How has mercury contamination of fish happened and why is it important?

April 30, 2012 Print Friendly and PDF

Fish is a great source of low-calorie protein for everyone’s diet.  Some fish, though, are contaminated with high levels of methylmercury and other harmful chemicals.  These chemicals can contribute to health hazards in people who may eat large amounts of contaminated fish.

Mercury is a naturally occurring element found in the air, water and soil.  Mercury has also contaminated the environment mainly because of coal burning power plants.  Mercury found in the power plant air pollution may contaminate the air, water and soil when it is spread by the wind and weather.   When mercury contaminates water, like in a lake, it is changed into a more harmful chemical called methylmercury.  Fish that live in water contaminated with methylmercury often become contaminated with mercury making them unsafe to eat.        

The most common way people are exposed to methylmercury is by eating contaminated fish or shellfish.  Scientific studies have shown that by eating large quantities of contaminated fish or eating contaminated fish too often, chemicals in these fish can build up in the human body.  These chemicals can harm the immune system, reproductive system, brain functions and increase risks of certain cancers.  Infants and children that have a lot of exposure to these chemicals may develop physical, mental or behavioral problems that they would not have had otherwise.  This is why children, pregnant women and women who may become pregnant are much more at risk and should limit eating certain species of fish.

Local, state and the federal government agencies publish fish consumption advisories based on scientific data they obtain from monitoring water for contaminated fish.  Some advisories are for specific bodies of water – like a lake or river.  These advisories suggest which types of fish people should avoid or eat in limited quantities.  Many advisories also include information about certain species of fish that are safe for most everyone to eat.    

Almost every state in the U.S. has fish consumption advisories for methylmercury. To find information about fish consumption advisories in your state, you can visit the U.S. Environmental Protection Agency’s Fish Advisory website.  Here you can learn about which species of fish may be unsafe to eat as well as which species of fish are safe to eat.



environmental contamination

environmental health


human health

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