Advisory
2002-41
May 29, 2002
For immediate release
Information on mercury levels in fish
OTTAWA - Mercury continues to be an issue of interest to food regulators and consumers. The purpose of this notice is to:
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advise 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 (Note that this advisory does not apply to canned tuna).
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reiterate advice previously issued by Health Canada based on the potential exposure to mercury that can occur through eating these species over a lifetime (mercury levels in these fish may be higher than the levels found in most commercial fish) and review the issues surrounding the presence of mercury, a naturally-occurring contaminant in fish.
Mercury exposure
Mercury is a naturally-occurring element which is 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 in the inorganic form. The mercury in lakes, streams and oceans can be transformed by bacteria to methyl mercury, an organic and more toxic form. Methyl mercury is the predominant form of mercury in fish and binds tightly to the proteins in fish tissue. Methyl mercury is of greater health significance because it is the form to which humans are primarily exposed when consuming fish as food. Furthermore, since methyl mercury tends to concentrate or "bioaccumulate" in the food chain, predatory fish species tend to have higher levels than non-predatory fish 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 commercial fish. This guideline is enforced by the Canadian Food Inspection Agency (CFIA). It was first set in the 1970s 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 that are known to exceed the 0.5 ppm guideline. Mercury levels for these species generally remain between 0.5 and 1.5 ppm, allowing for occasional consumption. Therefore, these species (Note: not canned tuna) are exempted from the 0.5 ppm guideline and, in their case, another risk management strategy is followed, namely, issuance of advisories recommending appropriate restrictions on (amounts and frequency of) consumption. In this way, these species can continue to be enjoyed by consumers as part of an occasional meal.
Fish are an excellent source of high-quality protein, and are low in saturated fat, which makes them a healthy food choice. Because of nutritional value, 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 child-bearing age and young children are advised to limit their consumption of shark, swordfish and fresh and frozen tuna to no more than one meal per month. For others in the population, a consumption level of no more than one meal per week is recommended for these species.
It is important to note that this limiting advice does not apply to canned tuna. Canned tuna is subject to inspection and enforcement of the 0.5 ppm guideline. The use of smaller, younger tuna in the canning process makes it possible for mercury levels in canned tuna to fall within the 0.5 ppm guideline. Smaller, younger fish have not accumulated higher levels of this contaminant.
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, the CFIA has posted a fact sheet on its website entitled Mercury and Fish Consumption.
For more information, visit the websites for Health Canada and the Canadian Food Inspection Agency at:
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Media Inquiries:
Margot Geduld
Health Canada
(613) 957-1588
Canadian Food Inspection Agency (CFIA)
(613) 228-6682
Public Inquiries (Health Canada):
(613) 957-2991
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