Food Safety Facts on Mercury and Fish Consumption

• Information Update - Testing for Mercury in Canned Tuna
• Mercury in Fish - Consumption Advice: Making Informed Choices about Fish
• Update - Health Canada advises specific groups to limit their consumption of canned albacore tuna

Fish are an excellent source of high-quality protein and are low in saturated fat which makes them a healthy food choice. However, certain types of fish should be eaten in moderation because mercury levels in those fish sometimes exceed Canada's mercury guideline. Visit the Health Canada website for more information on fish consumption.

What is mercury?

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.

We absorb small amounts of mercury from a number of sources, both natural and artificial, in our immediate environment. These include amalgam dental fillings, air and water pollution, and trace amounts in food. Of the different kinds of food we eat, fish is usually the largest source of mercury.

It is well known that high amounts of mercury can damage the nervous system of people and animals. In trace amounts, however, the effects are not clearly known. Long-term studies are being conducted to determine the effects of low levels of mercury, especially on young children.

Mercury in fish

Mercury exists in two different forms, the organic and the inorganic. In the aquatic environment, the most prevalent form of mercury is methyl mercury, the organic form, which binds tightly to the proteins in fish tissue. Most fish have trace amounts of methyl mercury. The level of mercury found in a fish is related to the level of mercury in its aquatic environment and its place in the food chain. Mercury tends to accumulate in the food chain, so large predatory fish species tend to have higher levels than non-predatory fish or species at lower levels in the food chain.

The CFIA's role

The CFIA regularly tests commercial fish and shellfish to determine if it meets the Canadian mercury guidelines and to establish baseline levels for particular species in particular aquatic environments. Fish and fish products for sale in Canada must meet the mercury guidelines set by Health Canada.

Freshwater fish

Levels of mercury in freshwater fish vary according to the lake or river system from which they are harvested, and as with marine fish, predatory species tend to have higher levels than non-predators. All commercial, freshwater fishing areas are surveyed and where high levels are found, they are closed to commercial fishing or restrictions are placed on catching and marketing certain species.

With regards to recreational fishing, it is normally the responsibility of provincial governments to monitor mercury levels and to set and publicize safe consumption standards and guidelines. For more information regarding the safety of recreationally-caught freshwater fish for consumption, contact provincial authorities.

P0083E-02
March 2007