About Mercury and Canned Tuna


Q: What is Mercury?

Mercury is a naturally occurring metallic substance found in the soil, rocks, lakes, streams and oceans. It can be found in minute quantities in air, water, and all living matter. Mercury is also released into the environment through human activities and pollution.


Q: Why is Mercury Found 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 that binds tightly to the proteins in fish tissue. Most fish have trace amounts of methyl mercury.

The level of mercury in fish is directly related to the amount in its aquatic environment, its place in the food chain and the age of the fish. The older larger fish have more then the smaller younger fish.


Q: Have any Guidelines been set up for consumption of fish containing mercury?

Canada and the United States have set guidelines for total acceptable mercury content in commercial marine and freshwater fish. Health Canada's Guidelines for total mercury content in commercial marine and freshwater fish is .5 parts per million (ppm). This limit is more stringent than the limits set in many other countries. The United States limit for methyl mercury is 1.0 ppm.

Although nearly all fish contain trace amounts of methyl mercury, the levels for most fish range from less than .01 ppm to .5ppm. However, certain types of fish should be eaten in moderation because mercury levels in those fish sometimes exceed the stated mercury level guideline. The fish with the highest mercury levels are larger fish such as sharks, swordfish and very large tuna, typically sold as fresh steaks or sushi (not canned). Due to the higher level of mercury in these species consumers have been advised by the FDA and Health Canada to limit their consumption to one serving a week (Note that this restriction does not apply to canned tuna because of the type, age and size of tuna used in canning.


Q: Why do certain types of fish have higher levels of Mercury than others?

The level of mercury found in fish is related to the level of mercury in its aquatic environment and its place in the food chain. Fish absorb mercury from water as it passes over their gills and as they feed on aquatic organisms. Therefore, larger predator fish are exposed to higher levels of methyl mercury from their prey.


Q: Why does this restriction not apply to canned tuna?

The tuna used in canned products are commonly younger than those used in the fresh and frozen market and have not accumulated high levels of mercury in their bodies.


Q: Does Raincoast Trading test its Tuna for mercury?

Even though canned tuna has been excluded from any restrictions, Raincoast Trading continues to test its tuna to ensure complete consumer safety. Our Tuna remains well below the Canadian and US stated safe levels. Raincoast Trading uses only Albacore tuna for its canned tuna products. As previously stated, the Albacore Tuna used is a much smaller fish and therefore will contain even lower traces of mercury than other light meat canned tuna products.