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, kidneys 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 inorganic 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. Most of the mercury released into the environment as a result of human activities is elemental and inorganic 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. Mercury can result in increased risk of miscarriage and increased incidents of birth defects including vision problems and impaired organ systems.  Studies have shown that prenatal exposure to mercury can result in poorer performance on neuropsychologcal tests during childhood.
 
• 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.
 
• 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. Exposure can also result in irritability, shyness, tremors, changes in vision or hearing, and memory problems.
 
• 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 less normal heart rate variability, a risk factor for developing heart disease.
 
• If ingested at high levels, inorganic mercury can cause kidney and lung damage, vomiting, nausea, severe ulcers, abdominal pain, skin rashes, eye irritation 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 . cause tremors, mood swings, irritability, nervousness, excessive shyness, insomnia, such as weakness, muscle atrophy, twitching, headaches, disturbances in sensations, changes in nerve responses and poor performance on cognitive function tests. At higher exposures there may be kidney effects, respiratory failure and death.
 
• 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.
 
• Possible cancer risk. There is no direct evidence of cancer in humans, but 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 and young children, limit consumption of fish to 12 oz per week of low-mercury fish, less for children. 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.  Monitor local advisories for waters if you fish in them, and consume up to 6 oz per week of fish from local waters if there is no information from local authorities on them.

Environmental Working Group recommends pregnant women go a step further and avoid these other high-mercury seafoods as well: shark, swordfish, king mackerel, tilefish, tuna steaks, canned tuna, sea bass, gulf coast, oysters, marlin, halibut, pike, walleye, white croaker and largemouth bass.

For Health Child, Healthy World’s own fish consumptions recommendations, see our Safe Fish Checklist 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.
   
    There are currently some alternatives for filling cavities in teeth.  If you or your children need fillings, you should discuss the materials available for fillings with your dentist and work with him or her to determine which type is best for you 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 mercury which is sometimes added illegally because it can block melanin production.

Significant Statistics

Mercury is transported long distances, so even remote regions of the world can accumulate mercury pollution from distance sources.

Committee on the Significance of International Transport of Air Pollutants, et al.  Global Sources of Local Pollution An Assessment of Long-Range Transport of Key Air Pollutants to and from the United States.  Washington, D.C.: National Academy Press, 2010.  . http://books.nap.edu/catalog.php?record_id=12743.

Some countries, including Canada and some European countries, recommend that pregnancy women not have dental amalgam fillings placed or removed.  They also issue warnings for young children, nursing women and people with kidney problems who are considering amalgam fillings.

Dental Amalgam Fillings: Environmental and Health Facts for Dental Patients.  Vermont Advisory Committee on Mercury Pollution.

http://www.mercvt.org/PDF/DentalAmalgamFactSheet.pdf.

Coal burning power plants are the biggest source of human-caused mercury in the environment in the United States, with 50% of mercury emissions from this single source.

Mercury: Basic Information.  US EPA.  June 15, 2010.  http://www.epa.gov/mercury/about.htm.

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 and Seafood Charting a Course for the Safety Choices 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 the EPA’s 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) Turn down the temperature.
   
    4) Shut doors to other parts of the house and leave the area.
   
    5) Call your local or state health or environmental agency.
   
    If more than two tablespoons spill, it is mandatory to call the National Response Center at (800) 424-8802.

 
• When possible, recycle old computers and electrical equipment, which often contain mercury in switches..  Visit NextWorth to get rid of some old electronics or media.  Check with your computer’s manufacturer to see if it has a take-back program.

 
• 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. For more detailed information, see the Monterey Bay Aquarium’s Seafood Recommendations. The fish they rate as greenest includes albacore tuna (troll- or pole-caught, from the U.S. or British Columbia), freshwater coho Salmon (farmed in tank systems, from the U.S.), mussels (farmed), oysters (farmed), Pacific Sardines (wild-caught), rainbow trout (farmed), salmon (wild-caught, from Alaska).
   
    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

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/mercury1.htm

Mercury in the Environment. USGS. February 19, 2009. http://www.usgs.gov/themes/factsheet/146-00/.

Frequently Asked Questions: Information on Compact Fluorescent Light Bulbs (CFLs) and Mercury. US EPA. July 2008.

http://www.energystar.gov/ia/partners/promotions/change_light/downloads/Fact_Sheet_Mercury.pdf

Other government agencies

U.S. Environmental Protection Agency

Ariel Rios Building
1200 Pennsylvania Avenue, NW
Washington, DC 20460-0003

http://www.epa.gov/ost/fish/

U.S. Food and Drug Administration

Center for Food Safety and Applied Nutrition
5100 Paint Branch Parkway
College Park, MD 20740
1-888-SAFEFOOD

http://www.fda.gov/Food/default.htm

Agency of Toxic Substances and Disease Registry
4770 Buford Hwy NE
Atlanta, GA 30341
(800) 232-4636
http://www.atsdr.cdc.gov

Nonprofit organizations

Health Care Without Harm

HCWH Membership Services
12355 Sunrise Valley Dr., Suite 680
Reston, VA 20191
703-860-9790

http://www.noharm.org

Environmental Working Group
1718 Connecticut Ave., N.W. Suite 600
Washington, DC 20009
202-667-6982

http://www.ewg.org

SAFE MINDs (Sensible Action for Ending Mercury-Induced Neurological Disorders)
16033 Bolsa Chica St. #104-142
Huntington Beach, CA 92649
404-934-0777

http://www.safeminds.org

Mercury Policy Project
1420 North Street
Montpelier, VT 05602
802-223-9000

http://www.mercurypolicy.org/

Other websites

Got Mercury?

http://www.gotmercury.org

Environmental Defense Chemical Scorecard

http://www.scorecard.org

Institute For Vaccine Safety, Johns Hopkins University

http://www.vaccinesafety.edu

LampRecycle.org

http://www.lamprecycle.org

Institute for Vaccine Safety's Thimerosal Content in Some U.S. Licensed Vaccines

http://www.vaccinesafety.edu/thi-table.htm

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