Advisory
2001-60
May 29, 2001
Information on mercury levels in fish
Recent media articles about mercury levels in certain species of fish may have caused some consumers to question the safety of these fish products. Here is some clarification.
Health Canada advises Canadians to limit consumption of shark, swordfish and fresh and frozen tuna, to one meal per week. Pregnant women, women of child-bearing age and young children should eat no more than one meal per month.
This advice is based on the potential exposure to mercury that can occur through eating these gourmet species over the course of a lifetime. Mercury levels in these fish may be higher than the levels found in most commercial fish.
Mercury exposure
Mercury is a naturally-occurring element found in soil and rocks, and also exists in lakes, streams and oceans. In addition to natural sources, mercury is released into the environment by human activities such as pulp and paper processing, mining operations, and burning garbage and fossil fuels.
In the aquatic environment, mercury is usually found as a chemical compound called methyl mercury, which binds tightly to the proteins in fish tissue. Most fish have trace amounts of methyl mercury, and when its level in the aquatic environment is high, its level in fish is high as well. Furthermore, mercury tends to accumulate in the food chain, so predatory fish species tend to have higher levels than non-predatory fish or species at lower levels in the food chain.
Health Canada guidelines
Health Canada has established a guideline level of 0.5 parts per million (ppm) for mercury in most commercial fish. This guideline is enforced by the Canadian Food Inspection Agency (CFIA). It was first set in the 1970's and, based on a recent re-evaluation, is still considered appropriate to ensure that the health of Canadians is protected from the toxic effects of methyl mercury.
Certain fish species sold in Canada, namely, shark, swordfish, and fresh and frozen tuna, contain mercury at levels which are known to exceed the 0.5 ppm guideline. Based on current data available, average mercury levels in these species are at or near 1.0 ppm (the current guideline for methyl mercury in the United States) with a typical range of 0.5 - 1.5 ppm. Application of the 0.5 ppm mercury guideline to these species would virtually eliminate these types of fish from the Canadian diet.
All fish are an excellent source of high-quality protein, are low in saturated fat, which make them a healthy food choice. Because of this nutritional value, gourmet fish continue to be available to Canadian consumers, with advice to limit consumption to avoid exposure to hazardous levels of mercury. Specifically, pregnant women, women of childbearing age and young children are advised to limit the consumption of shark, swordfish and fresh and frozen tuna to no more than 1 meal per month. For others in the population, a consumption level of no more than 1 meal per week is recommended for these species. It is important to note that such advice does not apply to canned tuna. Mercury levels in canned tuna are typically well below the 0.5 ppm guideline.
Health Canada has issued consumer advisories recommending limits to the consumption of shark, swordfish, and fresh and frozen tuna, for example, in the 1999 Health Canada publication entitled Nutrition for a Healthy Pregnancy. This publication was distributed to a variety of audiences, including the Pediatricians of Canada, the Society of Obstetricians and Gynecologists of Canada, the Canadian Medical Association, the Family Physicians of Canada, and the Canadian Nursing Association. It is also posted on the Health Canada website. In addition, CFIA has posted an advisory on its website entitled  Mercury and Fish Consumption.
For more information, visit the websites for Health Canada and the Canadian Food Inspection Agency at:
Media inquiries:
Ryan Baker
Health Canada
(613) 941-8189
Catherine Lappe
Office of Allan Rock
(613) 957-0200
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