Mercury Awareness

What is mercury?

• Mercury is a naturally occurring metal. The metallic mercury is a shiny, silver-white, odorless liquid. Metallic mercury is used to produce chlorine gas and caustic soda, and is also used in thermometers, dental fillings, and batteries.

• Mercury combines with other elements, such as chlorine, sulfur, or oxygen, to form inorganic mercury compounds. Mercury salts are sometimes used in skin lightening creams and as antiseptic creams and ointments.

• Mercury also combines with carbon to make organic mercury compounds. The most common and most toxic one is methylmercury, produced mainly by microscopic organisms in the water and soil.

Why are we concerned about mercury?

Mercury is a toxic persistent, bioaccumulative pollutant that affects the nervous system. Methylmercury is a chemical species that bioaccumulates in fish. Fish consumption advisories are in effect for mercury in thousands of lakes and rivers,  including much of the Great Lakes ecosystem.

How does mercury enter the environment?

Inorganic mercury enters the air from mining ore deposits, burning coal and waste, and from manufacturing plants. It enters the water or soil from natural deposits, disposal of wastes, and volcanic activity.

Methylmercury may be formed in water and soil by small organisms called bacteria. Methylmercury builds up in the tissues of fish.  Larger and older fish tend to have the highest levels of mercury.

How do people get exposed to mercury?

Eating fish or shellfish contaminated with methylmercury. Breathing vapors in air from spills, incinerators, and industries that burn mercury-containing fuels. Release of mercury from dental work and medical treatments. Breathing contaminated workplace air or skin contact during use in the workplace (dental, health services, chemical, and other industries that use mercury). Practicing rituals that include mercury.

How does mercury affect children?

Brain damage, mental retardation, incoordination, blindness, seizures, and inability to speak. Children poisoned by mercury may develop problems of their nervous and digestive systems, and kidney damage.

Sources of mercury in Wisconsin:

Wisconsin DNR has estimated that 50% of the deposition in the state is from in-state sources. 

Source: Wisconsin DNR, Decision on the Need for An Environmental Impact Assessment, Draft, 2001

According to a report from National Wildlife Federation the mercury content in the rain along the Illinois/Wisconsin border is as high as 56 times safe levels.

What are the current mercury regulations? 

• The EPA has set a limit of 2 parts of mercury per billion parts of drinking water (2 ppb).

• The Food and Drug Administration (FDA) has set a maximum permissible level of 1 part of methylmercury in a million parts of seafood (1 ppm).

• The Occupational Safety and Health Administration (OSHA) has set limits of 0.1 milligram of organic mercury per cubic meter of workplace air (0.1 mg/m3) and 0.05 mg/m3 of metallic mercury vapor for 8-hour shifts and 40-hour work weeks.

• The EPA has set standards for mercury in the Great Lakes and all the waters in the Great Lakes basin, including Lake Michigan. These standards were developed during the Great Lakes Water Quality Initiative ("GLI") process and promulgated in regulations. Each Great Lakes state now is required to implement those regulations. The GLI establishes two standards for mercury: one to protect people, and one to protect wildlife. The wildlife standard requires that lakes and streams contain no more than 1.3 parts per trillion (ppt or ng/L) mercury in their water. The human health standard sets a limit of 1.8 ppt mercury in water.

• Wisconsin has adopted the GLI wildlife standard for mercury, and has promulgated an even lower standard for human health: 1.5 ppt. The Wisconsin standards apply to every lake and stream in the state and to Lakes Michigan and Superior.

Relevant website:

• Center for Disease Control (CDC)’s Agency for Toxic Substances and Disease Registry (ATSDR) Profile Information Sheet http://www.atsdr.cdc.gov/tfacts46.html

• Mercury in the environment created by USGS http://www.usgs.gov/themes/factsheet/146-00/