Mercury in tuna: two new reports miss the boat

Ask most people about the benefits of eating fish and they’re likely to opine on the virtues of the omega-3 fatty acids in fish oils that can help curb heart disease and cancer. Ask them about how to avoid risks from mercury in fish and you’re likely to get a range of answers, due in part to conflicting advice about how much tuna and other mercury-bearing species is safe to eat. Two new reports from the Institute of Medicine (IOM) and the Journal of the American Medical Association (JAMA) acknowledge that consumers need better and more comprehensive fish consumption advice, but do little to clear up the confusion.

Both these reports fail to specifically address the unique risks of mercury posed to pregnant women and young children, especially in reference to tuna, relying on the same limited advice that FDA provides. The IOM report gives the same guidance for pregnant women, women of childbearing age and children up to 12 years of age: that it’s okay to have 6 ounces per week of albacore and up to 12 ounces of chunk light. The JAMA study refers only to the FDA and EPA advice, which Consumers Union believes does not go far enough.

"While we agree with the Journal of the American Medical Association and the Institute of Medicine that fish is an important source of protein and contains heart-protecting omega-3 fatty acids, we’re disappointed that neither of these reports takes into account the variations in mercury levels found in the cans of light and white tuna (albacore) sampled by the FDA nor the potential impact on the most vulnerable populations," says Jean Halloran, Director of Food Safety Initiatives for Consumers Union, nonprofit publisher of Consumer Reports. Levels in some of the canned tuna samples tested by FDA (posted on their website http://www.cfsan.fda.gov) contained mercury levels that were very high --in a few cases as high as levels found in some of the fish that these organizations say women of childbearing age should totally avoid, such as king mackerel.

CU is also concerned that both reports downplay risks associated with PCB levels, which can be higher in some species than others. For example, a study published in the Jan. 9, 2004, issue of Science found that farmed salmon had more dioxins and PCBs than wild. The most-contaminated fish came from Europe; farmed salmon from North and South America were somewhat cleaner but still not as clean as wild salmon.

In light of these new studies, Consumers Union is reinforcing its advice that pregnant women take the precautionary measure to avoid canned tuna and that young children minimize exposure. This precaution is further bolstered by another recent study, published online in September in the journal Environmental Health Perspectives, which found that pregnant women who had pre-term births (prior to 35 weeks) were more likely than women delivering at term to have mercury levels (measured in hair) at or above the 90th percentile of the women included in the study.

Consumers Union also offers the following fish consumption advice:

• Pregnant women should avoid all tuna.
• Pregnant women and women of childbearing age should choose fish that are lower in PCBs (i.e. choose wild caught or canned salmon over farm-raised salmon).
• Young children up to 45 pounds should, depending on their weight, only eat about one-half to one 6-ounce can (roughly 4.5 ounces drained) of chunk-light tuna per week, or up to one-third of a can of solid-light or white-tuna.

For more information, read our the full articles on mercury in tuna and  farmed and wild-caught salmon.