Mercury and Fish Consumption

Eating fish offers many nutritional benefits, including protein and omega-3 polyunsaturated fatty acids. However, caution must be taken to avoid eating too much fish containing excessive levels of methyl mercury or other persistent toxic substances. The primary human exposure to methyl mercury is through fish consumption.

In the United States in March 2004, the U.S. Environmental Protection Agency and the U.S. Food and Drug Administration issued a joint consumer advisory on methyl mercury in fish and shellfish for reducing the exposure to mercury in women who may become pregnant, pregnant women, nursing mothers, and young children. The advisory unified and superseded the agencies' 2001 advisories. It advised avoiding fish with relatively high levels of mercury (shark, swordfish, king mackerel, and tilefish), eating up to 12 ounces a week of a variety of fish and shellfish that are lower in mercury (including shrimp, canned light tuna, salmon, pollock, and catfish), and checking local advisories about the safety of fish caught by family and friends in local lakes, rivers and coastal areas (and eating up to 6 ounces a week of fish caught from local waters if no advice is available provided no other fish is consumed that week.)¹⁷

This third, and perhaps most complicated, provision of the EPA’s and FDA’s joint advice has particular resonance in the Great Lakes. Site-specific advisories continue to limit or ban consumption of certain fish caught in the Great Lakes because of methyl mercury contamination. In fact, due to localized contaminated sediment, methyl-mercury related fish consumption advisories are expected to exist for decades to come in some Great Lakes Areas of Concern. As an example, the Guide to Eating Ontario Sport Fish contains detailed advice on selecting fish for eating from Ontario rivers and lakes, including the Great Lakes; recommends not eating any organs, fat or skin of any fish; and advises eating smaller fish, eating bass, pike, walleye, perch, and pan fish from the Great Lakes instead of fatty species such as salmon and trout; and allowing fat to drip away when cooking fish.¹⁸

The Commission previously recommended in its 2000 biennial report that the governments improve fish consumption advisories in the Great Lakes, and the Commission’s Health Professionals Task Force (HPTF) recently reported in detail on this issue. The HPTF members support a more effective approach to the development of fish consumption advisories, through better protection of those people at risk, without deterring the majority of people from fish consumption. To develop such an approach, environmental monitoring and exposure assessments are urgently needed to track trends in persistent organic pollutants. Efforts are needed to continue to reduce contaminant levels in all Great Lakes fish. ¹⁹

The Commission's concerns remain relevant today. Advisories are often technical, sometimes offer conflicting advice, and typically fail to reach at-risk populations, including children and women of child-bearing age.²⁰ For example, according to a study by Kearney and Cole,²¹ only 85% of licensed Ontario anglers were aware of the Guide to Eating Ontario Sport Fish, only 29% had a copy of the Guide and followed its advice at least sometimes, and 27% had a copy of the Guide but never followed the advice. Only 50 percent of Great Lakes sport fish consumers reported awareness of a health advisory. ²² Ontario's development of outreach programs directed at school children in non-english speaking communities (in two Areas of Concern) is an example of a communication tool that could improve these statistics.