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mercury poisoning

 
Britannica Concise Encyclopedia: mercury poisoning
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Harmful effects of mercury compounds. Manufacture of paints, various household items, and pesticides uses mercury; the finished product and the waste products released into air and water may contain mercury. The aquatic food chain can concentrate organic mercury compounds in fish and seafood, which, if eaten by humans, can affect the central nervous system, impairing muscle, vision, and cerebral function, leading to paralysis and sometimes death (see Minamata disease). Acute mercury poisoning causes severe digestive-tract inflammation. Mercury accumulates in the kidneys, causing uremia and death. Chronic poisoning, from occupational inhalation or skin absorption, causes metallic taste, oral inflammation, blue gum line, extremity pain and tremor, weight loss, and mental changes (depression and withdrawal). Drugs containing mercury can cause sensitivity reactions, sometimes fatal. In young children, acrodynia (pink disease) is probably caused by an organic mercury compound in house paints.

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Dental Dictionary: mercurialism
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n

(mercury poisoning), 1. poisoning resulting from the ingestion of pure mercury, its salts, or its vapor. Manifestations of acute intoxication include nausea, vomiting, abdominal cramps, oral and pharyngeal pain, uremia, dehydration, diarrhea, and shock. Manifestations of chronic poisoning include hyper-salivation, diarrhea, vertigo, depression, intention tremor, and stomatitis. See also acrodynia and stomatitis, mercurial. n 2. poisoning by ingestion or absorption of mercury compounds. See also line, mercurial.

Alternative Medicine Encyclopedia: Mercury Poisoning
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Definition

Mercury poisoning occurs when a person has ingested, inhaled, or had skin or eye contact with the toxic (poisonous) heavy metal mercury and suffers damage to his/her nervous system and other systems of the body. Mercury, which has the chemical symbol of Hg, is one of a few elements that are liquid at room temperature; and because it easily converts to gas form, it is extremely volatile. There are three forms of mercury circulating throughout the environment, and all three forms are toxic to humans and many other living organisms in varying degrees.

Elemental mercury, also known as quicksilver, is mercury in its metallic (solid), elemental form. Elemental mercury is also referred to as mercury-zero. It is frequently found in the home in glass thermometers. It is also found in fluorescent light bulbs, thermostats, some pesticides, switches, preservatives, some paints, and in some dental amalgam fillings—although there are often mercury-free options available. In the past, according to a State of Michigan publication titled Mercury Poisoning, it was used as the active ingredient in ointments, animal worming medicines, antiseptics, disinfectants, diuretics and fungicides. Today, the publication states, it is present in seed fungicides, anti-slime fungicides used by the pulp and paper industries, by-products of burning coal, mining tailings (residue), and wastes from chlorine-alkali industries. In its solid state, elemental mercury is less toxic than some of its other forms, but is still very volatile. The most toxic effect of elemental mercury is when its extremely dangerous vapor is inhaled. This happens most likely in an industrial setting.

Elemental mercury can be converted by bacteria into a charged ion (an electrically charged atom or group of atoms) known as mercury-two. There are two dangerous aspects to this form. First, unlike elemental mercury, it readily dissolves in water and combines with other ions to form new compounds. Also, bacteria can change mercury-two into one of mercury's most toxic organic compounds, methyl mercury, which is easily soluble (capable of being dissolved) in water and thus finds its way into the food chain, where it poisons fish and other animals. Unfortunately, methyl or organic mercury accumulates in fish and many have such high levels that they become unsafe to eat. Methyl mercury is particularly dangerous for the developing fetus, babies, and young children. Pregnant women and women who may become pregnant need to be aware of the dangers of mercury exposure through eating fish.

Inorganic mercury takes the form of various compounds known as mercuric salts. Mercuric salts are used in various folk medicines, particularly in some Chinese herbal preparations and in some Mexican remedies. Exposure to mercuric salts over the long term can cause kidney and nerve damage.

Description

Many people do not take the risk of mercury poisoning seriously because they have played with elemental or liquid mercury or broken thermometers containing mercury without ill health effects. While these "small" mercury exposures can appear to be free of detectable health consequences, even a small spill can have serious effects, including hospitalization and even death, if improperly cleaned up, if there is poor ventilation, or the mercury is exposed to heat. It is extremely important, therefore, that any mercury spill, even a small one, be properly cleaned up. If not, the home, workplace, and other people may be contaminated. This is because poisoning from elemental mercury is most likely due to inhalation of mercury vapors. The danger lies in the fact that after it is inhaled into the lungs in vapor form, mercury passes into the blood stream. This is an emergency that necessitates an immediate hospital visit.

Inhalation of mercury vapor might happen in a factory where mercury is used. Most small household spills of elemental mercury are not dangerous if cleaned up sensibly. Elemental mercury usually passes right through the body if swallowed, so this is usually not poisonous to a person with a healthy digestive system. Elemental mercury is not easily absorbed by the skin, so touching elemental mercury is usually not enough to cause poisoning. But if elemental mercury is spilled in the home, from a broken thermometer or fluorescent light, for example, it must be correctly and carefully cleaned up. It should not be swept up with a broom or vacuumed, because this can break the mercury into small particles and spread it. Spilled mercury should be sucked up with an eyedropper, scooped up with paper, or picked up with sticky tape. Then the mercury should be sealed in three layers of plastic bags and disposed of according to local hazardous waste procedures. Any clothes or rags that might have gotten mercury on them should also be discarded—not washed in a washing machine as this may further spread the mercury. The area of the spill should be ventilated for several days, if possible.

Inorganic mercury, or mercury salts, have long been used in folk medicines. Exposure to inorganic mercury through folk medicines can cause poisoning. This can lead to kidney damage, tissue death, and nerve damage. Calomel, or mercurous chloride, and cinnabar, or mercuric sulfide, are two common toxic inorganic mercury compounds that should not be ingested. Folk medicines containing calomel, cinnabar, or other mercuric salts should also not be used on the skin.

Several Chinese herbal medicines have been identified as containing dangerous amounts of mercury and arsenic. These are usually prepared as an herbal ball. Known Chinese herbal medicines to avoid are: An Gong Niu Huang Wan; Da Huo Luo Wan; Niu Huang Chiang Ya Wan; Niu Huang Chiang Hsin Wan; Ta Huo Lo Tan; Tsai Tsao Wan; and Dendrobium Moniliforme Night Sight Pills.

Poisoning from organic mercury is perhaps the most troubling form of mercury exposure. Organic mercury is widespread in the environment, and scientists and government regulators are uncertain how best to clean it up and how quickly to proceed. Some mercury finds its way into the atmosphere naturally, from volcanoes for example. But much of the mercury that finds its way into our food derives from industrial pollution. Mercury is emitted by power plants that burn fossil fuel and travels through the air. It deposits in bodies of water, where it is first taken up by plankton (floating animal and plant life). Fish that feed on plankton accumulate organic mercury in their bodies, and fish that eat those fish accumulate even more. This process, called bioaccumulation, concentrates the mercury in animals at the top of the food chain.

Because mercury can travel great distances through the air, the problem of mercury pollution affects all of North America and is a global environmental problem. In the United States, the Environmental Protection Agency (EPA) is responsible for monitoring mercury emissions. In 2004, the EPA promulgated new rules on mercury emissions, which were criticized by some politicians and environmental groups as too lenient. The Food and Drug Administration (FDA), the United States government agency responsible for food safety, has revised its findings on the mercury in fish several times over the early 2000s.

As of 2004, FDA guidelines recommend that pregnant women, women of childbearing age who might become pregnant, nursing mothers, and young children all limit the amount of fish they eat, because of the danger of mercury poisoning. People in these categories should avoid eating any shark, tilefish, swordfish, and king mackerel. They are all large fish at the top of the food chain, and they are the most likely to contain high levels of mercury in their flesh. People in these categories should also eat no more than one six-ounce can of tuna per week and should limit their overall consumption of fish to no more than 12 ounces a week. This translates to about two or three meals of fish or shellfish a week. The FDA guidelines also suggest that women and children should mix the types of fish they eat, and not eat the same kind of fish or shellfish for multiple meals within a single week.

The FDA guidelines of 2004 did not address the problems of mercury exposure in people other than children, pregnant women, nursing mothers, and women of childbearing age. Some studies suggest that mercury exposures of up to four times the limits in the FDA guidelines may be safe for other people. There are many health benefits to eating fish, and the mercury level in any individual fish meal may vary greatly. So individuals not covered by these guidelines must use their own judgment on how much fish to consume. In addition, most states in the United States post warnings on consuming fish or certain types of fish caught in lakes and streams. Specific bodies of water or specific species of fish may have been found to be more dangerous than others. People who fish for sport or for subsistence should check with local government agencies about warnings on eating fish caught in their locale.

Causes & Symptoms

Common home products that contain elemental mercury, such as lights, thermostats, thermometers, and appliances are not dangerous to humans unless they are broken, mercury is released, and there is exposure to mercury vapors because of improper cleanup.

In June 1997, Karen Wetterhahn, 48, a Dartmouth College cancer research scientist whose specialty was dangerous heavy metals, died of dimethyl mercury poisoning, ten months after she spilled one to several drops of it on her rubber gloves while she was studying how mercury prevents cells from repairing themselves. Tests after the spill revealed that the mercury could pass quickly through the rubber latex gloves without damaging them. Three months after the spill, Dr. Wetterhahn experienced two episodes of nausea and vomiting. Two months later, she began losing her balance and having speaking and hearing difficulties. At the time she was hospitalized, tests showed 80 times the lethal dose of mercury in her blood. She then went into a coma until her death. The chairman of the Dartmouth chemistry department, John S. Winn, said, "I think all of us here at the chemistry department and colleagues of here in this area of research around the world have all been stunned that the gloves she was wearing at the time were not sufficient protection." He explained that although methyl mercury looks like water, it is three times as dense and is readily absorbed by the body. He also said that about 100 laboratories around the world work with dimethyl mercury. Dartmouth officials in a letter to the American Chemical Society, urged those who work with dimethyl mercury to wear neoprene gloves with long cuffs and to have frequent blood and urine testing.

Walter Crinnion, N.D. is a naturopathic doctor. He received his degree in Naturopathic Medicine from Bastyr University in Seattle, Washington, in 1982. Naturopathy originated in European health spas that emphasized hydro (water) therapy, massage, and nutritional and herbal treatment, and developed into a general philosophy of using the body's natural healing capacity to avoid surgery and drugs. After opening a family practice, he began to specialize in allergies and treating chronic health problems caused by environmental chemical overload. He today operates a cleansing facility to treat chemically poisoned people, lectures at both naturopathic and allopathic conventional medicine) medical conferences and at several naturopathic colleges, and publishes in peer-reviewed journals on the topic of environmental overload.

In 1963, a new filling for dental cavities, non-gamma-two amalgam, was introduced as a solution to conventional amalgam being prone to corrosion and mechanical weakness. Non-gamma-two amalgam quickly caught on, despite the fact that it caused a much-increased mercury emission, and replaced conventional amalgam. In the early 1980s, dentists were regularly using elemental mercury amalgam for dental fillings. However, dentists and other health professionals who had turned to holistic or alternative medicine began to publicize the toxicity of amalgam fillings and advocate their replacement with a non-toxic composite material. At first, the American Dental Association (ADA) denied there was any danger from mercury amalgam fillings. As evidence piled up, the ADA's position became that the amount of mercury leakage from them wasn't significant enough to be dangerous.

In an article entitled "Environmental Medicine: Excerpts from Articles on Current Toxicity, Solvents, Pesticides and Heavy Metals," Dr. Crinnion described his findings about the toxic aspects of elemental mercury amalgam dental fillings. According to Dr. Crinnion, silver amalgam dental fillings typically weight 1.5–2.0 g. Fifty percent of those filings is elemental mercury; and when studied, people with amalgam filings had mercury vapors in their mouths that were nine times greater than people without the filings. If the person with the amalgam filing chewed, the level of vapor increased six-fold, giving the people with amalgam filings vapor levels that were 54 times greater than those without amalgam filings. The level continued to increase as the people brushed their teeth or after they drank hot beverages. Crinnion described in detail mercury's toxic effects on the brain and the nervous system and the symptoms those effects produce and concluded, "While there is undoubtedly much more to learn about the specific mechanisms of mercury neuro-toxicity, its symptoms are fairly clear."

Dr. Crinnion described the effects of the pollution of Minamata Bay in Japan by methyl mercury and the neurotoxicity suffered by inhabitants of the area that came to be known Minamata Disease: ataxia (lack of normal coordination of voluntary muscles), speech impairment, constriction of visual fields, hypoesthesia (reduced capacity to feel sensation), dysarthria (slurred, slow speech from inability to coordinate mouth muscles), hearing impairment and sensory disturbances. As the mercury contamination spread, these symptoms did also. Forty years after the spill and almost 30 years since a fishing ban was put into effect in the area, problems continued predominantly in the fishing villages. Males complained of stiffness, poor ability to feel sensation, hand tremors, dizziness, loss of pain sensation, cramping, atrophy (wasting away) of upper arm muscles, arthralgia (pain in the joints), insomnia and lumbago (back pain). Females had significantly higher complaints of leg tremors, tinnitus (ringing in the ears or head), loss of touch sensation, atrophy of leg muscles, and muscular weakness.

With regard to the implication of mercury in Alzheimer's disease, Dr. Crinnion cites a 1998 study of cadavers and further studies where very high levels of mercury were found in the brains studied versus the control group; a study where rats were exposed to elemental mercury vapor at the same levels found in mouths of people with amalgams and lesions similar those seen in Alzheimer's disease appeared. He also cites a published case history of a woman suffering from Lou Gehrig's disease (ALS) who had 34 amalgam fillings removed and five months later she was found to have no evidence of motor neuron disorder.

The symptoms of poisoning from inorganic mercury may include nausea and vomiting, abdominal pain, bloody diarrhea, and decreased urination. If inorganic mercury is applied to the skin, the skin may eventually redden or discolor. Skin contact with inorganic mercury can lead to nerve damage. The symptoms of nerve damage are weakness, numbness, and tingling.

The symptoms of poisoning from organic mercury include fatigue, headache, depression, memory problems, hair loss, tremors, and/or a metallic taste in the mouth. These symptoms are also caused by many other common conditions, so organic mercury poisoning can be difficult to diagnose. A person who exhibits these symptoms and also eats a lot of fish might be more quickly suspected to have mercury poisoning.

Diagnosis

Measurement of mercury in the urine is the recommended method of diagnosing metallic and inorganic mercury poisoning. Organic mercury cannot be measured by urinalysis because it does not leave the body in urine. If the urine collection cannot be done over 24 hours, spot urine samples should be collected at the same time each day.

Extent of exposure to organic mercury, including methyl mercury, as well as metallic and inorganic mercury can be measured by a blood test. Unexposed people usually have less than 2 MICROg/100mL of mercury in their blood. Early effects of toxicity are indicated when the blood concentration exceeds 3 MICROg/100 mL.

Treatment

It is worth noting that some herbal and folk treatments for health problems can be a source of mercury. The herbal preparations listed under the "Description" heading above are known to have large concentrations of inorganic mercury. A person prescribed a Chinese herbal ball preparation may want to ask the practitioner about mercury and be alert for symptoms of mercury exposure. Some Mexican skin creams and stomach remedies may also be sources of mercury.

Fish oil supplements are a popular non-prescription treatment used by many people who hope to lower their risk of heart disease, lower their cholesterol, and improve mental function. Because in the United States, the manufacture of nutritional supplements is not regulated like pharmaceuticals are, fish oil supplements may vary greatly from maker to maker and so exposure to organic mercury from fish oil supplements is not readily quantifiable. It makes most sense for a person taking fish oil supplements to determine—if necessary by contacting the manufacturer directly—what kinds of fish are used for the oil, and if mercury levels have been tested for that brand.

Alternative treatment—by a naturopathic physician, a holistic M.D. or osteopathic physician, or a homeopathic practitioner—is based on physical examination, biochemical testing, and an extensive history, including family illness. After evaluating all of this information, treatment may include a comprehensive diet tailored to the individual patient; vitamins, minerals, enzymes, amino acids and or homeopathic remedies tailored to the individual; removal of toxics from patient's environment and diet; removal of amalgam fillings; necessary chiropractic adjustments; counseling; supplementary physical treatment; stress reduction and proper exercise; a stress-free home with help, if needed; a detoxification program; use of a sauna; and chelation, a recognized treatment for heavy metal poisoning, the intra-venous injection of ethylenediamine tetraacetic (EDTA) that will chemically bind the heavy metal and allow it to be removed from the body in the urine.

Allopathic Treatment

A person diagnosed with mercury poisoning may be prescribed a drug that binds the mercury, and thus helps the body excrete it quickly. The body naturally excretes mercury in the urine even without treatment. A doctor may recommend that a person diagnosed with mercury poisoning avoid eating any fish or shellfish. Further monitoring of blood and urine can determine whether mercury levels are falling. The nervous system, mouth, lungs, eyes and skin, target organs for exposure, should also be periodically checked.

Expected Results

For adults, mercury poisoning is usually a reversible problem. The body can rid itself of mercury if the exposure to mercury is halted. Symptoms such as fatigue and memory problems seem to go away as mercury levels fall. However, for children and developing fetuses, mercury poisoning can cause long-term neurological problems. Mercury exposure before birth has been linked to lower intelligence and delays in learning motor skills.

Prevention

Avoiding mercury is the best way to prevent mercury poisoning. Folk remedies that may contain mercury should not be consumed or rubbed on the skin. People should follow local guidelines about eating fish caught in local waters, and should follow federal guidelines for consumption of commercial fish. Much of the scientific literature on long-term exposure to mercury from fish is still mixed. Eating fish has many health benefits, and one reason the FDA revised its fish guidelines several times was that it was afraid to scare people into avoiding fish altogether. In general, larger species of fish are more of a risk for high mercury levels. Canned tuna has less mercury than tuna steaks, because canned tuna comes from smaller fish. For the same reason, light tuna is also generally lower in mercury than white tuna. Common fish and shellfish that are considered low in mercury are shrimp, catfish, pollock, salmon, and light tuna.

Resources

Books

Clark, Hulda Regehr, Ph.D., N.D. The Cure for All Diseases. California: New Century Press, 1995.

Null, Gary, Ph.D. Ultimate Anti-Aging Program. New York: Broadway Books, 1999.

Periodicals

Burros, Marian. "Second Thoughts on Mercury in Fish." New York Times (March 13, 2002): F5.

Crinnion, Walter J, N.D. "Environmental Medicine: Excerpts from Articles on Current Toxicity, Solvents, Pesticides and Heavy Metals." Townsend Letter for Doctors and Patients (January 2001):64.

Gangel, Elaine Kierl. "AAP Report on Mercury in the Environment." American Family Physician (February 2002): 517.

Levine, Samantha. "Who'll Stop the Mercury Rain?" U.S. News & World Report (April 5, 2004): 70.

"Report Warns of Global Threat of Mercury Poisoning." Life Science Weekly (February 24, 2003): 17.

Schardt, David. "Fishing for Mercury: Who's at Risk?" Nutrition Action Healthletter (March 2003): 9.

Stephenson, Joan. "FDA Warns on Mercury in Tuna." Journal of the American Medical Association (January 14, 2004): 171.

Stokstad, Erik. "Uncertain Science Underlies New Mercury Standards." Science (January 2, 2004): 34.

Other

"Mercury and its Many Forms." California Poison Action Line. January 25, 2002 [cited May 10, 2004]. .

"What You Need to Know about Mercury in Fish and Shellfish." U.S. Environmental Protection Agency. March 19, 2004 [cited May 10, 2004]. .

[Article by: Ruth Ann Carter]

 
Columbia Encyclopedia: mercury poisoning
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mercury poisoning, tissue damage resulting from exposure to more than trace amounts of the element mercury or its compounds. Elemental mercury (the silver liquid familiar from thermometers) is the most common occupational source. Exposure typically comes from inhaling mercury vapors. Inorganic salts of mercury (e.g., mercurous chloride, or calomel) are used in some products to inhibit the growth of fungi and bacteria. Organic mercury compounds, especially methylmercury, are more toxic than other forms because they easily cross cell membranes. They are most often ingested in contaminated fish.

Mercury poisoning can cause severe neurological and kidney damage. Acute exposure can affect the respiratory and gastrointestinal systems. Organic mercury can cross the blood-brain barrier and cause irreversible nervous system and brain damage, e.g., loss of motor control, numbness in limbs, blindness, and inability to speak. Some studies have connected maternal mercury exposure to fetal damage. Mercury poisoning can be confirmed by urine tests. Chelation therapy is used for poisoning with elemental mercury and mercury salts; there is no treatment for organic mercury poisoning.

Mercury has become an environmental pollutant in areas where eroding mercury-bearing rock or agricultural and industrial wastes containing the metal escape or are discharged into waterways. Mercury also is released into the atmosphere when coal is burned. Elemental mercury and mercury salts, although fairly inert when deposited on the bottom of waterways, are converted into organic mercury, typically methylmercury, by microorganisms. This compound then enters the food chain where it is biomagnified up to 100,000 times in predacious fish. Consumption of toxic fish and of game birds and mammals that feed on fish is the main risk to humans. Minamata disease was named after the occurrence, in the 1950s and 1960s in Minamata, Japan, of many cases of severe mercury poisoning. It was found that a chemicals factory was discharging mercury-containing wastes into the local waters, contaminating fish that residents caught for food.

Mercury has long been known to be toxic; the phrase "mad as a hatter" refers to the 19th-century occupational disease that resulted from prolonged contact with the mercury used in the manufacture of felt hats. Some workers today, especially laboratory technicians, nurses, and machine operators, continue to be exposed to mercury on the job. Most mercury pesticides have been withdrawn from the U.S. market, and many countries banned ocean dumping of mercury and other pollutants in 1972. Production of mercury-containing interior and exterior paints in the United States was phased out in 1991. Mercury, which has been used in medicines for hundreds of years, continues to be used in dental amalgams and various medicaments that deliver minimal exposures. Most other medical uses have been banned or are being phased out, but mercury use in industry is increasing.

See also water pollution.

Bibliography

See L. Elbert, Mercury Poisoning in Man (1978); P. A. and F. M. D'itri, Mercury Contamination: A Human Tragedy (1988).

Veterinary Dictionary: hydrargyria
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Chronic poisoning from mercury.

Wikipedia: Mercury poisoning
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Mercury poisoning
Classification and external resources

Elemental mercury
ICD-10 T56.1
ICD-9 985.0
DiseasesDB 8057
MedlinePlus 002476
eMedicine emerg/813
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Mercury poisoning (also known as hydrargyria or mercurialism) is a disease caused by exposure to mercury or its compounds. Mercury (chemical symbol Hg) is a heavy metal that occurs in several forms, all of which can produce toxic effects in high enough doses. Its zero oxidation state Hg0 exists as vapor or as liquid metal, its mercurous state Hg+ exists as inorganic salts, and its mercuric state Hg2+ may form either inorganic salts or organomercury compounds; the three groups vary in effects. Toxic effects include damage to the brain, kidney, and lungs.[1] Mercury poisoning can result in several diseases, including acrodynia (pink disease), Hunter-Russell syndrome, and Minamata disease.[2]

Symptoms typically include sensory impairment (vision, hearing, speech), disturbed sensation and a lack of coordination. The type and degree of symptoms exhibited depend upon the individual toxin, the dose, and the method and duration of exposure.

Contents

Signs and symptoms

Common symptoms include peripheral neuropathy (presenting as paresthesia or itching, burning or pain), skin discoloration (pink cheeks, fingertips and toes), edema (swelling), and desquamation (dead skin peels off in layers).

Because mercury blocks the degradation pathway of catecholamines, epinephrine excess causes hyperhidrosis (profuse sweating), tachycardia (persistently faster-than-normal heart beat), mercurial ptyalism (hypersalivation) and hypertension (high blood pressure). Mercury is thought to inactivate S-adenosyl-methionine, which is necessary for catecholamine catabolism by catechol-o-methyl transferase.

Affected children may show red cheeks and nose, erythematous lips (red lips), loss of hair, teeth, and nails, transient rashes, hypotonia (muscle weakness), and photophobia. Other symptoms may include kidney disfunction (e.g. Fanconi syndrome) or neuropsychiatric symptoms (emotional lability, memory impairment, insomnia).

Thus, the clinical presentation may resemble pheochromocytoma or Kawasaki disease.

An example of desquamation of the hand of a child with severe mercury poisoning acquired by handling elemental mercury is this photograph in Horowitz, et al. (2002).[3]

Causes

The consumption of fish is by far the most significant source of ingestion-related mercury exposure in humans, although plants and livestock also contain mercury due to bioaccumulation of mercury from soil, water and atmosphere, and due to biomagnification by ingesting other mercury-containing organisms.[4] Exposure to mercury can occur from breathing contaminated air;[5] from eating foods containing mercury residues from processing, such as can occur with high-fructose corn syrup;[6] from exposure to mercury vapor in mercury amalgam dental restorations;[7] and from improper use or disposal of mercury and mercury-containing objects, for example, after spills of elemental mercury or improper disposal of fluorescent lamps.[8]

Human-generated sources such as coal plants emit approximately half of atmospheric mercury, with natural sources such as volcanoes responsible for the remainder. An estimated two-thirds of human-generated mercury comes from stationary combustion, mostly of coal. Other important human-generated sources include gold production, non-ferrous metal production, cement production, waste disposal, human crematoria, caustic soda production, pig iron and steel production, mercury production (mostly for batteries), and biomass burning.[9]

Mercury and many of its chemical compounds, especially organomercury compounds, can also be readily absorbed through direct contact with bare, or in some cases (such as dimethylmercury) insufficiently protected, skin. Mercury and its compounds are commonly used in chemical laboratories, hospitals, dental clinics, and facilities involved in the production of items such as fluorescent light bulbs, batteries, and explosives.[10]

Mechanism

Mercury is such a highly reactive toxic agent that it is difficult to identify its specific mechanism of damage, and much remains unknown about the mechanism.[11] It damages the central nervous system, endocrine system, kidneys, and other organs, and adversely affects the mouth, gums, and teeth. Exposure over long periods of time or heavy exposure to mercury vapor can result in brain damage and ultimately death. Mercury and its compounds are particularly toxic to fetuses and infants. Women who have been exposed to mercury in pregnancy have sometimes given birth to children with serious birth defects (see Minamata disease).

Mercury exposure in young children can have severe neurological consequences, preventing nerve sheaths from forming properly. Mercury inhibits the formation of myelin.

There is some evidence that mercury poisoning may predispose to Young's syndrome (men with bronchiectasis and low sperm count).[12]

Mercury poisoning's effects partially depend on whether it has been caused by exposure to elemental mercury, inorganic mercury compounds (as salts), or organomercury compounds.

Elemental mercury

Quicksilver (liquid metallic mercury) is poorly absorbed by ingestion and skin contact. It is hazardous due to its potential to release mercury vapour. Animal data indicate that 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. Cases of systemic toxicity from accidental swallowing are rare, and attempted suicide via intravenous injection does not appear to result in systemic toxicity.[11] Though not studied quantitatively, the physical properties of liquid elemental mercury limit its absorption through intact skin and in light of its very low absorption rate from the gastrointestinal tract, skin absorption would not be high.[13] Some mercury vapour is absorbed dermally but uptake by this route is only approximately 1% of that by inhalation.[14]

In humans, approximately 80% of inhaled mercury vapor is absorbed via the respiratory tract where it enters the circulatory system and is distributed throughout the body.[15] Chronic exposure by inhalation, even at low concentrations in the range 0.7–42 μg/m3, has been shown in case control studies to cause effects such as tremors, impaired cognitive skills, and sleep disturbance in workers.[16][17]

Inorganic mercury compounds

Mercury occurs inorganically as salts such as mercury(II) chloride. Mercury salts primarily affect the gastro-intestinal tract and the kidneys, and can cause severe kidney damage; however, as they can not cross the blood-brain barrier easily, mercury salts inflict little neurological damage without continuous or heavy exposure.[18] As two oxidation states of mercury form salts (Hg+ and Hg2+), mercury salts occur in both mercury(I) (or mercurous) and mercury(II) (mercuric) forms. Mercury(II) salts are usually more toxic than their mercury(I) counterparts because their solubility in water is greater; thus, they are more readily absorbed from the gastrointestinal tract.[18]

Hg(CN)2 is a particularly toxic mercury compound. If ingested, both life-threatening mercury and cyanide poisoning can occur. Hg(CN)2 can enter the body via inhalation, ingestion, or passage through the skin. Inhalation of mercuric cyanide irritates the throat and air passages. Heating or contact of Hg(CN)2 with acid or acid mist releases toxic mercury and cyanide vapors that can cause bronchitis with cough and phlegm and/or lung tissue irritation. Contact with eyes can cause burns and brown stains in the eyes, and long time exposure can affect the peripheral vision. Contact with skin can cause skin allergy, irritation, and gray skin color.[19]

Chronic exposure to trace amounts of the compound can lead to mercury buildup in the body over time; it may take months or even years for the body to eliminate excess mercury. Overexposure to mercuric cyanide can lead to kidney damage and/or mercury poisoning, leading to 'shakes' (ex: shaky handwriting), irritability, sore gums, increased saliva, metallic taste, loss of appetite, memory loss, personality changes, and brain damage. Exposure to large doses at one time can lead to sudden death.[19]

Mercuric cyanide has not been tested on its ability to cause reproductive damage. Although inorganic mercury compounds (such as Hg(CN)2) have not been shown to be human teratogens, they should be handled with care as they are known to damage developing embryos and decrease fertility in men and women.[19]

According to one study, two people exhibited symptoms of cyanide poisoning within hours after ingesting mercuric cyanide or mercury oxycyanide, Hg(CN)2•HgO, in suicide attempts. The toxicity of Hg(CN)2 is commonly assumed to arise almost exclusively from mercury poisoning; however, the patient who ingested mercury oxycyanide died after 5 hours of cyanide poisoning before any mercury poisoning symptoms were observed. The patient who ingested Hg(CN)2 initially showed symptoms of acute cyanide poisoning which were brought under control, and later showed signs of mercury poisoning before recovering. It is thought that the degree to which cyanide poisoning occurs is related to whether cyanide ions are released in the stomach, which depends on factors such as the amount ingested, stomach acidity, and volume of stomach contents.[20] Given that Hg(CN)2 molecules remain undissociated in pure water and in basic solutions,[21] it makes sense that dissociation would increase with increasing acidity. High stomach acidity thus helps cyanide ions to become more bioavailable, increasing the likelihood of cyanide poisoning.

Mercury cyanide was used in two murders in New York in 1898. The perpetrator, Roland B. Molineux, sent poisoned medicines to his victims through the US mail. The first victim, Henry Barnett, died of mercury poisoning twelve days after taking the poison. The second victim, Catherine Adams, died of cyanide poisoning within 30 minutes of taking the poison. As in the suicide cases, the difference between the two cases may be attributed to differences in the acidities of the solutions containing the poison, or to differences in the acidities of the victims' stomachs.[22]

The drug NAP (n-acetyl penicillamine) has been used to treat mercury poisoning with limited success.[19]

Organic mercury compounds

Compounds of mercury tend to be much more toxic than the element itself, and organic compounds of mercury are often extremely toxic and have been implicated in causing brain and liver damage. The most dangerous mercury compound, dimethylmercury, is so toxic that even a few microliters spilled on the skin, or even a latex glove, can cause death.[23][24]

Methylmercury is the major source of organic mercury for all individuals.[1] It works its way up the food chain through bioaccumulation in the environment, reaching high concentrations among populations of some species. Larger species of fish, such as tuna or swordfish, are usually of greater concern than smaller species. The U.S. Food and Drug Administration (FDA) and the U.S. Environmental Protection Agency (EPA) advise women of child-bearing age, nursing mothers, and young children to completely avoid swordfish, shark, king mackerel and tilefish (golden bass), to limit consumption of albacore ("white") tuna to no more than 6 oz (170 g) per week, and of all other fish and shellfish to no more than 12 oz (340 g) per week.[25] A 2006 review of the risks and benefits of fish consumption found that for adults the benefits of one to two servings of fish per week outweigh the risks, even (except for a few fish species) for women of childbearing age, and that avoidance of fish consumption could result in significant excess coronary heart disease deaths and suboptimal neural development in children.[26]

There is a long latent period between exposure to methylmercury and the appearance of symptoms in adult poisoning cases. The longest recorded latent period is five months after a single exposure, in the Dartmouth case (see History); other latent periods in the range of weeks to months have also been reported. No explanation for this long latent period is known. When the first symptom appears, typically paresthesia (a tingling or numbness in the skin), it is followed rapidly by more severe effects, sometimes ending in coma and death. The toxic damage appears to be determined by the peak value of mercury, not the length of the exposure.[11]

Ethylmercury is a breakdown product of the antibacteriological agent ethylmercurithiosalicylate, which has been used as a topical antiseptic and a vaccine preservative (further discussed under Thiomersal below). Its characteristics have not been studied as extensively as those of methylmercury. It is cleared from the blood much more rapidly, with a half-life of 7 to 10 days, and it is metabolized much more quickly than methylmercury. It probably does not have methylmercury's ability to cross the blood-brain barrier via a transporter, but instead relies on simple diffusion to enter the brain.[1]

Other exposure sources of organic mercury include phenylmercuric acetate and phenylmercuric nitrate. These were used in indoor latex paints for their anti-mildew properties, but were removed in 1990 because of cases of toxicity.[1]

Diagnosis

Diagnosis of elemental or inorganic mercury poisoning involves determining the history of exposure, physical findings, and an elevated body burden of mercury. Although whole blood mercury concentrations are typically less than 6 μg/L, diets rich in fish can result in blood mercury concentrations higher than 200 μg/L; it is not that useful to measure these levels for suspected cases of elemental or inorganic poisoning because of mercury's short half-life in the blood. If the exposure is chronic, urine levels can be obtained; 24-hour collections are more reliable than spot collections. It is difficult or impossible to interpret urine samples of patients undergoing chelation therapy, as the therapy itself increases mercury levels in the samples.[27]

Diagnosis of organic mercury poisoning differs in that whole-blood or hair analysis is more reliable than urinary mercury levels.[27]

Prevention

Mercury poisoning can be prevented (or minimized) by eliminating or reducing exposure to mercury and mercury compounds. To that end, many governments and private groups have made efforts to regulate the use of mercury heavily, or to issue advisories about its use. For example, the export from the European Union of mercury and some mercury compounds will be prohibited from 2011-03-15.[28] The variability among regulations and advisories is at times confusing for the lay person as well as scientists.

[29]
Country Regulating agency Regulated activity Medium Type of mercury compound Type of limit Limit
US Occupational Safety and Health Administration occupational exposure air elemental mercury Ceiling (not to exceed) 0.1 mg/m³
US Occupational Safety and Health Administration occupational exposure air organic mercury Ceiling (not to exceed) 0.05 mg/m³
US Food and Drug Administration drinking water inorganic mercury Maximum allowable concentration 2 ppb (0.002 mg/L)
US Food and Drug Administration eating sea food methylmercury Maximum allowable concentration 1 ppm
US Environmental Protection Agency drinking water inorganic mercury Maximum contaminant level 2 ppb (0.002 mg/L)

The United States Environmental Protection Agency‎ (EPA) issued recommendations in 2004 regarding exposure to mercury in fish and shellfish. [30] The EPA also developed the "Fish Kids" awareness campaign for children and young adults [31] on account of the greater impact of mercury exposure to that population.

Treatment

Identifying and removing the source of the mercury is crucial. Decontamination requires removal of clothes, washing skin with soap and water, and flushing the eyes with saline solution as needed. Inorganic ingestion such as mercuric chloride should be approached as the ingestion of any other serious caustic. Immediate chelation therapy is the standard of care for a patient showing symptoms of severe mercury poisoning or the laboratory evidence of a large total mercury load.[1]

Chelation therapy for acute inorganic mercury poisoning can be done with DMSA, 2,3-dimercapto-1-propanesulfonic acid (DMPS), D-penicillamine (DPCN), or dimercaprol (BAL).[1] Only DMSA is FDA-approved for use in children for treating mercury poisoning. However, several studies found no clear clinical benefit from DMSA treatment for poisoning due to mercury vapor.[32] No chelator for methylmercury or ethylmercury is approved by the FDA; DMSA is the most frequently used for severe methylmercury poisoning, as it is given orally, has fewer side effects, and has been found to be superior to BAL, DPCN, and DMPS.[1] Alpha-lipoic acid (ALA) has been shown to be protective against acute mercury poisoning in several mammalian species when it is given soon after exposure; correct dosage is required, as inappropriate dosages increase toxicity. Although it has been hypothesized that frequent low dosages of ALA may have potential as a mercury chelator, studies in rats have been contradictory.[33] Glutathione and N-acetylcysteine (NAC) are recommended by some physicians, but have been shown to increase mercury concentrations in the kidneys and the brain.[33] Experimental findings have demonstrated an interaction between selenium and methylmercury, but epidemiological studies have found little evidence that selenium helps to protect against the adverse effects of methylmercury.[34]

Even if the patient has no symptoms or documented history of mercury exposure, a minority of physicians (predominantly those in alternative medicine) use chelation to "rid" the body of mercury, which they believe to cause neurological and other disorders. A common practice is to challenge the patient's body with a chelation agent, collect urine samples, and then use laboratory reports to diagnose the patient with toxic levels of mercury; often no pre-chelation urine sample is collected for comparison. The patient is then advised to undergo further chelation.[32] No scientific data supports the claim that the mercury in vaccines causes autism[35] or its symptoms,[36] and there is no scientific support for chelation therapy as a treatment for autism.[37]

Chelation therapy can be hazardous. In August 2005, an incorrect form of EDTA used for chelation therapy resulted in hypocalcemia, causing cardiac arrest that killed a five-year-old autistic boy.[38]

Prognosis

Many of the toxic effects of mercury are partially or wholly reversible, either through specific therapy or through natural elimination of the metal after exposure has been discontinued.[39] However, heavy or prolonged exposure can do irreversible damage, particularly in fetuses, infants, and young children. Young's syndrome is believed to be a long term consequence of early childhood mercury poisoning.[40]

History

  • The first emperor of unified China, Qin Shi Huang, reportedly died of ingesting mercury pills that were intended to give him eternal life.[41]
  • The phrase mad as a hatter is likely a reference to mercury poisoning, as mercury-based compounds were once used in the manufacture of felt hats in the 18th and 19th century. (The Mad Hatter character of Alice in Wonderland was almost certainly inspired by an eccentric furniture dealer, not by a victim of mercury poisoning.)[42]
  • 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 vapour 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. He published a number of papers on mercury poisoning, founded a committee in Berlin to study cases of possible mercury poisoning, and introduced the term micromercurialism.[43]
  • 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.[44]
  • 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 due to what became known as Minamata disease. 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.[2]
  • 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 (see Basra poison grain disaster).[45]
  • On August 14, 1996, Karen Wetterhahn, a chemistry professor working at Dartmouth College, 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.[23][24]
  • In April 2000, Alan Chmurny attempted to kill a former employee, Marta Bradley, by pouring mercury into the ventilation system of her car.[46]
  • On March 19, 2008, Tony Winnett, 55, inhaled mercury vapors while trying to extract gold from computer parts, and died ten days later. His Oklahoma residence became so contaminated that it had to be gutted.[47][48]
  • In December 2008, actor Jeremy Piven was diagnosed with hydrargyria resulting from eating sushi twice a day for twenty years.[49]

Acrodynia

Acrodynia (also known as "calomel disease," "erythredemic polyneuropathy," and "pink disease") is a type of mercury poisoning in children characterized by pain and pink discoloration of the hands and feet.[50] The word is derived from the Greek, where ακρος means high (as in: upper extremity) and οδυνη means pain. Also known as pink disease, erythredema, Selter's disease, or Swift-Feer disease, acrodynia was relatively commonplace amongst children in the first half of the 20th century.[51] Initially, 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.[51] The prevalence of acrodynia decreased greatly after calomel was excluded from most teething powders in 1954.[51]

Medical procedures

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Because elemental mercury often passes through the GI tract without being absorbed, it was used medically for various purposes until the dangers of mercury poisoning became known. For example, elemental mercury was used to mechanically clear intestinal obstructions (due to its great weight and fluidity), and it was a key ingredient in various medicines throughout history, such as blue mass. 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. While the usage of mercury in medicine has declined, mercury-containing compounds are still used medically in vaccines and dental amalgam, both of which have been the subject of controversy regarding their potential for mercury poisoning.

Thiomersal

For more details on this topic, see Thiomersal controversy.

The mercury-based preservative thiomersal (commonly called thimerosal in the U.S.) has been added to vaccines since the 1930s to prevent their deterioration.[11] Its use in vaccines has been hypothesized as a cause of autistic behaviors.[52] This hypothesis is controversial, as much evidence suggests that the cause of autism is about 90% genetic.[53] The hypothesis has not been confirmed by reliable studies.[54] However, organizations such as the American Academy of Pediatrics have recommended that the use of thiomersal be reduced as a precautionary measure. With the exception of some flu vaccines, it is no longer used as a preservative in routinely recommended childhood vaccines in the United States; it is still in limited use as a preservative in multi-dose flu and tetanus vaccines and a few other non-childhood vaccines.[55]

Dental amalgam

For more details on this topic, see Dental amalgam controversy.

Dental amalgam, an alloy of about 50% elemental mercury, was first introduced in France in the early 1800s[56] Although this amalgam is a source of low-level exposure to mercury, no scientific evidence links it as a cause of clinically significant toxic effects, except for the rare local hypersensitivity reaction. The National Institutes of Health has stated that amalgam fillings pose no personal health risk, and that replacement by non-amalgam fillings is not indicated.[1]

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.[57] The use of mercury in cosmetics is illegal in the United States. However, cosmetics containing mercury are often illegally imported. Following a certified case of mercury poisoning resulting from the use of an imported skin whitening product, the United States Food and Drug Administration warned against the use of such products.[58][59] Symptoms of mercury poisoning have resulted from the use of various mercury-containing cosmetic products.[11][60][61] The use of skin whitening products is especially popular amongst Asian women.[62] In Hong Kong in 2002, two products were discovered to contain between 9,000 to 60,000 times the recommended dose.[63]

Fluorescent lamps

Fluorescent lamps contain mercury which is 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.[64] When broken indoors, bulbs may emit sufficient mercury vapor to present health concerns, and the U.S. Environmental Protection Agency recommends evacuating and airing out a room for at least 15 minutes after breaking a fluorescent light bulb.[65] Breakage of multiple bulbs presents a greater concern. 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 case of acrodynia 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. The glass was cleaned up and discarded, but the child often used the area for play.[66]

See also

References

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External links

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Poisonous plants/
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Britannica Concise Encyclopedia. Britannica Concise Encyclopedia. © 2006 Encyclopædia Britannica, Inc. All rights reserved.  Read more
Dental Dictionary. Mosby's Dental Dictionary. Copyright © 2004 by Elsevier, Inc. All rights reserved.  Read more
Alternative Medicine Encyclopedia. Encyclopedia of Alternative Medicine. Copyright © 2005 by The Gale Group, Inc. All rights reserved.  Read more
Columbia Encyclopedia. The Columbia Electronic Encyclopedia, Sixth Edition Copyright © 2003, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/.  Read more
Veterinary Dictionary. Saunders Comprehensive Veterinary Dictionary 3rd Edition. Copyright © 2007 by D.C. Blood, V.P. Studdert and C.C. Gay, Elsevier. All rights reserved.  Read more
Wikipedia. This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article "Mercury poisoning".  Read more