Mercury Poisoning

“Mercury can be ingested, inhaled or absorbed through the skin. Most exposures are from eating fish, amalgam based dental fillings, or exposure at workplaces.” R. R. NAIR



Mercury is a heavy metal and is commonly known as quick silver.

Mercury and its compounds are used in thousands of products. It is dangerous to the flora and fauna even in small doses. In human beings, continuous exposure to mercury leads to damage or impairment to various organs in particular, the brain, the liver and the kidneys.

This article will deal with various aspects of mercury poisoning. For the preparation of this article, many documents such as books, codes, standards and case studies of  eminent researchers are referred, however, due to limitation of space, the list of these references are not included in this article.


The story of mercury begins some 4.5 billion years ago when earth was formed.  At some prehistoric time a man was attracted by a red rock which is known as Cinnabar – the sulphide ore of mercury. He picked the red rock and mixed a bit of it with water and found that it could be used to draw sketches on the walls of caves.  Archaeologists have found that it was used as a pigment in the ruins of ancient Egypt and Babylon and at Mohenjo Daro in Pakistan.

The first recorded mention of mercury was by Aristotle in the 4th century BC and he called it ‘liquid silver’. Five centuries late the Greek physician Pedanius Dioscorides and Pliny used mercury as medical ointment.

The introduction of mercury into scientific research occurred in 1643 with the invention of barometer by Torricelli, who used mercury to determine the pressure of the atmosphere.  In 1720 Fahrenheit invented the mercury thermometer. Joseph Priestley (1733-1804) initiated another important scientific use of mercury by sealing of water soluble gases in gas analyses. In 1799 Howard prepared mercury fulminate which was used as a detonator for explosives and which had played an important role in peace and war in the history of nations.

The name ‘Mercury’ was given by Alchemists after the fleet-footed Greek God. The symbol Hg (Hydrargyrum) is assigned by Pliny.


Mercury is made from Cinnabar. The rock Cinnabar is crushed by giant machines and then roasted in oil-fired furnaces at nearly 1080 O F.  The mercury is released as vapour.  The vapour is piped into condensers after condensation it eventually emerged as Mercury.

The Mercury bearing Cinnabar is mined in Spain, USSR, Japan, Yugoslavia, Africa, South America, British Columbia, Mexico, Czechoslovakia, Manila, USA, etc.

The production of mercury in Almaden mine in Spain began about 700 BC. The Idria mine in Yugoslavia began production in 1470 and has the world’s largest production record next to Almaden mine. The Santa Barbara mine in Peru began production in 1566, The Monte Amiata mine in Rome began production around 1868. The production of Mercury in the United States began in California about 1850.

According to Lars D. Hylander and Markus Meilib, the World production of Mercury for a period of 500 years (from 1501-2000) was 9,22,812 metric tons. About 33% of production of Mercury was shared by Spain, North America, Slovenia, Italy. Former USSR shared 14.9%, 11.6%, 11.3% and 8.4% respectively. The remaining 20.8% was shared by China, Mexico, Africa and other countries.

The total global production of primary Mercury has been approximately 2000 tons annually in recent years. This is a dramatic decline since World War II and the 1960s and 1970s, when production peaked at approximately 10,000 tons per year, mainly because of intense industrial use. Besides Almaden, the most important mercury mine in the world is currently the Khaydarkan mining complex in Kyrgyzstan.


Mercury (Hg) is a silvery-white metal with a bluish tinge. Mercury is the only pure metal which is liquid at ordinary temperature. It boils at 356.85 O C. It melts at –38.87 O C.  Its metallic character was accepted only in 1759.  It has a slight vapour pressure even at ordinary temperatures and the vapour pressure is such that, if sufficient of the liquid is exposed in a closed room at normal temperatures the concentration of mercury vapour in the air may rise to more than 100 times the threshold limit value.  It has a vapour pressure of 0.012 mm Hg at 20 O C and 1 mm Hg at 126 O C.  It does not dissolve in dilute hydrochloric and sulphuric acid, but it dissolves in dilute nitric acid and hot concentrated sulphuric acid.  It is insoluble in water and organic solvents.


Mercury as an element has about 3000 uses today. The forms of mercury in use can be classified in three categories viz. (1) Metallic Mercury, (2) Organic Mercury Compounds and (3) Inorganic Mercury Compounds. Some of the individual uses of mercury and its compounds are listed in the following paragraphs.

5.1   Metallic Mercury:
Metallic mercury is used in the manufacture of barometers, pressure sensory devices, gauges, valves, pump seals, etc.  It is also used in the manufacture of electric bulbs, mercury vapour tubes, radio valves, X-Ray tubes, switches, batteries, rectifier, etc. It is used as an amalgam with silver, brass and tin plating.  Dentists use as an amalgam for filling the teeth cavities.  In the chemical industry, it is used as a catalyst for the production of chlorine and caustic soda and alkalines of acetic acid and acetaldehyde from acetylene.  It is also used in laboratories.

5.2 Organic Mercury Compounds:
According to one reliable estimate more than 400 phenyl mercurials and at least that number of alkyl mercury compounds have been synthesised.

In addition to these two large groups, mercury derivatives have been obtained from a wide range of organic compounds. The most important one in common use are the alkyls and the aromatic hydrocarbons or aryls.

In the alkyl group ethyl mercuric chloride is used as fungicide for seed or bulb treatment.  Ethyl mercuric phosphate is used as a seed fungicide and timber preservative.

N (ethyl mercuric)-p-toluene sulphonamide is used in the treatment of seeds and bulbs for seed-borne disease and fungi. Methyl­mercury dicyanidamide is used as a disinfectant and as a fungicide for treating seeds.

Phenylmercury urea is used as a disinfectant and fungicide for seed treatment. Hydroxymercuric chlorophenol is also used as a seed disinfectant and fungicide. Phenylmercuric acetate is used as an antiseptic fungicide, herbicide and as a preservative for paints. Phenylmercuric nitrate is used as an antiseptic germicide, fungicide, preservative. Phenylmercuric oleate is used as a mildew-proofing agent for paints. It acts as fungicide anti germicide also. Phenylmercuric propionate is used as a fungicide and bactericide for paints and industrial finishes. Phenylmercuric benzate is used as a bactericide and fungicide and as a denaturant for alcohol.

5.3 Inorganic Mercury Compounds:
Inorganic mercury compounds include mercuric cyanide, mercuric oxycyanide, mercuric potassium cyanide, mercuric and mercurous phosphate, mercury thallium, mercuric iodide, mercurous nitrate and mercuric thiocyanate. These substances are all highly poisonous and some such as, mercuric oxycyanate, mercurous nitrate and mercurous chlorate constitute a considerable fire hazard.

Mercuric oxide is used in the paint and colour industry for the manufacture of pigments and antifouling marine paints. Mercuric sulphide is used in the paint and colour industry for the manufacture of vermilion. Mercuric chloride or mercuric cyanide is used as components of solution for sterilization of instruments etc. in hospitals.

Ammoniated mercury, yellow mercuric oxide or prime virgin mercury, blue ointment, etc., are used in a variety of therapeutic and cosmetic skin creams for various skin ointments.

In timber industry mercuric chloride is used for timber preservation and in photography as an intensifying agent for photographic images. The mercuric cyanide is used in the manufacture of cyanogen gas. The mercuric sulphate is used in the extraction of gold and silver from roasted Pyrites.


Mercury poisoning may occur through (1) Ingestion of organic and inorganic compounds of mercury (2) Inhalation of dust, fumes and mists of mercury and its compounds (3) Skin & Eye contact with mercury and its compounds.

6.1 Ingestion:
Ingestion of organic & inorganic compounds of mercury by man might occur through the consumption of mercury contaminated water, food and suicidal attempt to consume the compound itself.

The open sea water contain mercury. The presence of mercury in sea water was demonstrated by Joseph Louis Proust in 1799 and subsequent studies have found one or another form of mercury in all types of soils and in all kinds of foods. Alfred Stock in 1934 and 1938 found mercury present in the North Sea and several sources of fresh water. The highest value 0.48 parts per million was in rain water. According to Goldberg, annual erosion and weathering are estimated to contribute some 5000 tons to the sea and another 4000-5000 tons of mined mercury are lost to sea, soil and the atmosphere. The presence of mercury in sea water may not affect directly the man. But the presence of mercury in the water – canal, river, lake, might affect the man as the water is used for drinking. The amount of mercury added to the drinking water as a result of treatment with chlorine and another chemicals are unknown.

According to the estimate of Food & Agriculture Organisation of  USA, mercury concentration in surface sea water are about 0.1 µg/L The United States Study Group on Mercury Hazards 1971, estimated that the mercury concentration in rain water as 0.5 µg/L. The Committee on International Standards for Drinking Water, estimates the concentration in surface water generally below 1 µg/L. An average man takes 2.5 litres of water per day. Based on this, the World Health Organisation (WHO) has recommended that the tentative upper limit of mercury in drinking water should be 1 µg per litre i.e., the upper limit of mercury intake through the water would be 2.5 µg per person per day mainly in the form of inorganic mercury.

Food articles like fish, meat, chicken, grain, etc., can be contaminated with mercury. Since mercury and its various compounds are used in various industrial and agricultural productions, food articles are likely to be contaminated by mercury. The consumption of mercury contaminated grams, meat, etc., are only accidental. But the consumption of mercury contaminated fish is likely and most likely amongst the regular fish eaters. The mercury contained in the fish are in the form of methyl mercury – a highly toxic organic compound. Until 1967 the whole world was puzzled about the presence of methyl mercury in the fish. In 1967 two Swedish scientists Soren Jensen and Arne Jernelov found that the microorganism convert elemental mercury and its compounds into methyl mercury.

In 1971 the United States Food and Drugs Administration conducted a nationwide survey and found less than 3% of 1400 random samples of market fish in the USA contain mercury in excess of 500 µg/Kg. According to a WHO estimate some 99% of the world commercial catch has a total mercury content not exceeding 50 µg/Kg and 95 % probably contain less than 300 µg/Kg. As per the report of working party on the monitoring of food stuffs for mercury and other heavy metals, the total content of total diet samples examined in the United Kingdom, contain generally below 5 µg/Kg in fish, however values up to 200 µg/Kg were found. According to estimate by Smart N.A., the samples of Japanese rice have been found to contain as much as 200-1000 µg of mercury per kilogram. Swedish chicken eggs examined in 1966 contained about 0.02 µg of mercury per gram of egg white. Stock A. and others have found higher concentration of mercury in meat and butter than in fish.

Few case histories of mercury poisoning occurred through food chain are given below:

Fish: The first notice of mercury’s high cost to the human environment was received by man in 1953. In 1953, villages around Minamata, a small city of Japan, fishermen and their families began to fall victim to a mysterious disease which was initially, called as Minamata Disease. Some 202 people were affected by this disease within the next few years. Amongst the affected, 52 died. Most of the victims had eaten the fish three times a day. When the first victims reported in 1953, local doctors made various diagnosis such as brain tumour, syphilis etc. Since the number of patients were increasing by year by year, the local doctors called for help from the Kumamoto University School of Medicine. Dr. Tadeo Takeuchi, a pathologist of the University investigated the case. He tried to find out the cause for this. It took few years to establish the real cause of the epidemic. In this process, an artificial ‘Minamata Disease’ was created by feeding fish from the bay to fish eating animals like cats, dogs, etc. From these, investigations it was found that those who ate fish from the bay were affected by the disease. Further studies revealed that the methyl mercury contaminated fish were the cause for the epidemic. Then search went on to find out the source of methyl mercury in fish. Later on it was found that a firm known as Chisso Corporation, manufacturing chemical fertilizer, industrial chemicals, plastic materials and synthetic fibres, was responsible for throwing the mercury into the bay of Minamata. The firm was manufacturing acetaldehyde and vinyl chloride used in the plastic industry. In both the cases mercury compounds serve as catalysts. During the process of manufacture some mercury used to escape into the bay along with other industrial waste. Micro- organism in the bay converted the, mercury compound into methyl mercury form. The fish in the bay absorbed it through their gills. According to the Study Group on Minamata Disease, the methyl mercury, was present in water at an undetectably low level, but was taken by fish and shellfish biologically concentrated. In some instances the concentration of mercury, as total mercury, in fish and shellfish exceeded 1000 µg/Kg.

According to Dr. Donald Hunter, Minamata disease was again reported in 1964-65 in the area of Agano River, Niigata Prefecture, Japan. This time 49 persons were affected of whom, 6 died.

The presence of mercury in fish has also been recognised in studies in the Nordic countries, in Canada and in U.S.A. Mercury is probably present in fish in other industrial countries too.

According to WHO, mercury, when present in fish cannot be removed by cooking or processing and appears to be firmly bound as methyl mercury to the sulfhydryl group of proteins. Possibly only with this in view the Canadian health authorities burned one million pounds of fish, when they found high concentration of mercury in fish.

Meat: In 1970, a labourer in New Mexico obtained waste grain seed treated with methyl mercury compound for feeding his hogs. The seed bag constrained a warning label that the seeds are poisonous to animals and human. But the Mexican ignored the warning and fed the grain seed to his hogs for some time. Later on, he butchered one and he and his family ate the meat almost daily for three months. As a result, three of his children were severely crippled. A fourth child poisoned in his mother’s womb, was born blind and retarded.

Grains: Smart N.A. estimates the use of mercury pesticides in the world amounts to about 2000 metric tons a year. Inorganic and organic mercury compounds have been used to treat seed potatoes, flower bulbs, and especially grain seed like wheat, rice, barley, oats etc. Several outbreaks of poisoning have been described as a consequence of such use of mercury compounds and two such cases are narrated below:

Wheat: In 1956 and 1960 peasants in Iraq obtained seed wheat dressed with ethyl mercury para-toluene sulphonanilide for the preparation of homemade bread and this resulted in mass poisoning of peasants and their families. In 1972 also the villagers in Iraq obtained-grain seed treated with methyl mercury for making homemade bread. The villagers ate the homemade bread for some time. As a result some 450 people died and thousands more afflicted.

Maize: In 15th May, 1971, four children were seriously ill with gastroenteritis in Yalovi, a village in the Volta region of Southern Ghana. They were brought to hospital for treatment. But all died immediately after admission. The doctors attending on the cases diagnosed the probable cause as gastrointestinal tract of anthrax. By 18th May, twenty people died out of 144 reported sick. Eight domestic cats and four dogs also died during the period. But the veterinary doctor’s report showed that the deaths were not due to anthrax. Investigation further continued and later on it was found that eating of maize treated with pesticides as the reason for the outbreak of food poisoning. The seed maize was dressed with methoxyethyl mercuric acetate, a fungicide in the form of a grey powder and stored away ready for sowing. The villagers obtained the maize at cheap price ad first washed thoroughly with warm water to remove the pesticides. Then it was boiled, salted and eaten. The poisoned maize was eaten for about two weeks. Out of the 144 reported sick, 20 died and 12 were ill enough to prolonged treatment. Both sexes and all ages were affected but children were severely affected than adults.

There were also similar cases reported in Guatemala and Pakistan.

6.2 Inhalation:
Inhalation of dust, fumes and moisture of mercury is another source of absorption of mercury by man. The general atmosphere contain very small particle of mercury which gets into human system in the normal way of breathe. A part from this man made pollution, contribute mercury into air, which gets into the human system through the normal breathe.

According to recent data, coal burning may be the largest single source of mercury in the environment. A typical 700 MW coal burning plant often emits as much as 90% mercury present in the fuel. This is by no means a small quantity, a single plant alone has been found to emit 1500 pounds of mercury annually in vaporized form. Averages of 1000 pounds per year have been found in studies of eight Illinois power plants.

Exposure of vapour from metallic mercury and mercuric compounds, which are used in various industrial operations, is another source of intake of mercury by workers engaged in the plants. The atmosphere of plants manufacturing, processing mercury and its compounds, without proper ventilation control, can contain mercury vapour. The workers in and around this atmosphere inhale the air which contain higher concentration of mercury vapour.

6.3 Skin & Eye Contact:
Mercury and its compounds are skin irritants. According to American Industrial Hygiene Association (AIHA), a little solution of one part of salt in 4000 parts of water can be very irritating to the unbroken skin. While processing mercury and its compounds, it has contact with the skin and through the skin mercury gets into the body. Mercury can also get into the human system through the eyes. The vapour of mercury can get into the eye.

Inhalation, skin contact and eye contact are associated with industrial operations, which can be termed as ‘Occupational Mercury Poisoning’.

According to Dr. Donald Hunter, the first cases of poisoning in industry occurred in manufacture of methyl mercury iodide in a factory in London in 1937. According to Bloomfield and his colleagues in 1940, in USA, there were 32,855 persons exposed to a mercury hazard. Since then a number of cases have been reported in various countries.

Few selected case histories of occupational mercury poisoning are dealt below:

Mercury Processing: West and Lim have studied the mercury poisoning amongst 281 workers employed, 96 were subject of a study that considered airborne mercury exposure levels, clinical and subjective symptoms and urinary levels. The study revealed that the workers without symptoms of poisoning who had worked 3 to 312 months had mercury levels ranging from 320–1400 µg/L.  In workers without moderate to severe cases of mercury poisoning who had worked 3 to 24 months with airborne exposure level at times exceeding 1200 µg/L. The urinary levels ranged from 950–7100 µg/L. At urinary levels of mercury over 800 µg /L, the presence and severity of symptoms and manifestations of intoxication correlated well with urinary levels. Workers with urinary mercury levels under 800 µg/L tended to have mild complications.

Mining & Milling of Cinnabar: Rentos and Sligman studied the relationship between levels of exposure to airborne mercury and clinical observations on eighty-three workers employed in the mining and milling of cinnabar. Mercury vapour levels in the mines ranged from 0.009– 0.03 mg/m3. 3 out of 17 workers exposed to mercury concentration averaging 0.21 mg/m3 and 29 out of 54 workers exposed to mercury concentration averaging 0.031 mg/m3 had clinical signs of mercury poisoning. All workers with symptoms of mercury poisoning had urinary levels in excess of 300 mg/L, the upper normal zone.

Gombos, B et. al., have done examination of 50 workers in a Czechoslovakia mercury extraction plant, who were exposed to mercury vapours in concentrations from 400–2000 µg/m3 of air. The study revealed main functional disorders of the central and vegetative nervous systems. Exposure of less than five years frequently caused gingivitis. It was found that the elimination of mercury in urine could be increased by injection of Ca EDTA.

Faleg and Lenji have studied the affections due to mercury. They have investigated a group of 300 workers in the felt hat industry (105 men and 195 women) who were suffering from chronic mercury poisoning. The result shows that 74 cases of laryngeal affections (22 men and 52 women).

Laboratory Workers: Henryka Langauer-Lewowicka, has revealed the results of observations on 6000 laboratory workers of Poland over a period of 6 years to determine disorders of the nervous system due to chronic poisoning. Subjective symptoms reported by a group of 126 workers selected on the basis of various examination included excitability, sleeplessness giddiness and headaches, debility, acroparaesthesia, apathy depression and mental weakness, even culminating complete degradation of the mental faculties.

Chemical Plants: El-Sadik and El-Dakhakhny carried out 2 study in French plant producing caustic soda by electrolysis of sodium chloride, using mercury in the electric cells. 68 workers exposed to mercury and 10 controls were studied. Neurasthenia, stomatitis, tremors, behavioural changes and increase in response to deep reflexes were found in workers with chronic mercurialsm. The presence of mercury in saliva is of diagnostic significance

Smith et. al., investigated the effects of exposure to mercury on 642 workers employed in mercury cell rooms in the manufacture of chlorine. On the basis of this, Smith suggested that an air threshold level of mercury of 0.1 mg/m3 in general corresponds to a blood mercury level of 6 mg/100 mL and urine level of 0.22 mg/L uncorrected for specific gravity. The clinical data on the exposed workers, including chest X-rays, electrocardiogram and laboratory hematologic data, were found to be normal. Abnormalities of teeth and gums, tremors and abnormal reflexes insomnia, shyness and nervousness, loss of appetite and weight; did however exhibit a dose response relation.

David and Styblova DV have conducted a study in Czechoslovakia on 56 workers employed in the electrolytic manufacture of sodium hydroxide. They conclude that the toxic effects of mercury first effects the cerebral cortex where it evokes initially a weakening of the inhibition and later a retardation of the irritation process. Only after this does the toxic effect extend to other tissues structures, especially the extra pyramidal system.

Thermometer Factory: Jenny et. al. have carried out an enquiry in three small scale workshops and some industrial establishments in France manufacturing thermometers with a view to find out the risk of mercury poisoning.  The clinical examination of 36 exposed workers revealed seven cases of confirmed chronic poisoning and six probable cases.

Burn has carried out a study in a thermometer factor employing 70 persons. The study reveals that 56 men who had employed for 1-48 years had definite evidence of mercurialentis.

Electric Meters: Lesley Bidstrup had examined 161 persons employed in repairing direct current meters. She found that 27 out of 161 were to have symptoms and signs of chronic mercury poisoning. The excretion of mercury in the urine ranged from 55-7950 µg/24 h. The atmospheric concentration of mercury were about 200 µg/m3 in the general atmosphere of some workshops and as high as 1600 µg/m3 near benches, a lathe and mercury still. In only 3 out of 11 workshops were the concentration of mercury in the working atmosphere found to consistently below the TLV of 100 µg/m3.

Dentist: Dr. Domey reported the results of a detailed survey conducted by dental students in 60 dental practices managed by 30 dentists. The result of the study shows that the concentration of mercury in the air frequently exceeded 50 µg/m3 of air. Significant difference in atmospheric contamination were found between laboratories, sites, of measurements and times of day correlated with mercury consumption, the number of amalgams per day, age of laboratories, thickness of carpeting and frequency of cleaning.

Magnaval JP, et al., has studied the occupational hazard of mercury in dental surgeries. They have studied the mercury concentration in various dental surgeries and compared them with TLVs of US (50µg/m3) and USSR (10µg/m3). The mercury levels in the hair and nails, urine and blood very often exceeded the mean value. They have drawn the attention to the possible hazard of mercury methylation in man.


According to Goldwater all forms of mercury are not equally toxic. Organomercurials used as diuretics have been administered in divided doses totalling as much as 78 grams with results beneficial to health. There is little evidence that metallic mercury is toxic by ingestion. But mercury salts are toxic by ingestion. The lethal oral dose of soluble mercury salts for man is 1.0 to 2.0 grams. The lethal oral dosage of mercury chloride for dogs is 10 to 15 mg/kg. Mercurous chloride (calomel) given to dogs at 210 mg/kg produced systemic effects. For man, a single dose of 0.5 gm. of mercuric chloride can be lethal. Much smaller amounts of methyl mercury might under some conditions cause serious illness and death.

WHO has recommended a provisional tolerable weekly intake. The tolerable weekly intake is 300 µg total mercury of which, no more than 200 µg should be present as methyl mercury. This corresponds to a provisional tolerable weekly intake of 5 µg/kg body weight of total mercury of which no more than 3.3 µg/kg body weight should be methyl mercury compounds.

According to Hoo and others a concentration of more than 100 µg Hg/100 ml of whole blood may be associated with symptoms.

In the case of individual exposure to ethyl mercury compounds, Katsunuma reports, a suspected case of poisoning, wherein he observed with a concentration of mercury in whole blood of 65 µg/100 ml. No cases with symptoms of poisoning have been reported with a blood mercury level below this figure.

In Sweden and Finland about 200 adult consumers of methyl mercury contaminated fish have shown blood levels upto 20 µg Hg/100 ml with no typical symptoms present.

It has been variously claimed that long-term inhalation of 1 mg/m3 would produce poisoning. Prolonged exposure to concentrations between 0.01 and 0.12 mg/m3 would be dangerous. Individual reactions are more important than the actual doss. The widely accepted maximum permissible concentration is 0.1 mg/m3.

According to Berglidn, Berlin and Birke et. al., methyl mercury compounds are very toxic, partly because the excretion is slow and partly because they pass through the blood brain barrier and the placenta, causing damage to the central nervous system prenatally and postnatally.

Gage claims that the alkyl mercury compounds are much more stable in the blood. They are taken upto lesser extent in the kidney and accumulate more in the brain than methoxyethyl and phenyl mercury compounds. The distribution of methyl and ethyl mercury is very different from that of mercurials. Elimination is very slow especially in man and primates and consequently there is a considerable risk of mercury accumulation. The methyl mercury radical is rather evenly distributed in the body. However methyl mercury accumulates in red blood cells in various animal species and man such that 90 % or more of the total mercury in blood is in the red blood cells. Tejning has found that the concentration of mercury in fetal blood is about 20% higher than in the mother. Ekman after experimenting in with very small doses have found that about 15% of the total body burden of methyl mercury is accumulated in the brain.

Noreseth and Clarkson held the view that more than 98% of the total mercury in the brain is in the form of methyl mercury. A similarly high proportion of the intact mercurial has been observed in blood and spleen. In the kidneys upto 40% of the mercury has been reported in the inorganic form.


As far as possible avoid high level mercury infected foods like, fish, meat, chicken and grains.  If not possible at least reduce the consumption of mercury infected foodstuffs. Occupational mercury poisoning can be prevented or reduced by using less hazardous substitutes wherever possible and in some cases processes have to be modified to exclude the use of mercury.  A high standard of cleanliness should be observed in workplaces where the substance is handled. Storage of mercury and mercury compounds should be in air-tight or water-sealed vessels.  Process should be fully enclosed or exhaust ventilation provided. Exhaust from vacuum pumps should be vented outside the workroom at a safe height.  Protective clothing including overalls, gloves, etc., should be provided to prevent skin contact and special arrangement should be made regular laundering of such clothing.  Breathing apparatus of the approved type should be provided for emergency use.


The Ministry of Environment and Forests and Climate Change (MoEFCC) is the focal point in the Government of India for all matters relating to the environment.  As the nodal ministry it co-ordinate with all other ministries. Mercury has been the focus of regulatory activity, because of its toxic and carcinogenic effects, as well as its persistent prevalence in the environment.

The various laws relating to the mercury in the environment include, Water Prevention and Control of Pollution Act & Rules, Environment (Protection) Act & Rules, Hazardous Waste (Management and Handling) Rules, Manufacture, Storage and Import of Hazardous Chemical Rules, Factories Act & Rules, Workman Compensation Act, Prevention of Food Adulteration Act & Rules, Municipal Solid Waste (Management and Handling) Rules, Public Liability Insurance Act & Rules and various standards issued by the Bureau of Indian Standards. Mercury poisoning is a compensable disease in India.

The Minamata Mercury Convention, a global treaty to protect health and the environment from the adverse effects of mercury, was signed on 10th October, 2013 at a diplomatic conference held in Kumamoto, Japan. The convention aimed to regulate a phase out mercury usage around the world.  The global treaty, came into force on 16th August, 2017. In 2014, India became a member of the United Nations Environmental Program (UNEP) led Minamata convention along with 127 other member countries.

Though, India has expressed willingness to curb mercury pollution by signing the treaty in 2014, India has not yet ratified the global treaty, thereby putting millions of lives under risk. Incidentally, China, USA, The European Union and several others have ratified the treaty and will be legally bound by its terms.  Once ratified, India would be legally bound to follow the rules issued under this convention.

The statistics regarding the quantities of mercury produced and used in India are limited. However, India is one of the major consumers of mercury, importing large quantities for use in chlor-alkali and other industrial uses.

According to the UNEP, data of 2005 industrial plants involved in burning of coal are primarily responsible for polluting the environment – with 87% of the total mercury emissions.

There is no clear data by the Government on the total mercury emission from various sectors.  However, according to a study conducted by IEA Clean Coal Centre in 2012, India is the second largest polluter of mercury in the world after China. IEA Study also claims that about 8.83% of the global total was emitted from India.

A Centre for Science and Environment (CSE) study found about 210 tons of mercury being emitted by the industrial sector during 2011-12.

In India, a major portion of mercury emission comes from burning of coal by industries, mainly coal-based power plants, gold mining plants and chlor-alkali plants, since mercury is a natural element of coal. Many studies have found that coal in India has a higher amount of mercury, which is released in the environment through gases, ash, and dust.

According to an estimate by Sanjeev Kanchan of CSE, from coal consumption, around 58% of mercury is released in gaseous form, 2.5% in particulate matter, around 32.5% goes through ash, while the remaining 7% remains unaccounted for.

Jayshree Chemical’s Chlo-Alkali plant at Odisha is identified as a mercury contaminated site by Central Pollution Control Board. Jayshree Chemical’s released its mercury contaminated waste into the nearby areas and the sludge close to the pond which is located in the bed of the Rushikulya River.

The Singroli region in Uttar Pradesh’s Sonbhadra District and Ganjam in Odisha, are the other major zones of mercury contamination in the country. According to an estimate, that a 1000 MW thermal power plant is emitting at least 500 Kg of mercury every year in Singroli region.

The CSE Green Rating Project in 2015, had conducted a study on 47 coal-based power plant across the country.  Its findings were alarming which reveal that 20 plants were discharging ash slurry, holding toxic heavy metals, directly into rivers and reservoirs, while nearly 60% of the plants analysed did not have effluent and sewerage treatment plants.  The study also found that only 50-60% of the 170 million tons of fly ash generated by the sector was being utilised while the rest was dumped into poorly designed and maintained ash plants, thus polluting land, air and water.  In such cases, mercury transforms into methyl mercury which then enters into our food chain affecting the inhabitants and other living things.

In another CSE study conducted in 2012 in Sonbhadra District, UP, average mercury content in 19 human blood samples was found to be 6 times the safe limit (5.8 ppb as per the US Environmental Protection Agency) while drinking water was found unfit for consumption without treatment. Same was the case with Rohu fishes of Rihand Reservoir. Mercury was present in all 7 soil samples.  In fact, the study found mercury level of 113.48 ppb – nearly 19 times the safe limit – in the blood sample of a resident at Khairahi Village, who used to eat fish 2 to 3 days in a week.

Since there were no standard set on mercury emission from power plants, no technology deployed by power plants in India, to control mercury emission, and most of them do not even monitor the emissions constantly.  However, MoEFCC, has reluctantly notified the standard of 0.03 mg/m3 for mercury on the recommendation of the Central Pollution Control Board.

Kodaikanal Mercury Poisoning is a proven case of mercury contamination by Hindustan Unilever Limited (HUL) in the process of making Mercury Thermometers for export around the world.  In 1983 Ponds moved its decade’s old mercury thermometer factory to Kodaikanal, bordering the dense water shed forests of Pambar Shola.  HUL acquired the factory to import mercury from the United States and to export finished thermometers back to USA and Europe.  Following complaints by its workers of Kidney related and other illness in 2001, the thermometer factory was forced to shut down, open up a series of issues in India such as liability, corporate accountability and corporate negligence. In 2003, HUL was forced to export 289 tons of mercury contaminated materials to a mercury recycling facility in USA as there was no facility to treat mercury waste in India. In 2016, HUL finally settled compensation for its former workers.

According to Mr. Nityanand  Jayaraman, a Chennai based writer and activist, who has been part of the campaign since 2001, HUL is leaving up to 25 mg/Kg of mercury in soil, and he claims that this is 250 times higher than the naturally occurring background levels, even after a clean-up. On June 11, 2018, HUL received permission from Tamil Nadu Pollution Control Board (TNPCB) to commence full scale soil remediation to the remedial standard of 20mg/kg at its former factory site in Kodaikanal.    Incidentally, Greenpeace estimates that just ONE gram of mercury deposited annually can, in the long term, contaminate a lake spread of 25 acres to the extent that fish from the lake are rendered unfit for human consumption.


Mercury is a naturally occurring element. It can exist in coal in gaseous, liquid, or solid form. Possessing the property of a liquid and a metal at room temperature, mercury is commonly used in many consumer products. Mercury may be deposited into water bodies either directly from water discharge. Microorganisms then convert elemental mercury to highly toxic methyl mercury, which can be readily absorbed by aquatic organisms. Mercury poisoning is a type of metal poisoning due to mercury exposure.  In India, a major portion of mercury emission comes from burning of coal by industries, mainly coal-based power plants, gold mining plants and chlor-alkali plants. Forms of mercury exposure include metal, vapour, salt and organic compounds. Mercury can be inhaled, ingested or absorbed through the skin. Most exposure is from eating fish, amalgam based dental fillings, or exposure at workplaces. Mercury’s primary health effects are neurological, but it can also cause serious damage to the kidneys. Human activities that release mercury into the environment include the burning of coal and mining of gold. Mercury poisoning can be determined by testing the samples of blood, urine and hair. Prevention includes eating a diet low in mercury and avoiding mercury vapour.

Article by —–

Mr. R.R. Nair, Chief Executive, Safety and Health Information Bureau, Vashi, Navi Mumbai
Mr. R.R. Nair,
Chief Executive,
Safety and Health Information Bureau,
Vashi, Navi Mumbai

Mr. R. R. Nair is currently the Director of Safety and Health Information Bureau. He is an ex-employee of Central Labour Institute, DGFASLI, Mumbai, and retired from the Government Service after 28 years. He has more than 50 years’ experience in occupational safety, health & fire protection. He participated in a number of seminars, conferences, workshops on safety, health and fire protection at National and International levels. He has carried out about 85 projects in safety, health, environment and fire protection (safety audits, accident investigations, environmental studies, hazard identification and risk assessment (HIRA), hazardous zone classifications, fire safety audits in high rise buildings, etc.) PAN India. He is author of 15 books and about 80 articles in various topics on safety and allied subjects.

He can be contacted on:
M: +91 7045172050, +91 9224212544
Resi: +91 477 2266994
E-mail: /

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