserving wood, anti-fouling paints (discontinued in 1990), herbicides (discontinued in 1995), handheld maze games, cleaning, and road leveling devices in cars. Mercury compounds have been used in antiseptices, laxatives, antidepressants and in antisyphilitics.

10

Chlor-alkali plants: The largest industrial use of mercury during the 20th century was in large electrolysis batteries for separating chlorine and sodium from brine. The chlorine was used for bleaching paper (hence the location of many of these plants near paper mills) while the sodium was used to make sodium hydroxide for soaps and other cleaning products. This usage has largely been discontinued, replaced with other technologies that utilize membrane cells.

Mercury was used inside wobbler lures. Its heavy, liquid form made it useful since the lures made an attractive irregular movement when the mercury moved inside the plug. Such use was stopped due to environmental concerns, but illegal preparation of modern fishing plugs has occurred. The fresnel lenses of old lighthouses used to float and rotate in a bath of mercury which acted like a bearing.

Mercury blood pressure meter, barometers, diffusion pumps, coulometers, and many other laboratory instruments. As an opaque liquid with a high density and a nearly linear thermal expansion, it is ideal for this role. Liquid mercury was used as a coolant for some nuclear reactor; however, sodium is proposed for reactors cooled with liquid metal, because the high density of mercury requires much more energy to circulate as coolant.

Mercury was a propellant for early ion engines in electric space propulsion systems. Advantages were mercury's high molecular weight, low ionization energy, low dual-ionization energy, high liquid density and liquid storability at room temperature. Disadvantages were concerns regarding environmental impact associated with ground testing and concerns about eventual cooling and condensation of some of the propellant on the spacecraft in long-duration operations. The first spaceflight to use electric propulsion was a mercury-fueled ion thruster developed by NASA Lewis and flown on the Space Electric Rocket Test "SERT-1" spacecraft launched by NASA at its Wallops flight facility in 1964. The SERT-1 flight was followed up by the SERT-2 flight in 1970. Mercury and caesium were preferred propellants for ion engines until Hughes research laboratory performed studies finding xenon gas to be a suitable replacement. Xenon is now the preferred propellant for ion engines as it has a high molecular weight, little or no reactivity due its noble gas nature, and has a high liquid density under mild cryogenic storage.

Experimental mercury vapour turbines were installed to increase the efficiency of fossil-fuel electrical power plants. Mercury was once used as a gun barrel bore cleaner.

HAT MAKING

From the mid-18th to the mid-19th centuries, a process called "carroting" was used in the making of felt hats. Animal skins were rinsed in an orange solution (the term "carroting" arose from this color) of the mercury compound mercuric nitrate, Hg(NO3)2·2H2O. This process separated the fur from the pelt and matted it together. This solution and the vapors it produced were highly toxic. The United States Public Health Service banned the use of mercury in the felt industry in December 1941. The psychological symptoms associated with mercury poisoning are said by some to have inspired the phrase "mad as a hatter". Lewis Carroll's "Mad Hatter" in his book Alice's Adventures in Wonderland was a play on words based on the older phrase, but the character himself does not exhibit symptoms of mercury poisoning.

11

TOXICITY AND SAFETY

Mercury and most of its compounds are extremely toxic and are generally handled with care; in cases of spills involving mercury (such as from certain thermometers or fluorescent light bulbs) specific cleaning procedures are used to avoid toxic exposure. Essentially, it is recommended to physically merge smaller droplets on hard surfaces, combining them into a single larger pool for easier removal by using an eyedropper, or by pushing it into a disposable container. Vacuum cleaners and brooms should not be used because they cause greater dispersal of the mercury. Afterwards, sulfur powder, zinc powder, or some other element that readily forms an amalgam (alloy) with mercury (e.g. finely-divided Cu or Bi) at ordinary temperatures is sprinkled over the area and subsequently collected and properly disposed of. Cleaning porous surfaces and clothing is not effective at removing all traces of mercury and it is therefore advised to discard these kinds of items should they be exposed to a mercury spill.

Mercury can be inhaled and absorbed through the skin and mucous membranes, so containers of mercury are securely sealed to avoid spills and evaporation. Heating of mercury, or compounds of mercury that may decompose when heated, is always carried out with adequate ventilation in order to avoid exposure to mercury vapor. The most toxic forms of mercury are its organic compounds, such as dimethyl mercury and methylmercury. However, inorganic compounds, such as cinnabar are also highly toxic by ingestion or inhalation of the dust. Mercury can cause both chronic and acute poisoning.

OCCUPATIONAL EXPOSURE

Due to the health effects of mercury exposure, industrial and commercial uses are regulated in many countries. The World Health Organization, OSHA, and NIOSH all treat mercury as an occupational hazard, and have established specific occupational exposure limits. Environmental releases and disposal of mercury are regulated in the U.S. primarily by the United States Environmental Protection Agency.

Case control studies have shown effects such as tremors, impaired cognitive skills, and sleep disturbance in workers with chronic exposure to mercury vapor even at low concentrations in the range 0.7–42 μg/m3. A study has shown that acute exposure (4 – 8 hours) to calculated elemental mercury levels of 1.1 to 44 mg/m3 resulted in chest pain, dyspnea, cough, hemoptysis, impairment of pulmonary function, and evidence of interstitial pneumonitis. Acute exposure to mercury vapor has been shown to result in profound central nervous system effects, including psychotic reactions characterized by delirium, hallucinations, and suicidal tendency. Occupational exposure has resulted in broad-ranging functional disturbance, including erethism, irritability, excitability, excessive shyness, and insomnia. With continuing exposure, a fine tremor develops and may escalate to violent muscular spasms. Tremor initially involves the hands and later spreads to the eyelids, lips, and tongue. Long-term, low-level exposure has been associated with more subtle symptoms of erethism, including fatigue, irritability, loss of memory, vivid dreams, and depression.

TREATMENT

Research on the treatment of mercury poisoning is limited. Currently available drugs for acute mercurial poisoning include chelators N-acetyl-D, L-penicillamine (NAP), British Anti-Lewisite (BAL), 2,3-dimercapto-1-propanesulfonic acid (DMPS), and dimercaptosuccinic acid (DMSA). In one small study including 11 construction workers exposed to elemental

12

mercury, patients were treated with DMSA and NAP. Chelation therapy with both drugs resulted in the mobilization of a small fraction of the total estimated body mercury. DMSA was able to increase the excretion of mercury to a greater extent than NAP.

FISH

Fish and shellfish have a natural tendency to concentrate mercury in their bodies, often in the form of methylmercury, a highly toxic organic compound of mercury. Species of fish that are high on the food chain, such as shark, swordfish, king mackerel, albacore tuna, and tilefish contain higher concentrations of mercury than others. As mercury and methylmercury are fat soluble, they primarily accumulate in the viscera, although they are also found throughout the muscle tissue. When this fish is consumed by a predator, the mercury level is accumulated. Since fish are less efficient at depurating than accumulating methylmercury, fish-tissue concentrations increase over time. Thus species that are high on the food chain amass body burdens of mercury that can be ten times higher than the species they consume. This process is called biomagnifications. Mercury poisoning happened this way in Minamata, Japan, now called Minamata disease.

REGULATIONS

In the United States, the Environmental Protection Agency is charged with regulating and managing mercury contamination. Several laws give the EPA this authority, including the Clean Air Act, the Clean Water Act, the Resource Conservation and Recovery Act, and the Safe Drinking Water Act. Additionally, the Mercury-Containing and Rechargeable Battery Management Act, passed in 1996, phases out the use of mercury in batteries, and provides for the efficient and cost-effective disposal of many types of used batteries. North America contributed approximately 11% of the total global anthropogenic mercury emissions in 1995.

In the European Union, the directive on the Restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment (see RoHS) bans mercury from certain electrical and electronic products, and limits the amount of mercury in other products to less than 1000 ppm. There are restrictions for mercury concentration in packaging (the limit is 100 ppm for sum of mercury, lead, hexavalent chromium and cadmium) and batteries (the limit is 5 ppm). In July 2007, the European Union also banned mercury in non-electrical measuring devices, such as thermometers and barometers. The ban applies to new devices only, and contains exemptions for the health care sector and a two year grace period for manufacturers of barometers.

13

Mercury in the Environment

Mercury is a highly toxic element that is found both naturally and as an introduced contaminant in the environment. Although its potential for toxicity in highly contaminated areas such as Minamata Bay, Japan, in the 1950's and 1960's, is well documented, research has shown that mercury can be a threat to the health of people and wildlife in many environments that are not obviously polluted. The risk is determined by the likelihood of exposure, the form of mercury present (some forms are more toxic than others), and the geochemical and ecological factors that influence how mercury moves and changes form in the environment.

Toxic Effects

The toxic effects of mercury depend on its chemical form and the route of exposure. Methylmercury [CH3Hg] is the most toxic form. It affects the immune system, alters genetic and enzyme systems, and damages the nervous system, including coordination and the senses of touch, taste, and sight. Methylmercury is particularly damaging to developing embryos, which are five to ten times more sensitive than adults. Exposure to methylmercury is usually by ingestion, and it is absorbed more readily and excreted more slowly than other forms of mercury. Elemental mercury, Hg(0), the form released from broken thermometers, causes tremors, gingivitis, and excitability when vapors are inhaled over a long period of time. Although it is less toxic than methylmercury, elemental mercury may be found in higher concentrations in environments such as gold mine sites, where it has been used to extract gold. If elemental mercury is ingested, it is absorbed relatively slowly and may pass through the digestive system without causing damage. Ingestion of other common forms of mercury, such as the salt HgCl2, which damages the gastrointestinal tract and causes kidney failure, is unlikely from environmental sources.

Risk to People

People are exposed to methylmercury almost entirely by eating contaminated fish and wildlife that are at the top of aquatic foodchains. The National Research Council, in its 2000 report on the toxicological effects of methylmercury, pointed out that the population at highest risk is the offspring of women who consume large amounts of fish and seafood. The report went on to estimate that more than 60,000 children are born each year at risk for adverse neurodevelopmental effects due to in utero exposure to methylmercury. In its 1997 Mercury Study Report to Congress, the U.S. Environmental Protection Agency concluded that mercury also may pose a risk to some adults and wildlife populations that consume large amounts of fish that is contaminated by mercury.

How can I avoid consuming mercury in fish?

Options for avoiding the mercury in mercury-contaminated fish are more limited than for fish contaminated with PCBs, dioxins and other organic contaminants. Younger fish tend to have lower concentrations of mercury than older, larger fish within the same waterbody. Mercury concentrates in the muscle tissue of fish. So, unlike PCBs, dioxins and other organic contaminants that concentrate in the skin and fat, mercury cannot be filleted or cooked out of consumable game fish.

Risk to Wildlife

14

Fish-eating birds in certain parts of the United States may ingest large amounts of methylmercury in their diet.

In several areas of the United States, concentrations of mercury in fish and wildlife are high enough to be a risk to wildlife. It is difficult to prove cause and effect in field studies, however, because other factors that may contribute to the biological effect under study (for example, reproductive success) are often impossible to control. Scientists have discovered toxic effects in the field at concentrations of mercury that are toxic in the lab, and controlled lab studies have found toxic effects at concentrations that are common in certain environments. In studies in Wisconsin, reductions in loon chick production has been found in lakes where mercury concentrations in eggs exceed concentrations that are toxic in laboratory studies. At dietary mercury concentrations that are typical of parts of the Everglades, the behavior of juvenile great egrets can be affected. Studies with mallards, great egrets, and other aquatic birds have shown that protective enzymes are less effective following exposure to mercury. Analyses of such biochemical indicators indicate that mercury is adversely affecting diving ducks from the San Francisco Bay, herons and egrets from the Carson River, Nevada, and heron embryos from colonies along the Mississippi River. Finally, other contaminants also affect the toxicity of mercury. Methylmercury can be more harmful to bird embryos when selenium, another potentially toxic element, is present in the diet.

Fish Advisories

The steadily increasing number and geographic extent of State advisories against the consumption of fish because of mercury contamination has raised the awareness of the widespread nature of the mercury hazard. Fish consumption advisories for methylmercury now account for more than three-quarters of all fish consumption advisories in the United States. Forty States have issued advisories for methylmercury on selected water-bodies and 13 states have statewide advisories for some or all sportfish from rivers or lakes. Coastal areas along the Gulf of Mexico, Maine, and the Atlantic Ocean from Florida through North Carolina are under advisories for methylmercury for certain fish.

15

Mercury can cause deformities in developing animals.

Mercury concentrations are high enough to trigger fish consumption advisories in many States.

Sources of Mercury

Alkali and metal processing, incineration of coal, and medical and other waste, and mining of gold and mercury contribute greatly to mercury concentrations in some areas, but atmospheric deposition is the dominant source of mercury over most of the landscape. Once in the atmosphere, mercury is widely disseminated and can circulate for years, accounting for its wide-spread distribution. Natural sources of atmospheric mercury include volcanoes, geologic deposits of mercury, and volatilization from the ocean. Although all rocks, sediments, water, and soils naturally contain small but varying amounts of mercury, scientists have found some local mineral occurrences and thermal springs that are naturally high in mercury.

16

What factors affect the methylation?

Methylation is a product of complex processes that move and transform mercury. Atmospheric deposition contains the three principal forms of mercury, although inorganic divalent mercury (HgII) is the dominant form. Once in surface water, mercury enters a complex cycle in which one form can be converted to another. Mercury attached to particles can settle onto the sediments where it can diffuse into the water column, be resuspended, be buried by other

17

sediments, or be methylated. Methylmercury can enter the food chain, or it can be released back to the atmosphere by volatilization.

The concentration of dissolved organic carbon (DOC) and pH have a strong effect on the ultimate fate of mercury in an ecosystem. Studies have shown that for the same species of fish taken from the same region, increasing the acidity of the water (decreasing pH) and/or the DOC content generally results in higher mercury levels in fish, an indicator of greater net methylation. Higher acidity and DOC levels enhance the mobility of mercury in the environment, thus making it more likely to enter the food chain.

Mercury and methylmercury exposure to sunlight (specifically ultra-violet light) has an overall detoxifying effect. Sunlight can break down methylmercury to Hg(II) or Hg(0), which can leave the aquatic environment and reenter the atmosphere as a gas.

 

Environments Where Methylmercury is a Problem

Although mercury is a globally dispersed contaminant, it is not a problem everywhere. Aside from grossly polluted environments, mercury is normally a problem only where the rate of natural formation of methylmercury from inorganic mercury is greater than the reverse reaction. Methylmercury is the only form of mercury that accumulates appreciably in fish. Environments that are known to favor the production of methylmercury include certain types of wetlands, dilute low-pH lakes in Northeast and Northcentral United States, parts of the Florida Everglades, newly flooded reservoirs, and coastal wetlands, particularly along the Gulf of Mexico, Atlantic Ocean, and San Francisco Bay.

How does mercury enter the food chain?

The exact mechanisms by which mercury enters the food chain remain largely unknown and may vary among ecosystems. Certain bacteria play an important early role. Bacteria that process sulfate (SO4=) in the environment take up mercury in its inorganic form and convert it to methylmercury through metabolic processes. The conversion of inorganic mercury to methylmercury is important because its toxicity is greater and

18

Sampling mercury in water requires extra care to avoid cross contamination because concentrations in water are so low.

because organisms require considerably longer to eliminate methylmercury. These methylmercury-containing bacteria may be consumed by the next higher level in the food chain, or the bacteria may excrete the methylmercury to the water where it can quickly adsorb to plankton, which are also consumed by the next level in the food chain. Because animals accumulate methylmercury faster than they eliminate it, animals consume higher concentrations of mercury at each successive level of the food chain. Small environmental concentrations of methy-lmercury can thus readily accumulate to potentially harmful concentrations in fish, fish-eating wildlife and people. Even at very low atmospheric deposition rates in locations remote from point sources, mercury biomagnification can result in toxic effects in consumers at the top of these aquatic food chains.

Mercury Contamination - Past, Present, and Future

In highly polluted areas where mercury has accumulated through industrial or mining activities, natural processes may bury, dilute, or erode the mercury deposits, resulting in declines in concentration. In many relatively pristine areas, however, mercury concentrations have actually increased because atmospheric deposition has increased. For instance, concentrations of mercury in feathers of fish-eating seabirds from the northeastern Atlantic Ocean have steadily increased for more than a century. In North American sediment cores, sediments deposited since industrialization have mercury concentrations about 3-5 times those found in older sediments. Some sites may have become methylmercury hot spots inadvertently through human activities. Lake acidification, addition of substances like sulfur that stimulate methylation, and mobilization of mercury in soils in newly flooded reservoirs or constructed wetlands have been shown to increase the likelihood that mercury will become a problem in fish. Although scientists from USGS and elsewhere are beginning to unravel the complex interactions between mercury and the environment, a lack of information on the sources, behavior, and effects of mercury in the environment has impeded identification of effective management responses to the Nation's growing mercury problem.

Guidance and Awareness Raising Materials under new UNEP Mercury Programs

19

Loons are especially vulnerable to methyl-mercury because a high percentage of their diet is fish.

(Indian Scenario)

Guidance material

Mercury distribution in the environment has been a focus of scientific attention because of the potential health risks posed by mercury exposure. Never before in the history of mankind has there been such a vast multiplicity of environmental risk factors, nor there has been such an expression of concern regarding inherent danger of mercury and its likely impact on diverse aspects on human health. Further organic mercury, mostly methyl mercury (MeHg) the most toxic species is bio accumulating in the biota and subsequently biomagnified in the aquatic food chain, especially in fish. Given the human health concern, it is critical and important that awareness programme is launched to educate the populations to the risk and impact of mercury exposure in humans especially potentially vulnerable population viz pregnant women, breast feeding women, the foetus new born and young children residing in the hot spot area’s of the country and also consequences of MeHg exposure through fish consumption.

There is a strong cultural pattern of fish consumption among coastal people (East, West and Southern coast of India) and among population residing in the plains around industrial sites. Therefore, their fish consumption pattern must be understood when their mercury exposure through fish consumption is to be evaluated. Certain species of fish are considered safe for consumption. Therefore it is important to account for the factors that may affect mercury exposure.

Based on the important research findings and key policy development having occurred over past few years there is sufficient evidence of significant global adverse impacts of mercury and its compounds to warrant national and international action to reduce the risk to human health and the environment. A consensus has emerged among national and international authorities to lower the

the limits of MeHg exposure and / or stronger warning to help sensitive populations to avoid exposure, particularly for pregnant women, breast-feeding women, women who intent to become pregnant and children. These plans are being developed to raise national awareness of the critical need to sharply reduce human exposure to mercury.

Although it is well recognized that mercury is wide spread in the Indian environment and that exposure occurs primarily through consumption of fish, information about its distribution in blood system and hair mercury levels in general Indian population is lacking. Hence it has become difficult to fully evaluate the public health significance of mercury problem. Recent evidence has come to light that exposure to mercury is widespread and occurring at levels exceeding health based recommended value among Indian Population. Exposure information of women for childbearing age has also become urgently needed, since fetal exposure is known to be a critical window of exposure to the compound. Further the factors that may affect infant mercury levels due to in utero and / or lactation exposure is lacking. For such data analysis, mothers and their respective infants from the hot spots need to be interviewed (birth history) and biological samples (maternal and infant hair, and breast milk) need to be collected and analyzed. Mercury concentration in breast milk reflects mercury concentration in blood. In the hair, once mercury is bound, it remains there. Mercury concentration in breast milk therefore reflects most recent exposure, where as mercury concentration in hair is related to long term exposure.

20

In addition, questions have to be addressed to resolve the confounding factors that could affect mercury exposure and neurodevelopment outcome and cardiovascular disease in Indian population co-exposed to pesticides. WHO estimates that incidence of pesticide poisoning has doubled during the past ten years. It is alarming that developed countries accounted for only 15% of the worldwide use of pesticides. However over 50% of pesticides poisoning occurred in developing countries and mainly due to easier availability, misuse and

improper handling mainly because of lack of awareness. Interestingly no information is available on its role on the mercury exposure and its correlation with neurodevelopment changes. Other major confounding factors that may affect mercury absorption/accumulation in Indian context are infections and protein calorie malnutrition.

Several studies have shown that pesticide exposure in Indian population is much higher compared to Western World. In India pesticides (both organochlorine and organophosphates) are extensively used in spite of their restrictions. In a most recent study from the two cities of India (Bhopal and Lucknow) it was revealed that through breast milk infants consumed 8.6 times more of endosulfan and 4.1 times HCH more than the average daily intake (ADI) levels recommended by WHO. Among the various pesticides present in the breast milk, endosulfan concentration (0.363 ± 0.077 mg/lt.) exceeded HCH concentration by 3.5 fold, chloropyrifos by 1.5 folds and malathion by 8.4 folds. The high levels of pesticides in the breast milk is a reflection of consumption of food, drink, vegetables, fish etc. containing excessive levels of these pesticides (Human and Expt. Toxicol. 21, 1-6, 2002 and 22, 73-76, 2003). In another recent study it was estimated that 0.619 mg of endosulfan is the ADI per capita by humans through fish (Int. J. Ecol. Environ. Sci. 27, 117 – 120, 2001). Out of 422 vegetables samples tested, 79% were contaminated with endsoulfan, with 14% showing above MRL (All India Coordinated Res. Project on Pesticide Residue, pp 178, 1999). It is unfortunate that pesticide contamination has been detected even in bottled water and soft drink several fold higher than EC and American norms. (Press Release; Times of India, Feb 4, 2003 and Aug 6, 2003). As a result, Bureau of Indian Standard (BIS) equivalent to EPA, adopted strict EC norms of pesticides levels in water (0.0001 mg/lit for individual of pesticides levels in 0.0005 mg/lit, the limit of total pesticide residue). It is expected that new levels would be effective from January 2004. These informations may help to take action to reduce mercury as well as pesticide exposure, develop awareness of mercury and pesticide exposure, management of mercury exposure and to develop advisories to prevent exposure to critical doses of mercury and pesticides during awareness programme as per recommendations of the UNEP, Governing Council Meeting held in Nairobi, Kenya, in Feb. 2003.

The first phase of awareness programme would be four days Brain Storming Session on “Nature and Magnitude of Mercury Problem in India” around March 2004 with the objectives of (i) Projecting the nature and magnitude of the mercury problem in India (ii) Tools and strategies to mitigate mercury pollution that has an impact on human health and environment and (iii) To suggest immediate and long term national action as appropriate to reduce man made mercury release. (iv) To develop information network to communicate to public the risk and impact of mercury exposure in humans especially vulnerable population and (v) To adopt policies to prevent illegal trafficking of mercury. The invitees would include representatives from Government (Min. of Environment and Min. of Health), Member of Industries, Non-Government Organizations, WHO, World Bank, UNEP, etc.

Subsequently, we would develop training materials, guidance document and tool kit on the following topics to organize regional / sub – regional awareness raising workshop sometimes

21

in July 2004 at various hot spots in India in promoting measures to reduce man made mercury release that have adverse impact on human health and environment:

1. Nature and Magnitude of the Mercury problem in India.

2. Identifying and evaluation of populations at risk.

3. Risk communication and outreach to populations at risk

4. Developing inventories of mercury uses and release

5. Potential pollution prevention measures, control technologies and strategies for reducing mercury uses and releases.

6. Increasing awareness and promotion of mercury free products, technologies and processes, or responsible use of mercury, where appropriate.

7. Deleterious impact on human health and the environment attributed to mercury and its global capacity for transport and cycling

8. Initiative to protect human health and environment through measures that will reduce or eliminate release of mercury and its compounds to the environment and establishing national implementation programme.

Awareness Raising Materials Under the New UNEP Mercury Programme

India May Become ‘Hot Spot for Mercury Poisoning

Asia is the biggest villain in polluting the atmosphere with new mercury emissions, impacting the health of people as well as wildlife, a new UN report says. In even worse news for India, the first global study on this hazardous heavy metal says Indian could be one of a dozen hot spots after an upsurge in gold-mining over three decades.

Source : Chandrika Mago, Times of India, February 4, 2003

India’s population was unaware of mercury hazards for last few dacades. Due to global scenario, the awareness regarding hazards caused by mercury pollution is increasing among Indians. Chloralkali industries are still the major source of mercury release in atmosphere and surface water. Other industries, which contributes to mercury pollution in India, are Coal fired plants viz. thermal power plants, steel industries and cement plants. Plastic industry (mercury is used as a catalyst), pulp and paper industry, medical instruments and electrical appliances, certain pharmaceutical and agricultural product accounting for additional consumption of mercury. India consumes 75 million tones of coal every year in various thermal power plants. Coal contains mercury and its combustion as a source of energy is often sited as significant source of mercury emission. Mercury levels are reported to be extremely high in the working environment of these industrial processes including thermometer factories, and even medical practices such as dental clinics. The effect of mercury on human health and the working environment in the industry has not been taken seriously by Management. The hazardous working conditions and dangerous waste management practice is still continuing in several industries related to mercury (Figure 1).

22

The document enumerates the enormity of mercury problem in India as compared to Global scenario, and its amelioration by using various technologies and regulations. The major points addressed are:

1. National threat Vs local concern

2. Main contributors to mercury emissions in India

3. Mercury free alternatives

4. Mercury laws

5. Technologies and practices

6. Strategies to reduce mercury exposures

National Threat versus Local Concern

(Human & Environment)

23

• Mercury contamination in water in India is verging on alarming situation due to discharge of industrial effluents containing mercury ranging from (0.058-0.268 mg/l) against 0.001mg/l. as per WHO and Indian standards.

• About 0.20 kg of mercury is lost per ton of caustic produced thereby creating serious pollution causing adverse effect to biological system.

• Mercury levels in water near caustic chlorine industry has been reported as high as 0.176 ± 0.0003 mg/l. in water and 596.67 ± 25.17 mg/kg dry wt. soil against the prescribed limit of 0.001 mg/l. in water and 0.05 mg/kg in soil.

• Environmental Mercury concentration in Chambur, Mumbai is almost three times higher during the dust storm when compared to normal conditions of 0.93 ± 0.66 mg cm3. Most Hg was present in gaseous form. In certain areas the average precipitation of Hg was 82 μg/l.

• The iron and steel industry, the single largest source of huge quantities of particulates was reported to contain as high as 56 ppm Hg in dust fall out and 40-72 ppm in surface soils

• The fallout of elemental mercury over the soil-horizon in the vicinity of a steel plant was reported to be in the range of 60.36 to 836.18 g/km2/month

• High concentration of the gaseous mercury present in the ambient air closer to the chloroalkali industries may lead to long-range transport of mercury.

• The concentration of mercury in blood and hair of human population has been reported as high as 100 μg/dl and 8 μg/g respectively at industrial site compared to 5 μg/dl. and 1 μg/g, respectively in unexposed population.

• Based on the studies of occupationally exposed Indian adult population several fold higher concentration of mercury in blood (5 μg/dl.) and hair (0.15 – 8.4 μg/g) was observed compared to control population.

• The occurrence of mercury in bronchial wash out of plant workers from coal-fired industries was 20 – 85.2 μg, 16 – 56 μg, 10 – 17.5 μg/ml from Steel industry, Thermal power industry and Cement industry, respectively.

• The concentration of mercury in fish in other sea food consumed in certain coastal areas reported in range of 0.03-10.82 μg/g compared to the permissible limit of 0.5 μg/g.

There is a potential risk to human health and environment due to the entry of mercury in food chain in and around chloralkali plant. The basket fruits and vegetables contain several folds higher concentration mercury in certain industrial area against prescribed Indian standards.

MERCURY SPILL

• The most lethal fallout from the September 15,earthquake that rocked the Andaman archipelago has been a 50 kilogram leakage of lethal mercury from east island lighthouse in North Andaman. This spill is posing a health hazards to the local people as well as to the fragile ecology of the entire region. Environmental organizations have expressed apprehension over the resultant toxicity that can threaten the flora and fauna and the amount of mercury that enter the food chain.

24

• Regular monitoring of mercury pollution located in the eastern part of the country revealed that the different vegetables grown in the contaminated kitchen garden, particularly the leafy vegetables were found to be bio-concentrate mercury at statistically significant level. High concentration of mercury was also found in wheat and rice and leafy vegetables grown in the southern part of the India.

• Aquatic and terrestrial plants including a few vegetables and crops growing in heavily mercury contaminated soil in and around chloralkali plant at Ganjam,east coast revealed a significant correlation between soil and plant mercury level.

• Similar situation is reported for the high concentration of total mercury and methyl mercury in marine food in Thane creek, west coast. The methyl mercury concentration ranges from 20.4 to 344.4 ng/g dry weight and maximum concentration has been found in crabs and prawns. The overall total mercury concentration ranged from 62.5 to 548 ng/gm (189 ng/gm). Daily intake of total mercury and methyl mercury from sea food by Mumbai population is estimated at 0.8 μg/g and 0.5 μg/g (1997).

• Baseline study of the level of concentration of mercury in the food fishes of bay of Bengal, Arabian Sea and Indian Ocean reports reveals that mercury levels in 18 groups of fish and other sea food had the mean average values ranged from 5-65 microgram/kg. Levels of the mercury concentration in some known food fish of the Indian Ocean, Bay of Bengal and Arabian Sea were compared with similar species found in the Mediterranean, Atlantic and Pacific Ocean(1979).

• Large numbers of cases had reported during last ten years regarding metals pollution especially mercury in fishes and through them to human beings. High concentrations of mercury in the environment were observed in vicinity of caustic soda plant, indicating high mercury contamination. The total mercury concentration in the fish sample from a contaminated stream from the above sight exceeded the safe limit of 0.5 μg/g wet weight. The environment impact of chloralkali industries in river basin in eastern India has also led to tremendous releases of mercury 60-320 times beyond the permissible limit(0.01mg/kg) in the river bodies. Mercury emissions from massive coal consumption also enhances the level of mercury more than 1 ppm in soil and more than 10 ppb in ground water and ponds.

Risk due to Mercury Amalgam dental fillings

• Mercury amalgam in dental filling poses a real threat of chronic mercury poisoning.

• Blood mercury levels have reported as high as 20 μg/dl. in humans with dental amalgam filling.

• The alternatives are not yet deemed fully capable of substituting amalgam in all types of dental filling.

• Lack of awareness of health hazards of mercury amalgam dental fillings in pregnant women and their precautionary measures.

• The base silver alloy is mostly imported from USA, Switzerland, France, UK and Australia and is cheaper compared to other permanent restorative materials.

Global Threat versus National Concern

• Import of mercury is legal under Indian law. However, it is a proven environmental toxin.

25

• India bound mercury shipment causing a concern to environment, health and security of Urban and Rural Population.

• It is possible to manage and use mercury safely in the developed countries to safe guard the public and environment, but least of all in developing countries lacking in regulatory infrastructure and resources.

• India advocates to World Bank for installation of safe waste disposal technologies for medical waste.

• Scientists in a US estimated that 30 – 70% of Mercury deposition comes from long-range environmental transport of mercury emissions from other countries causing increase concentration in water and biota specially fishes.

Mercury Pollution: Indian ScenarioDrinking water standards for mercury

26

The Bureau of Indian Standards (BIS) has laid down safety limits for drinking water at 0.001 mg of mercury per litre. A number of samples of groundwater in some industrial belts have shown concentrations of mercury higher than safe standards. A study shows levels of mercury to be very high as compared to the permissible limit. The table above shows the critical geographical areas.

Increase in mercury pollution in India

In India, some of the major rivers tested for heavy metals by the Industrial Toxicological Research Centre (ITRC), Lucknow, were found to contain mercury in alarming levels. Testing of seawater by the National Institute of Oceanography, Goa, found increased mercury concentrations in the Arabian Sea. Several studies on fish and prawns in Mumbai, Kolkata, Orissa, etc, have reported alarming rates of mercury concentrations. Recent studies have shown that the total mercury pollution potential from coal in India is estimated to be 77.91 tonnes per annum, if average concentration of mercury in coal is assumed to be 0.272 ppm. About 59.29 tonnes of mercury per annum is mobilised from coalfired thermal power plants alone. The five super thermal power plants in the Singrauli area, which supply 10 per cent of India’s power, are responsible for 16.85 per cent or 10 tonnes per annum of total mercury pollution through power generation.

 The Paryavaran Suraksha Samiti (PSS) collected samples from over 20 villages affected by industrial pollution in the Golden Corridor of Gujarat to investigate the water situation there. The samples were analysed for Mercury and Chemical Oxygen Demand (COD). In Haria village and Atul Complex, mercury was shockingly high at 12 ppm – 1200 per cent more than the permissible limit of 1 ppm. Another sample in Ankleshwar showed mercury at a high level of 2 ppm which is 200 per cent above the standard. Samples in Vadodara-Nandesari ECP Area also showed high mercury levels at 6 ppm and 1.3 ppm, which are 600 per cent and 30 per cent more than the prescribed standards, respectively.

 The People’s Science Institute (PSI) in Dehradun has recently found high levels of mercury in the groundwater sources of Bhopal, especially near the Union Carbide factory. The water is dangerous for human consumption as the area of groundwater contamination is increasing. Water samples from various localities taken for testing showed that contamination levels in some places were as high as 2 ppm. A recent study conducted by the Environmental Science Department of the Guru Gobind Singh Indraprastha University, Delhi, reveals that the concentration of contaminants like arsenic, mercury, nitrates, etc, in the groundwater of Delhi exceeds the permissible limits. The study entailed 50 samples of groundwater being lifted from random spots along a 22-km stretch between Palla and Okhla. The mercury concentration in some samples was as high as 4.6 ppm, 460 per cent above the permissible limit. This alarming presence of mercury in groundwater can be traced to the continuous discharge of sewage and industrial effluents into the Yamuna and, subsequently, into the groundwater aquifer which, being sandy in nature, allows mercury pollution to spread at a rapid rate.

Bibliography Clarkson, T.W., 1997. The toxicology of mercury. Critical Reviews of Toxicology 34, 369–

403.

27

Conti, M.E., Cecchetti, G., 2001. Biological monitoring: lichens as bioindicators of air pollution assessment—a review. Environmental Pollution 114, 471–492.

Ebadian, M.A., Marshell, A., Yong, C., 2001. Mercury Contaminated Material Decontamination Methods: Investigation and Assessment. Hemispheric Centre for Environmental Technology, Florida International University, Miami. HCET-2000-D053-002-04.

Horvat, M., Jeran, Z., Spiric, Z., Jacimovic, R., Miklavcic, V., 2000. Mercury and other elements in lichens near the INA Naftaplin gas treatment plant, Molve, Crotia. Journal of Environmental Monitoring 2, 139–144.

Merian, E., 1991. Metals and their Compounds in the Environment. Occurrence, Analysis and Biological Relevance. VCH publisher.

Ruhling, A., Tyler, G., 1968. An ecological approach to the lead problem. Botaniska Notiser 121, 321–342.

Sanchez Uria, J.E., Sanz-Medel, A., 1998. Inorganic and methyl mercury speciation in environmental samples. Talanta 47, 509–524.

Susana, R., Bendicho, C., 1999. Ultrasound-assisted extraction for mercury speciation by the flow injection-cold vapour technique.

Journal of Analytical Atomic Spectrometry 14, 263–268. 1. US DHHS, Report, Agency for Toxic

Substances and Disease Registry, Atlanta, GA, 1994, TP 93/10.

Nielsen, J. B., J. Toxicol. Environ. Health,1992, 37, 85–122.

Laws, E. A., Aquatic Pollution: An Introductory Text, John Wiley, New York, 2000, 3rd edn, p. 662.

Anon., Down to Earth, 2003, 12, 63–78.

Raj, S. P., Pollut. Res., 1986, 5, 39–43.

Anon., Sixth Annual Progress Report (July 1991–June 1992), Industrial Toxicology

Research Centre, Lucknow, 1992, p. 123.

Govind swamy, C., Roy Viji, A. G. And Jayapaul, A., Int. J. Ecol. Environ. Sci., 1998, 24, 141–146.

Tiwari, R. K. and Dhar, B. B., Mine, Water Environ., 1994, 13, 1–10. Mishra, V., Curr. Sci., 2005, 89, 755– 763.

Anon., Report, Central Pollution Control Board, Delhi, 2000, p. 318.

28