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Mercury in Fish - What You Need to Know

Most fish contain trace amounts of mercury. For most people, the small amounts in fish do not pose a problem. Some fish, however, contain high amounts of mercury, and that is why certain people must be careful about the amounts and type of fish they eat.

  • These people include:
    • women of childbearing age,
    • pregnant women,
    • nursing mothers, and
    • young children

How Does Mercury get into fish?

Mercury is released into the air, water and soil when fossil fuels such as coal are burned. It travels long distances with the wind and is deposited in water. It can also be found in the environment naturally.

Once in water, mercury is transformed by bacteria into methylmercury, its most toxic form. Methylmercury works its way up the food chain, where it can become concentrated in larger, older fish that eat other fish. It is stored in the muscle of fish, so trimming the fat from fish does not reduce mercury.

Mercury Cycle

Download full size Mercury Cycle image (1 page, 3.41MB)

The Health Effects of Mercury

Pregnant women, unborn babies and infants

Both young children and unborn babies are especially susceptible to the effects of mercury. Mercury is toxic to a child’s developing central nervous system.

Mercury can cross the placenta where it builds up in the fetal brain and other parts of the body. It can also pass to an infant through breast milk.

Women of childbearing age

Mercury is a concern before a woman becomes pregnant. It is stored in the body for over a year and can be released during pregnancy. Therefore, higher-mercury fish should be limited or avoided by women of childbearing age.

The benefits still outweigh the risks!

Media reports about the dangerous effects of mercury and other contaminants in fish may make you nervous about eating fish; however, the health benefits of eating fish are greater than the risks. For example, salmon is an excellent source of high-quality protein and is one of the best sources of omega-3 fatty acids. According to Health Canada, salmon is safe and healthy for you and your children.

Contaminants in Fish

Other contaminants such as PCBs, dioxins and flame retardants are also found in fish.

Removing the skin and some of the brown, fatty meat before cooking will reduce the amount of some contaminants, but not mercury.

Trimming fish

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Revised: Friday July 30 2010

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