Mercury

Mercury is a shiny, silver-white liquid metal found in natural deposits. If heated, it becomes a colorless, odorless gas. It has been found in toxic sewage sludge, coal emissions and coal waste. The U.S. EPA does not allow mercury in drinking water above the concentration of 2 parts per billion. In sewage sludge applied to land, the U.S. EPA limits mercury to a concentration of 57 parts per million. In the Targeted National Sewage Sludge Survey, a 2009 test of 84 samples of sewage sludge from around the U.S., the EPA found mercury in every sample in concentrations ranging from 0.17 to 8.3 parts per million.

Forms of Mercury
Mercury can be found in a number of different types of compounds. In its inorganic forms, it combines with other elements, such as chlorine, sulfur, or oxygen, to form compounds known as "salts." These salts are usually white powders or crystals. Organic mercury compounds are formed when mercury combines with carbon. One of the most common organic mercury compounds is methylmercury, which is produced mainly by microscopic organisms in the water and soil. Methylmercury is a neurotoxin

Uses
Dry-cell batteries, fluorescent light bulbs, switches, and other control equipment accounts for a large percent of mercury usage. However, metallic mercury is also used in thermometers, dental fillings, and batteries and in some plants that produce chlorine gas and caustic soda. Bills introduced into both the House and the Senate in the 111th Congress would ban the use of mercury in chlorine and caustic soda production, but to date, none of the bills have passed. Mercury salts are sometimes used in skin lightening creams and in antiseptic creams and ointments.

Toxicity
The Centers for Disease Control says the following about mercury's toxicity:

"The nervous system is very sensitive to all forms of mercury. Methylmercury and metallic mercury vapors are more harmful than other forms, because more mercury in these forms reaches the brain. Exposure to high levels of metallic, inorganic, or organic mercury can permanently damage the brain, kidneys, and developing fetus. Effects on brain functioning may result in irritability, shyness, tremors, changes in vision or hearing, and memory problems.

"Short-term exposure to high levels of metallic mercury vapors may cause effects including lung damage, nausea, vomiting, diarrhea, increases in blood pressure or heart rate, skin rashes, and eye irritation."

Mercury and coal
Coal-fired power plants are the largest source of mercury in the United States, accounting for about 41 percent (48 tons in 1999) of industrial releases. According to the Centers for Disease Control and Prevention, eight percent of American women of childbearing age had unsafe levels of mercury in their blood, putting approximately 322,000 newborns at risk of neurological deficits. Mercury exposure also can lead to increase cardiovascular risk in adults. When mercury is deposited on land or in water, microorganisms convert part of it to a highly toxic form called methylmercury. When fish and animals eat these microorganisms, the toxins accumulate and can interfere with reproduction, growth, and behavior, and can even cause death.

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 * Sewage sludge
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 * Mercury and coal