Mercury is a naturally occurring metal that has elemental (metallic), inorganic, and organic forms. Elemental mercury is released into the air from combustion of fossil fuels (primarily coal). Coal-burning power plants are the largest human-caused source of mercury emissions to the air in the U.S., accounting for over 50 percent of all domestic human-caused mercury emissions. Small amounts of mercury compounds are manufactured in the U.S. for specialty uses such as chemical and pharmaceutical applications. Larger quantities of these compounds are generated as byproducts from pollution control activities at gold mines or in waste. Elemental mercury is processed in the U.S. from byproduct mercury compounds, and an unknown quantity of mercury compounds is imported into the U.S. for conversion to elemental mercury.
Burning solid and hazardous wastes (which produces chlorine), as well as the improper treatment and disposal of wastes containing mercury, can also release it into the environment. Mercury in the air eventually settles into water or onto land where it can be washed into water. Once deposited, microorganisms change elemental mercury into methylmercury. The most common way we are exposed to mercury is by eating fish or shellfish that are contaminated with mercury.
People may be exposed to metallic mercury when glass thermometers or other products containing mercury, such as fluorescent bulbs, are broken or when mercury is brought into the home from schools, abandoned industrial sites, or other sites where it may be stored. Metallic mercury evaporates into the air at room temperature and the vapors will accumulate indoors. Breathing mercury vapors in the air is the source of entry of metallic mercury into the human body, therefore, it is important to promptly and properly clean up and dispose of mercury.
Chemicals of Concern:Mercury is a naturally occurring metal which has several forms. The toxic forms of mercury depend on its chemical form and the route of exposure. Methylmercury and metallic mercury vapors are more harmful than other forms.
Elemental or metallic mercury, the form found in thermometers, thermostats, dental fillings, switches, fluorescent light bulbs, and batteries is less toxic than methylmercury, and not easily absorbed into unbroken skin. However, it vaporizes even at room temperature. The higher the temperature, the more vapors are released. If elemental mercury is ingested, it is absorbed relatively slowly and may pass through the digestive system without causing damage. Elemental mercury is used to produce chlorine gas and caustic soda. It may be found in higher concentrations in environments such as gold mine sites, where it has been used to extract gold.
Inorganic mercury compounds or "salts" are formed when mercury is combined with other elements, such as chlorine, sulfur, or oxygen. Ingestion of some inorganic mercury compounds such as the salt HgCl2, which damages the gastrointestinal tract and causes kidney failure, is unlikely from environmental sources. Mercury salts are sometimes used in skin lightening creams and as antiseptic creams and ointments.
Methylmercury is the most toxic form of mercury. Exposure is usually by ingestion; it is absorbed more readily and excreted more slowly that other forms of mercury. It is an organic mercury compound produced mainly by microscopic organisms in the water and soil. More mercury in the environment can increase the amounts of methylmercury that these small organisms make. Methylmercury is biomagnified in the food chain, therefore, larger predatory species like tuna, swordfish, and shark in ocean waters and trout, pike, walleye, and bass in fresh waters contain more methylmercury in their tissues than smaller, non-predatory fish. Also, the older the fish, the more time methylmercury has to accumulate.
Dimethylmercury is rarely used and highly toxic. It is estimated that there are about 20 research groups in the world using dimethyl mercury. Its toxicity was experienced in 1997 by an expert in the mechanisms of metal toxicology, Professor Karen E. Wetterhahn. Professor Wetterhahn died as a result of a tragic laboratory accident, ten months after spilling one to a few drops of dimethylmercury onto her latex glove near her thumb. The dimethylmercury penetrated the glove instantly and penetrated her skin and was absorbed into the blood stream. It took five months until her gait began to falter and her words began to slur. Tests showed that her body contained more than 80 times the lethal dose of mercury.
Implementing Solutions:Please submit your experiences (successes/challenges) and tribal-specific documents to share on our website using the attached form.
Resources:ATSDR Fact Sheet Mercury [pdf]
ATSDR Fact Sheet Metallic Mercury [pdf]
ATSDR Public Health Statement [pdf]
ATSDR Toxicological Profile for Mercury [pdf]
Minnesota Pollution Control Agency Fact Sheet: Cleaning up mercury spills in your school [pdf]
Ohio Environmental Protection Agency Fact Sheet: Mercury in Your Home [pdf]
State of Oregon Department of Environmental Quality Fact Sheet: Common Products Containing Mercury [msWord]
Websites:Mercury in Schools:
Agency for Toxic Substances & Disease Registry: Mercury and Your Health:
Corrosion Doctor's Mercury Resources:
EPA: What's mercury and why is it a concern?
EPA's Roadmap to Mercury:
EPA's Fish Consumption Advisories:
National Tribal Air Association: Mercury:
Emergency Planning, Management, and Response
Hazardous Waste and Emergency Response Training Requirements
Research Individual Chemicals
For more information, please contact:
Todd Barnell, Program Manager
Jennifer Williams, Alaska Program Coordinator, Sr.
Last updated: July 10, 2015