Mercury Impacts
Mercury is a metal that is a liquid at room temperature. Mercury is known as a “heavy metal” because it is very dense. One cup weighs more than 6.5 pounds. Mercury can be toxic to humans, fish, and wildlife.
Harmful effects of mercury
Emissions from coal-fired power plants are the single largest human-caused source of mercury in the environment. Coal plants contribute approximately one-third of all human-caused mercury. Coal-burning power plants are the only major source of mercury pollution in the United States that is not regulated by the government. When coal is burned at a power plant, mercury is released from the smoke stack and is ultimately deposited on land and in our rivers, streams, and lakes.
Most human exposure to mercury comes from eating contaminated fish. Mercury accumulates in fish in a severely toxic form known as methylmercury. Over 40 states have mercury advisories warning consumers not to eat fish caught in certain lakes, streams, and other water bodies. We’ve created a 
mercury cycle graphic (pdf 2.1 mb) that shows how mercury gets into the environment and how fish are affected.
The U.S. Environmental Protection Agency (EPA) estimates that as many as seven million adults and children are regularly eating mercury-contaminated fish at unsafe levels. Mercury exposure at toxic levels can cause damage to vision, coordination, nervous system and brain function in adults and children. In addition, fetuses are particularly vulnerable to mercury poisoning, which can inhibit development and cause severe birth defects. Women are advised against eating fish with elevated levels of mercury both before and during pregnancy.
The last decade has shown a steady, nationwide increase in the percentage of water bodies under fish consumption advisories for mercury. See the table below. New coal-fired power plants that do not incorporate rigorous mercury reduction technologies will make the problem worse.
The EPA is under a legal requirement to regulate mercury emissions at coal-fired power plants by January of 2008. The EPA determined in 2001 that existing technologies are able to remove as much as 90 percent of mercury from coal plant smokestacks This would reduce mercury emissions from the current level of nearly 50 tons per year to only 5 tons per year. However, the EPA’s proposed regulations, set to take effect in December 2004, would allow six to seven times more mercury pollution into the air for a decade longer than its 2001 determination.
Massachusetts recently passed a law requiring 85% removal of mercury from coal plant emissions by 2008.
For further information, please read the following reports:
- Clear The Air’s recent report entitled Toxic Neighbors discusses toxics released by coal-fired power plants.
- Pollution Probe’s Mercury in the Environment: A Primer is a comprehensive introductory report about mercury.
- Environmental Working Group’s Mercury Falling assesses mercury pollution from coal-fired power plants.