| Resources | Healthy Child Healthy World

Description

Mercury is a toxic heavy metal that is found naturally in the environment. As the result of human activities, environmental levels have increased substantially over natural levels. Mercury is found in three forms: organic, inorganic and elemental (mercury).

Mercury is a potent neurotoxin that can cause permanent damage to the brain and central nervous system, especially among young children. In pregnant women, mercury can pass through the placenta and can harm the fetus.

The most common organic form of mercury (when it is combined with carbon) is methylmercury, which accumulates in the flesh of fish, animals and humans. It is produced when microorganisms, such as bacteria, in water and soil convert elemental mercury into methylmercury. Methylmercury is a common contaminant of fish and seafood. It rises up the food chain and reaches its highest levels in predatory species, such as shark and tuna, and bottom-feeders, such as crab.

The elemental or “pure” form (when it is not combined with other elements) is a shiny, silver-white, liquid metal that beads. This characteristic makes it attractive to children who may be tempted to play with it. At room temperature, it also evaporates into mercury vapors. Elemental mercury is used in thermometers, electrical switches, fluorescent lights, thermostats, barometers, batteries, dental fillings, and other products. It is also still used in some Latin American and Asian herbal or religious remedies, and in some rituals or spiritual practices in some Latin American and Caribbean religions such as Voodoo, Santeria and Espiritismo. Approximately 80 percent of the mercury released into the environment as a result of human activities is elemental mercury, primarily from fossil fuel combustion in power plants, mining, smelting, and solid waste incineration. High doses of elemental mercury in a short time period are the most dangerous.

Inorganic mercury is mercury combined with elements such as chlorine, oxygen or sulfur. Mercuric chloride, or the more toxic mercurous chloride are examples. Most inorganic mercury is in the form of powders or crystals. Inorganic mercury compounds are or have been used in the past in a variety of products including pigments (such as tattoo dyes), vaccines, medicines (as a preservative, for example), skin bleaching creams, disinfectants or antiseptics, paints and pesticides. Phenylmercuric compounds were banned from interior and exterior paints in 1991 due to risks from the mercury vapors. Inorganic mercury causes damage to kidneys.

Natural forms of mercury in the environment come from volcanoes, hot springs, and from the breakdown of minerals in rocks.

Toxicity information varies by form.

Health Effects

Immediate Health Effects

If SWALLOWED, mercury is Not Available
If ABSORBED THROUGH SKIN, mercury is Not Available
If INHALED (SNIFFED OR BREATHED IN), mercury is Not Available

Longterm or Delayed Health Effects

Allergen
Neurotoxin = Can harm brain and central nervous system
Suspected Endocrine Disruptor = May interfere with, mimic or block hormones
Development Toxicant = Can interfere with normal development of a fetus or child
Reproductive Toxicant = Can harm reproductive system

Other

Harm to developing fetus. Children of women exposed to high levels of methylmercury during or before pregnancy have exhibited delayed onset of walking and talking, brain damage, mental retardation, blindness, seizures, inability to speak, cerebral palsy, altered muscle tone, deep tendon reflexes.

Children exposed to far lower methylmercury exposures in the womb have exhibited delays and deficits in learning ability that may not be apparent except by the use of very sensitive neuropsychological tests.

Animals exposed orally to long-term, high levels of methylmercury or phenylmercury in laboratory studies experienced adverse effects on the developing fetus, sperm, and male reproductive organs; and increases in the number of spontaneous abortions and stillbirths.

In critical periods of development before they are born, and in the early months after birth, children and fetuses are particularly sensitive to the harmful effects of metallic mercury and methylmercury on the nervous system.
There is little information on the effects in humans from long-term, low-level exposure to inorganic mercury. Children treated with mercurous chloride for constipation, worms, or teething discomfort also have had swollen red gums, excessive salivation, weight loss, diarrhea and/or abdominal pain, and muscle twitching or cramping in the legs and/or arms. Kidney damage is very common after exposure to toxic levels of inorganic mercury. Metallic mercury or methylmercury that enters the body can also be converted to inorganic mercury and result in kidney damage.
At high doses, both organic and elemental mercury can cause permanent brain and central nervous system damage, particularly to the developing brains of fetuses, infants, and small children; permanent kidney damage; or death.

Different forms of mercury affect the nervous system differently. The nervous system is more sensitive to methylmercury toxicity than are other organs in the body. Evidence suggests that the effects worsen with age, even after the exposure stops.

Organic and elemental mercury exposure can also cause tremors, muscle incoordination (i.e., inability to walk), personality changes (such as irritability, excessive shyness, confidence loss, nervousness), loss of sensation, changes in vision or hearing, memory loss and deficits in cognitive function. Mercury exposure may also be associated with behavioral problems, and with peripheral neuropathy, the failure of the nerves that carry information between the brain and spinal cord, leading to pain, loss of sensation, and inability to control muscles. Children prenatally exposed to mercury may also be maintain less normal heart rate variability, a risk factor for developing heart disease.
If ingested at high levels, inorganic mercury can cause kidney damage, vomiting, nausea, severe ulcers, abdominal pain and diarrhea. Effects on the heart have also been observed in children after they accidentally swallowed mercuric chloride. Symptoms included rapid heart rate and increased blood pressure.
If inhaled at high levels over a short time, elemental mercury can damage the lining of the mouth and irritate the lungs and airways, causing tightness of the chest, a burning sensation in the lungs, and coughing. Other effects from exposure to mercury vapor include nausea, vomiting, diarrhea, increases in blood pressure or heart rate, skin rashes, and eye irritation.

Elemental mercury vapors may also cause acrodynia or “pink disease,” which causes leg cramps, irritability, and abnormal redness of the skin, leading to peeling palms of hands and soles of feet. Excessive perspiration, itching, rash, joint pain and weakness, fretfulness, sleeplessness, elevated blood pressure and rapid heart rate may also be present.
Elemental mercury is not as toxic when ingested compared to when it is inhaled--except in very large amounts.

Skin contact with elemental mercury has been shown to cause an allergic reaction (skin rashes) in some people, but otherwise is not as toxic as inhalation.
Possible cancer risk. The World Health Organization has classified methylmercury as a possible human carcinogen but has found metallic and inorganic mercury to be unclassifiable as to carcinogenicity. Methylmercury exposure may have been linked to liver and esophagus cancers in overexposed populations in Minamata, Japan. Mercuric chloride and methylmercury have caused tumors in test animals.

How Exposures Occur

Fish and Seafood

Fish and seafood are the main source of methylmercury in the diet, containing approximately 1,000 to 10,000 times more methylmercury than other foods. Saltwater fish (especially sharks and swordfish) that live a long time and can grow to a very large size, and marine mammals such as whales, seals, dolphins and walruses tend to have the highest levels of mercury in their bodies. Children may be exposed to methylmercury when they eat contaminated fish and seafood, or when these foods are eaten by their mother during pregnancy.

Both inorganic and methylmercury will pass into breast milk and into the fetus from a pregnant women if they enter a nursing or pregnant woman’s body. However, the benefits of breast feeding are generally greater than the possible adverse effects of mercury in breast milk.

Young children and women who are pregnant (or may be in the future) or nursing should avoid consuming fish under mercury advisory.

The U.S. Environmental Protection Agency also recommends that women who are pregnant or may become pregnant, nursing mothers and young children, limit consumption of fish from non-commercial sources — freshwater fish both caught and directly eaten by subsistence and recreational fishers — to one meal per week (six ounces of cooked fish per adult; two ounces of cooked fish per child). In addition, they should not eat commercially-available shark, swordfish, king mackerel, or tilefish, which are highest in mercury, the U.S. Food and Drug Administration has warned.

Environmental Working Group recommends going a step further and avoiding these other high-mercury seafoods as well: tuna steaks, sea bass, oysters (from the Gulf of Mexico), marlin, halibut, and white croaker. They recommend restricting consumption of canned tuna to only once a month as a precaution.

For CHEC’s own fish consumptions recommendations, see our Safe Fish CHEC List for Children, Teens and All Women of Child-bearing Age.

Amalgam Dental Fillings

Metal amalgam, or “silver” dental fillings are generally about 50 percent mercury. Exposure may occur during the dental procedure or as the result of corrosion or chewing or grinding motions that may slowly release very small amounts of mercury either as a vapor or dissolved in saliva.

The mercury from dental amalgam may contribute as much as 75% of your total daily mercury exposure, depending on the number of amalgam fillings you have, the amount of fish consumed and the levels in the fish, etc. Whether the level of exposure could cause harm is an ongoing subject of debate and research by scientists and health officials.

According to the U.S. Agency for Toxic Substances and Disease Registry (ATSDR), U.S. government summaries on the effects of dental amalgam conclude that there is no apparent health hazard to the general population. However, they also recommend further study to determine the possibility of more subtle behavioral or immune system effects as well as the levels of exposure that may result in adverse effects in sensitive populations, including pregnant women, children under the age of 6 (especially up to the age of 3), people with impaired kidney function, and people with hypersensitive immune responses to metals.

If you or your children among this group, you should discuss this with your dentist prior to any dental restoration work. Removal of dental amalgams in people who have no indication of adverse effects is not recommended and can put the person at greater risk, if performed improperly. Chelation therapy (used to remove metals from the body tissues) itself presents some health risks, and should be considered only when a licensed occupational or environmental health physician determines it necessary to reduce immediate and significant health risks due to high levels of mercury in the body.

The American Dental Association, the U.S. Food and Drug Administration and others have reviewed the research and have concluded that dental amalgam is a safe way to repair teeth.

Caribbean Religious Rituals

Children can inhale mercury vapors when metallic mercury, or “azogue,” is used in rituals and spiritual practices of LatinAmerican a nd Caribbean religions such as Santeria, Voodoo, Espiritismo and Palo Mayombe. Azogue can be purchased in “botanica” stores in capsules or in glass containers. It is sometimes placed in a sealed pouch to be worn on a necklace or in a pocket, or it may be sprinkled in the home or car. Some people may mix azogue in bath water or perfume, or place azogue in devotional candles.

In all cases, this use will release mercury vapors into the surrounding air and can continue to result in exposures for months or years after the ceremony is finished.

Thermometers and Other Consumer Products

Children may be exposed to mercury from some consumer products, such as glass thermometers, electrical switches, fluorescent and high intensity light bulbs, blood pressure manometers, thermostats, computers and electronic equipment. In most cases, the mercury is contained and should not pose a risk unless damaged or broken, in which case mercury vapors or metallic mercury beads may be released.

Metallic mercury and its vapors are extremely difficult to remove from clothes, furniture, carpet, floors, walls, and other such items. If these items are not properly cleaned, the mercury can remain for months or years and continue to be a source of exposure.

Children can also be exposed to mercury by swallowing or applying to their skin outdated medicinal products (laxatives, worming medications, and teething powders) that contain mercurous chloride. Exposure may also occur from the improper or excessive use of other chemicals containing mercury, such as skin-lightening creams and some topical antiseptic or disinfectant agents (mercurochrome and thimerosal).

Musical greeting cards, talking refrigerator magnets, lighted athletic shoes (sneakers), and electronic toys could also contain mercury. These are not likely to pose a risk during use although they contribute to contamination of the environment when disposed.

Outdoor Exposures

Children can inhale small amounts of mercury from polluted air from coal-fired power plants, spills, municipal and medical waste incinerators, metal mines, cement factories or hazardous waste sites. Most outdoor air is not likely to contain levels that would be harmful.

Exposure to mercury compounds at hazardous waste sites is much more likely to occur from handling contaminated soil (i.e., children playing in or eating contaminated surface soil), drinking well-water, or eating fish from contaminated waters near those sites. Some forms of organic mercury can be absorbed through the skin.

Vaccines and Other Medicines

A few vaccines and other medicines contain small amounts of mercury compounds, such as thimerosal (which contains ethyl mercury), phenylmercuric acetate, and phenylmercuric nitrate.

When vaccines containing thimerosal have been administered in the recommended doses, only minor effects such as swelling or redness at the injection site have been noted, but no other harmful effects have been reported. However, to be on the safe side, in July 1999, the Public Health Service agencies (PHS), the American Academy of Pediatrics (AAP), and vaccine manufacturers agreed that thimerosal levels in vaccines should be reduced or eliminated. The U.S. Food and Drug Administration (FDA) committed to expediting the review of new vaccines that do not contain thimerosal.

Currently, all routinely recommended pediatric vaccines that are manufactured for the U.S. market contain no thimerosal or contain only trace amounts of it. These include: MMR (measles, mumps, rubella), varicella (chickenpox), inactivated polio (IPV), and pneumococcal conjugate vaccines.

Some traditional Chinese and Hispanic and homeopathic remedies for stomach disorders (for example, herbal balls) contain mercury and may harm children if ingested directly, or if used by pregnant or nursing mothers, who can pass on mercury to their unborn child or nursing infant.

Some skin-lightening creams may contain ammoniated mercuric chloride and mercuric iodide.

Significant Statistics

In the United States, over 60,000 children each year may be born at risk for neurodevelopmental effects because of exposure to methylmercury in utero, the National Academy of Sciences estimates.

National Research Council. Toxicological Effects of Methylmercury. Washington, D.C.: National Academy Press, 2000.http://books.nap.edu/books/0309071402/html/325.html

Dentists are the third largest users of mercury in the U.S., using approximately 40 metric tons of mercury each year in silver amalgam fillings, which are 50% mercury. Dentist offices are the largest source of mercury pollution to the nation’s wastewater treatment plants.

Dentist the Menace? The Uncontrolled Release of Dental Mercury. Mercury Policy Project, Health Care Without Harm, Sierra Club, et al., June 2002.

http://www.mercurypolicy.org/new/documents/DentistTheMenace.pdf

As of December 2000, 41 states had issued *2,242* advisories limiting fish consumption from local lakes, rivers or coastal areas due to mercury contamination. Almost 79 percent of all advisories issued in the U.S. are a result of mercury contamination in fish and shellfish. Advisories for mercury have increased steadily, from 899 advisories in 1993 to 2,242 advisories in 2000. The number of states that have issued mercury advisories also has risen steadily from 27 states in 1993 to 41 states in 2000.

Mercury Update: Impact on Fish Advisories. U.S. Environmental Protection Agency, Office of Water, June 2001.http://www.epa.gov/waterscience/fish/chemfacts.html

Methylmercury levels in predator fish are approximately 1-10 million times higher than methylmercury concentrations in surrounding waters.

Mercury Update: Impact on Fish Advisories. U.S. Environmental Protection Agency, Office of Water, June 2001.http://www.epa.gov/waterscience/fish/chemfacts.html

Approximately 10 percent (6 million) of U.S. women have mercury levels within one-tenth of potentially hazardous levels, indicating a narrow margin of safety.

U.S. Food and Drug Administration, U.S. Environmental Protection Agency, et al. “Blood and Hair Mercury Levels in Young Children and Women of Childbearing Age--United States, 1999.” Morbidity and Mortality Weekly, Vol. 50, No.8 (March 2, 2001), pp. 140-3.http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5008a2.htm

Approximately 60 percent of the mercury deposition that occurs in the United States comes from domestic, human-made sources of pollution.

Mercury Study Report to Congress. U.S. Environmental Protection Agency, December 1997.

http://www.epa.gov/airprogm/oar/mercury.html

Solutions

How to detect mercury

The largest fish, especially predator fish at the top of the food chain, will have the highest methylmercury levels. These include shark, swordfish, tuna, mackerel, sea bass, marlin, halibut and tilefish. See our Fish Toxins chart (PDF) for more on mercury and fish. For more information on which fish contain the highest mercury levels, see the Safe Fish CHEC List for Children, Teens and All Women of Child-bearing Age.

Check local fish advisories before consuming fish from local fresh or ocean waters. Your state health department can tell you if any fish consumption advisories exist in your area, or you can check our State Fish Consumption Advisory Links.
Check labels on medicines such as antiseptics, eye drops, eye ointments, nasal sprays, skin-lightening creams, and herbal preparations. Avoid or minimize unnecessary use of these products containing any form of mercury, including mercurochrome, thimerosal (also called merthiolate), mercuric chloride, ammoniated mercuric chloride, mercuric acetate, mercuric nitrate, and mercuric iodide.

How to minimize exposure to mercury

If a thermometer breaks and spills mercury in your home:

1) Avoid touching it or breathing its fumes. Ask others, particularly children, to leave the area.

2) Open windows and doors to ventilate the area during cleanup.

3) Clean up the mercury beads by using one sheet of paper to carefully roll them onto a second sheet of paper, or by sucking very small beads of mercury into an eye dropper. Place mercury, paper, and eye dropper into a plastic bag or airtight container. Do not use a vacuum cleaner to clean up mercury, as this will spread mercury vapors into the air (from the vacuum’s exhaust). Do not try to wipe or blot it up with a cloth or paper towel, as this will only spread the mercury and break it up into smaller beads, making it more difficult to remove. If mercury spills on carpet, try to remove beads with the same method, but call a poison control center for further advice on cleanup.

4) Remove it from your house, then contact the local poison control center, fire department, or public health board for advice on proper disposal.

Metallic mercury and its vapors are extremely difficult to remove from clothes, furniture, carpet, floors, walls, and other such items. If these items are not properly cleaned, the mercury can remain for months or years, and continue to be a source of exposure.

If you accidently touch metallic mercury or it gets on your clothing, wash yourself thoroughly and discard contaminated clothing by placing them in a sealed plastic bag.
Be sure to properly dispose of mercury-containing household items such as thermometers and fluorescent light bulbs. Call your local sanitation department to find out how to dispose of these and other household hazardous waste, or find this information at Earth 911.

When possible, recycle old computers and electrical equipment, which often contain mercury in switches. See Conscientious Computing: What to Do With Your Old Computer.
Removal of dental amalgams in people who have no indication of adverse effects is not recommended and can put the person at greater risk, if performed improperly.

Alternatives

Fish that are lower on the food chain generally contain the least mercury contamination. Fish and seafood that have consistently tested lowest for mercury are anchovy, catfish, clams; cod, flounder, sole and pollock from the Pacific only; herring, farmed oysters, ocean perch, sardines, scallops, shrimp, tilapia, trout. For more detailed information, see Fish and Seafood: Charting a Course for the Safest Choices.

Note: Because mercury concentrates in the muscle tissue of fish, skinning, trimming, or cooking the fish will not significantly reduce mercury levels in contaminated fish.
Switch to digital thermometers, which give accurate readings and contain no mercury. Mercury-free cooking thermometers that are not digital (such as those that are alcohol-based) are also available, but you may have to call a manufacturer to find out which models are made without mercury.
White plastic/glass composite resins are a mercury-free alternative to amalgam dental fillings. However, these are often slightly more expensive than metal amalgam fillings and may contain the hormone disrupting chemical, bisphenol-A. Discuss the best option with your dentist.

For More information

Books, articles, factsheets and reports

Brain Food: What Women Should Know About Mercury Contamination of Fish. Environmental Working Group, 2001.

http://www.ewg.org/reports/BrainFood/pr.html

What You Need to Know About Mercury: What to Do if Mercury Spills. U.S. Environmental Protection Agency, SuperFund Kids Page, Updated October 1, 1998.

http://www.epa.gov/oerrpage/superfund/kids/sup_fact/mercury3.htm

Dentist the Menace? The Uncontrolled Release of Dental Mercury. Mercury Policy Project, Health Care Without Harm, Sierra Club, et al., June 2002.

http://www.mercurypolicy.org/new/documents/DentistTheMenace.pdf