Chemical Contamination - Mercury


Mercury In Our Food 

In the Chesapeake watershed, mercury is responsible for more waters listed with fish consumption advisories than any other pollutant. Practical, cost-effective solutions can protect both public health and the natural resources of the Chesapeake Bay.

Mercury in the Environment

Mercury is a highly toxic chemical, especially to the developing nervous system, and can cause IQ deficits in children. For this reason, fetuses, infants, children, and women of childbearing age are at greatest risk.

Mercury increases in concentration as it moves up the food chain as wildlife, fish, and people consume contaminated food. For example, the amount of mercury in fish tissue can be more than a million times higher than in surrounding water.

Though mercury is a naturally occurring element, two-thirds of the mercury moving through the environment is a product of human activities. In many cases, contaminated waters are in areas considered "pristine" with very little human activity or industry.

Where Is the Mercury Coming From?

One answer is: the air. According to EPA, coal-fired power plants are the largest source of mercury air emissions in the U.S., accounting for more than 40 percent of the pollution. Mercury is found in coal. And when coal is burned to make electricity, mercury flows out of the smokestacks of power plants and other coal-burning sources and is washed by rain into the Chesapeake Bay and other waterways.

The Good News

In December 2011, EPA Administrator Lisa Jackson unveiled the nation's first air pollution standards for mercury and other chemicals emitted from power plants. The regulations were mandated by Congress in 1990, but—until now—have faced roadblocks from litigation and lobbying.

The Mercury and Air Toxic Standards will require power plants to cut mercury emissions by at least 90 percent. CBF and others sued EPA to get these rules in place. This is good news for us, the fish we eat, and the air we breathe. EPA predicts 11,000 fewer premature deaths per year and the potential for 46,000 short-term construction jobs and 8,000 new permanent jobs in the utility industry associated with the installation and maintenance of pollution controls.

Although nearly all fish and shellfish contain trace amounts of mercury, they also contain high-quality protein and omega-3 fatty acids. So, make fish part of your healthy diet, but be conscious of your risk factors, avoid fish with higher mercury levels (like swordfish and shark), and check local advisories on fish you catch in local waters.


The coal industry and its allies continue to try to derail these regulations, claiming that EPA cannot even decide whether to address major hazards to public health and the environment without first considering the effect on the industry's bottom line.

Last year, the D.C. Circuit Court rejected this argument. The coal industry and its allies appealed to the U.S. Supreme Court, which agreed November 25, 2014 to hear the case. On March 25, 2015, the Court heard arguments. Earthjustice, on behalf of Sierra Club, Clean Air Council, Chesapeake Bay Foundation, and the NAACP, is helping EPA defend the rule. Statements from these organizations are available on the Earthjustice website at A decision is expected this summer. More about the case can be found at


Mercury in fish harvested from the Chesapeake Bay and its tributaries is a real concern. An accumulation of toxic mercury in humans can cause damage to the brain, kidney, and lungs.

This infographic shows how mercury travels from power plants to the air and into waterways, only to contaminate plankton and fish which are then consumed by people.

  • Air pollution, primarily from power plants, is the main source of the mercury that contaminates fish in the Bay watershed.
  • Mercury travels through the atmosphere and returns to the earth through precipitation.
  • Mercury makes its way into our waterways when precipitation brings air pollution to the earth.
  • Once mercury is in the water, biological processes can trun it into a highly toxic form called methylmercury.
  • Plankton absorb methylmercury from the water and sediment.
  • Fish eat contaminated plankton and smaller fish, and the methylmercury accululates in their tissues.
  • Humans accumulate mercury in their bodies by eating contaminated fish.

Share Your Clean Water Story

What does the Bay, its rivers and streams mean to you? What impact have the Bay and its local waters had on your life? We'd like to know.

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Do you enjoy working with others to help clean the Chesapeake Bay? Do you have a few hours to spare? Whether growing oysters, planting trees, or helping in our offices, there are plenty of ways you can contribute.

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