Some science behind the scenes

Mercury poisoning - Sources

On reviewing the various sources of mercury poisoning one thing struck me about the evidence I accumulated. Mercury has been a known toxin for several hundred years and yet it continues to be used in consumer products and released into the atmosphere as toxic waste. I found this almost unbelievable.

We all are aware that many manufacturers and government officials either ignore the risk because of the profit or ‘job survival’ motive, or somehow think it ‘won’t happen’ or even seem unaware of the risk even after all this time. But you would think that they must realise that by polluting the atmosphere and the world with mercury they suffer too, they are as likely to get poisoned as the rest of us.

The most frequent source of mercury exposure is open to debate. On an individual exposure basis, the estimated intake and retention of elemental mercury vapor (from dental amalgams and atmospheric pollution) in non-occupationally exposed individuals has a much broader range (3.9-21.0 ìg/day) than either inorganic (4.3 ìg/day) or methylmercury (1-6 ìg/day) exposure.

But as you will see from the following list we can be exposed to mercury in numerous ways, and in many cases have no idea it is happening.

Food contamination

  • Fish contamination - Any discharge of mercury into the sea will have an impact upon fish stocks.   Methylation of the metal by plankton and its subsequent incorporation into the food chain can cause acute toxicity in all the victims eating fish caught in that region from killer whales, polar bears and dolphins to human beings. Although immediate fatalities may be few, long term effects can be serious.  Children, adults and animals can develop degenerative neurological disorders such as paraesthesia, ataxia, dysarthria, hearing and visual loss. In Japan, for example, cerebral palsy has persisted at a high 6% incidence of births.

Fresh water contamination also occurs. The Native American Indians, for example,  experienced mercury poisoning from Dryden Chemical Company, a chloralkali process plant, located in Dryden, Ontario that supplied both sodium hydroxide and chlorine used in large amounts for bleaching paper during production for the Dryden Pulp and Paper Company. Dryden Chemical company discharged their effluent into the Wabigoon-English River system.  The Ontario provincial government initially told the First Nation communities to stop eating fish — their main source of protein — and closed down their commercial fishery. Closing of the commercial fishery meant economic disaster for the Indian Reserve. The closure also affected the tourism industry, where locals acted as guides for out of town fisherman. Walleye in local waterways are no longer safe to eat due to mercury contamination.  Both the paper and chemical companies ceased operations in 1976.

There are currently 1,782 advisories (one per body of water) issued by the U.S. Environmental Protection Agency (EPA) in 41 states in the United States restricting the consumption of any locally caught fish or shellfish due to their mercury content. Sixteen states have issued statewide or statewide-coastal advisories recommending restricting the consumption of fish caught in the state or along the coastline due to methylmercury contamination.

In December 2008, actor Jeremy Piven was diagnosed with mercury poisoning  resulting from eating sushi twice a day for twenty years. Actress Daphne Zuniga was diagnosed with mercury poisoning after eating sushi four times a week.

Although I have cited the USA, the problem is worldwide.  It is of course a particular problem in places that eat a lot of fish and pollute, Japan, for example, Russia, even Scandinavia. Anyone who routinely consumes contaminated fish, for example, subsistence hunters who consume meat or organ tissues of marine mammals or feral wildlife, are at great risk.

Outbreaks of methylmercury poisoning occurred in several places in Japan during the 1950s due to industrial discharges of mercury into rivers and coastal waters. The best-known instances were in Minamata and Niigata. In Minamata alone, more than 600 people died. More than 21,000 people filed claims with the Japanese government, of which almost 3000 became certified as having the disease. In 22 documented cases, pregnant women who consumed contaminated fish showed mild or no symptoms but gave birth to infants with severe developmental disabilities.

Whale and dolphin meat - Consumption of whale and dolphin meat, as is the practice in Japan, is a source of high levels of mercury poisoning. Tetsuya Endo, a professor at the Health Sciences University of Hokkaido, has tested whale meat purchased in the whaling town of Taiji and found mercury levels that are more than 20 times the acceptable Japanese standard.

  • Plant and livestock contamination - Plants and livestock may contain mercury due to bio-accumulation of mercury from soil, water and atmosphere, and due to bio-magnification by ingesting other mercury-containing organisms. Chickens fed fish-meal, for example, may contain mercury. Exposure to mercury can also occur from eating foods that have acquired mercury residues during processing.

Agriculture and gardening

  • Fungicide contamination – wheat or other foodstuffs treated with fungicide containing mercury compounds can cause mercury poisoning.  For example, widespread mercury poisoning occurred in rural Iraq in 1971-1972, when grain treated with a methylmercury-based fungicide that was intended for planting only was used by the rural population to make bread, causing at least 6530 cases of mercury poisoning and at least 459 deaths.
  • Gardening – Mercury(I) chloride is also known as calomel.   Until fairly recently it was also used as a horticultural fungicide, most notably as a root dip to help prevent the occurrence of clubroot amongst crops of the Brassicaceae family.

Medical procedures

  • Dental treatment -Dental amalgam is an alloy of about 50 percent elemental mercury. It  was first introduced in France in the early 19th century. Chosen for its cost-effective durability, this amalgam is a source of low-level exposure to mercury vapour, and an enormous amount of controversy. Mercury cannot vaporise in the mouth from a filling. If you grind your teeth then mercury amalgam may enter the stomach and intestines, but as we have seen, less than 0.01% of ingested mercury is absorbed through the intact gastrointestinal tract; though it may not be true for individuals suffering from ileus. The time when you are at risk is during dental treatment when for example, an old filling is drilled out and mercury vapour is produced by the heat from the drill.  Dentists are probably more at risk than their patients.

    Although the vast majority of patients with amalgam fillings are exposed to levels believed to be too low to pose any risk to health, there are some patients (i.e., those in the upper 99.9 percentile) who exhibit urine test results that are comparable to those at the maximum allowable legal limits for workplace (occupational) safety. In Norway, amalgam fillings are banned due to concerns over public health and environmental pollution.  But Norwegians eat a lot of fish – so where is the mercury really coming from?  In 2002, the World Health Organization Task Group on Environmental Health Criteria for Inorganic Mercury, concluded: "With reference to the fact that mercury is a multi-potent toxin with effects on several levels of the biochemical dynamics of the cell, amalgam must be considered to be an unsuitable material for dental restoration."
  • Vaccination - While the usage of mercury in medicine has declined, mercury-containing compounds are still used medically in vaccines, this is the subject of controversy regarding their potential for mercury poisoning.  The main culprit in vaccines is Thiomersal. I described Thiomersal earlier.Thiomersal has been used as a preservative in vaccinations since the 1930s. It is currently mixed with DTaP, HIB, and hepatitis B vaccines or is used in the manufacturing process for vaccines, with resultant trace amounts being present in the final product. Based on existing Centers for Disease Control (CDC) recommendations for vaccinations, a typical six-month-old child, if receiving all thimerosal-containing vaccines, could potentially be injected with as much as 187.5-200 μg of methylmercury; the equivalent of more than 1.0 μg per day. This amount exceeds the reference limits for exposure to mercury set by the EPA of 0.1 μg/kg/day.

    Because of the risks, thiomersal has been phased out of most US and European vaccines. Outside North America and Europe, many vaccines contain thiomersal. However, even in the US and Europe, it is still being used in some preparations of influenza vaccine and in several vaccines that are not routinely recommended for young children, including DT (diphtheria and tetanus), Td (tetanus and diphtheria), and TT (tetanus toxoid); other vaccines may contain a trace of thiomersal from steps in manufacture.
  • Snake or spider bite treatments - four rarely used treatments for pit viper, coral snake, and black widow venom still contain thiomersal.
  • Skin testing for antigensThiomersal is used as a preservative in skin test antigens.  Thiomersal is used in patch testing for people who have dermatitis, conjunctivitis, and other potentially allergic reactions. A 2007 study in Norway found that 1.9% of adults had a positive patch test reaction to thiomersal; a higher prevalence of contact allergy (up to 6.6%) was observed in German populations.
  • Other Medical procedures - Because mercury passes through the GI tract without being absorbed, it was once used medically. For example, elemental mercury was used to mechanically clear intestinal obstructions (due to its great weight and fluidity). The toxic effects often were either not noticed at all or so subtle or generic that they were attributed to other causes and were not recognized as poisoning caused by mercury.

Over the counter and other medicines

  • Herbal medicines – appear to be occasionally contaminated with mercury.

Contamination and adulteration of herbal medicinal products (HMPs): an overview of systematic reviews - Posadzki P,  Watson L, Ernst E;  Complementary Medicine, Peninsula Medical School, University of Exeter, Veysey Building, Salmon Pool Lane, Exeter, EX2 4SG, UK

The aim of this overview of systematic reviews is to summarise and critically evaluate the evidence from systematic reviews of the adulteration and contamination of herbal medicinal products (HMPs).

Five electronic databases were searched to identify all relevant systematic reviews.

Twenty-six systematic reviews met our inclusion criteria. The most commonly HMPs were adulterated or contaminated with dust, pollens, insects, rodents, parasites, microbes, fungi, mould, toxins, pesticides, toxic heavy metals and/or prescription drugs. The most severe adverse effects caused by these adulterations were agranulocytosis, meningitis, multi-organ failure, perinatal stroke, arsenic, lead or mercury poisoning, malignancies or carcinomas, hepatic encephalopathy, hepatorenal syndrome, nephrotoxicity, rhabdomyolysis, metabolic acidosis, renal or liver failure, cerebral edema, coma, intracerebral haemorrhage, and death. Adulteration and contamination of HMPs were most commonly noted for traditional Indian and Chinese remedies, respectively.

Collectively these data suggest that there are reasons for concerns with regards to the quality of HMPs. Adulteration and contamination of HMPs can cause serious adverse effects. More stringent quality control and its enforcement seem to be necessary to avoid health risks.

PMID: 22843016

  • Calomel– Acrodynia is a type of mercury poisoning.  It  was relatively commonplace among children in the first half of the 20th century. At first, the cause of the acrodynia epidemic among infants and young children was unknown; however, mercury poisoning, primarily from calomel in teething powders, began to be widely accepted as its cause in the 1950s and 60s.
  • Syphilis treatments – mercury was at one time used in the treatment of syphilis before the advent of antibiotics. It was inhaled, ingested, injected, and applied topically. Poisoning was so common that its symptoms were confused with those of syphilis. This usage of "salts of white mercury" is referred to in the English folk-song, The Unfortunate Rake.
  • Disinfectants – mercury has been used in disinfectants.  The term Hunter-Russell syndrome derives from a study of mercury poisoning among workers in a seed packing factory in Norwich, England in the late 1930s who breathed methylmercury that was being used as a seed disinfectant and preservative.
  • Opthalmic and nasal products – Thiomersal is commonly known in the US as thimerosal, and has been used as a preservative in Opthalmic and nasal products.
  • Ayurvedic medicines – rather alarmingly occasionally contain high levels of a number of heavy metals.

Heavy metal content of ayurvedic herbal medicine products - Saper RB, Kales SN, Paquin J, Burns MJ, Eisenberg DM, Davis RB, Phillips RS;  Division for Research and Education in Complementary and Integrative Medical Therapies, Osher Institute, Harvard Medical School, Boston, USA.

Lead, mercury, and arsenic intoxication have been associated with the use of Ayurvedic herbal medicine product (HMPs).

To determine the prevalence and concentration of heavy metals in Ayurvedic HMPs manufactured in South Asia and sold in Boston-area stores and to compare estimated daily metal ingestion with regulatory standards.

Systematic search strategy to identify all stores 20 miles or less from Boston City Hall that sold Ayurvedic HMPs from South Asia by searching online Yellow Pages using the categories markets, supermarkets, and convenience stores, and business names containing the word India, Indian cities, and Indian words. An online national directory of Indian grocery stores, a South Asian community business directory, and a newspaper were also searched. We visited each store and purchased all unique Ayurvedic HMPs between April 25 and October 24, 2003.

Concentrations (microg/g) of lead, mercury, and arsenic in each HMP as measured by x-ray fluorescence spectroscopy. Estimates of daily metal ingestion for adults and children estimated using manufacturers' dosage recommendations with comparisons to US Pharmacopeia and US Environmental Protection Agency regulatory standards.

A total of 14 (20%) of 70 HMPs (95% confidence interval, 11%-31%) contained heavy metals:
lead (n = 13; median concentration, 40 microg/g; range, 5-37,000),
mercury (n = 6; median concentration, 20,225 microg/g; range, 28-104,000),
and/or arsenic (n = 6; median concentration, 430 microg/g; range, 37-8130).
If taken as recommended by the manufacturers, each of these 14 could result in heavy metal intakes above published regulatory standards.

One of 5 Ayurvedic HMPs produced in South Asia and available in Boston South Asian grocery stores contains potentially harmful levels of lead, mercury, and/or arsenic. Users of Ayurvedic medicine may be at risk for heavy metal toxicity, and testing of Ayurvedic HMPs for toxic heavy metals should be mandatory.

  • Antiseptics - Merbromin (marketed as Mercurochrome, Merbromine, Sodium mercurescein, Asceptichrome, Supercrome, Brocasept and Cinfacromin) is a topical antiseptic still  used for minor cuts and scrapes. It is an organomercuric disodium salt compound. It is still readily available in a number of countries but no longer sold in the United States, Germany, or France because of its mercury content.  When applied on a wound, it stains the skin bright red.  Mercurochrome has been designated as unsafe and ineffective by the U.S. Food and Drug Administration (FDA) due to concerns about its mercury content. Other obsolete organomercury antiseptics include bis-(phenylmercuric) monohydrogenborate (Famosept).
  • Diuretics – Mercurial diuretics cause diuresis by reducing the reabsorption sodium in the ascending loop of Henle, thus causing more water being delivered to the distal convoluted tubule. Unfortunately, earlier physicians misconstrued hallmark symptoms of mercury poisoning such as excessive salivation as signs of mercury's efficacy.  Believe it or not this belief continued up until the 1960s when the use of mercurial diuretics were halted in medicine.  In theory there should be none of these products on the market, but we can never be sure can we?  Some common organic mercurials include:  Mersalyl acid (Mersal) (Salyrgan) ; Meralluride ; Mercaptomerin ; Mercurophylline and Merethoxylline procaine.
  • Laxatives – Mercury(I) chloride also known as calomel – described earlier -  was taken internally and used as a laxative until the early 20th century.
  • Nappy rash treatments and vaginal contraceptives – you may think you are reading this wrong, but mercury containing compounds were used for both.    Nitromersol (metaphen), for example,  is a mercury-containing organic compound that is primarily used as an antiseptic and disinfectant.   It was confirmed as an animal carcinogen and is known to emit toxic fumes of NOx and mercury when destroyed by heat. However up until 1998, nitromersol (and other mercury-containing products) were used as first-aid antiseptics for diaper rash and vaginal contraceptives.  In 1998 they were outlawed by the FDA but unfortunately not outlawed elsewhere.

Nitromersol is still in use as a preservative for vaccines and antitoxins

  • Ointments - Mercuric amidochloride is an inorganic compound with the formula HgNH2Cl

    It arises from the reaction of ammonia and mercuric chloride. Addition of base converts it into "Millon's base," which has the formula [Hg2N]OH(H2O)x.

    Before the toxicity of mercury was appreciated, mercuric amidochloride, known as "ammoniated mercury", was used as a a topical antiseptic and disinfectant.

    It may still be available.

A second type of parcel delivered through the Red Cross during World War II was the Red Cross Prisoner of War First Aid Safety Kit, which was supplied by the American Red Cross for distribution through the International Committee. Such parcels generally held the following items:

  • A twelve-page booklet with instructions for use of the enclosed medical supplies, printed in English, French, German, Polish and Yugoslav
  • Ten packages of sterilized gauze, in two different sizes
  • One package containing 500 laxative pills
  • Two packages containing 500 aspirin tablets each
  • Twelve gauze bandages
  • Two cans of insecticide powder
  • Four tubes of boric acid antiseptic ointment
  • Two packages containing 500 sodium bicarbonate tablets each
  • Two tubes of Salicylic ointment (for treatment of athlete's foot and similar fungal diseases)
  • Two tubes of Mercuric antiseptic ointment
  • Four tubes of sulphur ointment (for treatment of skin diseases)
  • One box containing 100 band-aids
  • Two rolls of adhesive tape
  • Two one-ounce packages of absorbent cotton
  • Safety pins, forceps, soap, disinfectants and scissors
  • Scabies treatments – an ointment was once used for scabies that contained mercury.  It killed Jonathan Swift’s father.

Shakespeare’s Tremor and Orwell’s cough – Dr John Ross

Scabies is a mite that chomps its way through the superficial layers of the skin, trailing eggs and faeces as it goes.  These leavings are intensely irritating. People that are infected may be kept awake all night, frantically scratching their armpits, waist, and groins.  Mercury ointment is an ancient cure. …. exposure to mercury …in high enough doses .. leads to kidney failure, as it makes the lining of the kidney tubules slough off.

Waste disposal

  • Hazardous waste sites - hazardous waste sites “pose one of the most significant potential threat to human health due to their known or suspected toxicity and the frequency of exposure.” Of 1,467 hazardous waste sites listed in the United States National Priorities List in 1998, for example, toxic levels of mercury were identified in 714.
  • Incineration of waste - In the United States alone – ironies of ironies  - 26 percent (64.7 tons/year) of atmospheric mercury emissions come from medical waste incineration.
  • Recycling facilities and municipal incinerators – also pose a threat.  Disposal of mercury-containing domestic batteries on council dumps, for example, poses an enormous ecological problem. It was estimated in the US in 1989 that discarded household batteries accounted for 86% of dumped mercury.
  • Computer part recycling – When recycling computer parts, mercury is occasionally used to extract the gold used.  On March 19, 2008, Tony Winnett, 55, inhaled mercury vapors while trying to extract gold from computer parts (by using liquid mercury to separate gold from the rest of the alloy), and died ten days later. His Oklahoma residence became so contaminated that it had to be gutted.


Mercury poisoning used to be widespread in such industries as mirror making. In Western countries, the use of mercury in industrial processes has almost disappeared, but it has not in eastern countries. In modern times, exposure in the west  and therefore toxicity is limited mainly to thermometer, barometer and mercury arc equipment manufacture; as well as pigment, fungicide, insecticide and dry cell battery manufacture.

  • Paper manufacturing - Mercury compounds were once used extensively in the production of paper and Sweden was found to be dumping enormous quantities of mercury-rich effluent from its paper industry into the sea. Pressure from environmentalists is thought [but not known] to have eradicated mercury used in paper-making for good.
  • Hat making - The phrase mad as a hatter  is a reference to mercury poisoning, as mercury salts were once used in the manufacture of felt hats in the 18th and 19th century. Absorption of these compounds through the skin gave rise to body burdens sufficient to cause the symptoms of madness among this profession. The Mad Hatter character of Alice in Wonderland is an example of the effects!  Lewis Carroll would have been familiar with the phenomenon of ‘madness’ that occurred among hatters, but might not have been aware of the cause.
  • Laboratory exposure – Anyone working in a laboratory that uses mercury based products is at risk.  On August 14, 1996, Karen Wetterhahn, a chemistry professor working at Dartmouth College, USA spilled a small amount of dimethylmercury on her latex glove. She began experiencing the symptoms of mercury poisoning five months later and, despite aggressive chelation therapy, died a few months later from brain malfunction due to mercury intoxication. An early scientific study of mercury poisoning was in 1923–6 by the German inorganic chemist, Alfred Stock, who himself became poisoned, together with his colleagues, by breathing mercury vapor that was being released by his laboratory equipment—diffusion pumps, float valves, and manometers—all of which contained mercury, and also from mercury that had been accidentally spilt and remained in cracks in the linoleum floor covering.
  • Tanning  - tanning can be performed with either vegetable or mineral methods. Before tanning, the skins are unhaired, degreased, desalted and soaked in water over a period of 6 hours to 2 days. To prevent damage of the skin by bacterial growth during the soaking period, ‘biocides’ are used.  Up until 1980 the tanning industry used pentachlorophenol and quicksilver (mercury base) biocides and their derivatives.
  • Gilding – Mercury poisoning was an occupational hazard of gilders, who used quicksilver in the manufacture of gold leaf


  • Mercury mining – Mercury mining was and still is an extremely hazardous occupation, but what may not be known is that even being near a mercury mining site can be hazardous.  The ATSDR considers anyone who lives in close proximity to a former mercury mining site to be at risk from mercury poisoning.
  • Gold extraction and mining - There is international concern at present over the illegal dumping of thousands of tonnes of mercury every year, used for extraction of gold from ore, in the Brazilian Amazon area. Many hundreds of cases of mercury toxicity have been reported in the area and ecologists are very concerned about health effects once the water table is contaminated. More primitive gold extraction techniques involve boiling off mercury from gold-mercury amalgam in open pots over a fire.

    Small independent gold mining operation workers are at higher risk of mercury poisoning because of crude processing methods. Such is the danger for the galamsey in Ghana and similar workers known as orpailleurs in neighboring francophone countries. While there are no official government estimates of the labor force, observers believe 20,000-50,000 work as galamseys in Ghana, a figure that includes many women, who work as porters.

Natural sources

Annual worldwide emissions of mercury into the atmosphere have been estimated at 2,200 metric tons.  One-third of these emissions are estimated to originate from natural sources, for example, volcanic eruptions and decay of mercury-containing sediment.

Fossil fuels

Twenty-five percent of total worldwide emissions of mercury come from fossil fuel combustion. Anyone, for example, living near a coal-fired electric generating plant is at risk from mercury toxicity.

Domestic consumables

  • Cosmetics - Some skin whitening products contain the toxic chemical mercury(II) chloride as the active ingredient. When applied, the chemical readily absorbs through the skin into the bloodstream. The use of mercury in cosmetics is illegal in the United States. However, cosmetics containing mercury are often illegally imported. The use of skin whitening products is especially popular amongst Asian women. In Hong Kong in 2002, two products were discovered to contain between 9,000 to 60,000 times the recommended dose.
  • Fluorescent lamps -  contain mercury released when bulbs are broken. Mercury in bulbs is typically present as either elemental mercury liquid, vapor, or both, since the liquid evaporates at ambient temperature.If a bulb is carelessly thrown away in a rubbish bin and thereby breaks, bulbs may emit sufficient mercury vapor to present health concerns.  Given the Government emphasis upon energy efficiency and the increase in use of such bulbs, the cause for concern is greater, especially since much waste is crushed when collected by waste disposal lorries releasing the mercury into the atmosphere.  The dangers of exposure should not be underestimated.  A 1987 report described a 23-month-old toddler who suffered anorexia, weight loss, irritability, profuse sweating, and peeling and redness of fingers and toes. This was traced to exposure of mercury from a carton of 8-foot fluorescent light bulbs that had broken in a potting shed adjacent to the main nursery.
  • Paint – paint contains mercury and those living or working in buildings painted with mercury-containing latex paint are considered at significant risk. Mercury-containing latex paint was removed from paint manufacturing in the USA at least 1991 but may still be available in the reserve inventories of contractors and warehouses and worldwide may not be banned.

Other miscellaneous sources

  • Cremation - there is concern about the risk to health of mercury vapour discharged from crematoria as a result of incineration of people with amalgam fillings. Certainly, toxic mercury vapour is measurable in the air downwind from crematoria when this occurs.
  • Tattooing – Thiomersal is commonly known in the US as thimerosal, and is an organomercury compound. I have described its use earlier in this section.  It has been used as a preservative in tattoo inks.