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Study finds increased mercury in big fish eaters
UNITED STATES
Wednesday, October 23, 2002, 00:00 (GMT + 9)
A San Francisco internist’s study of hundreds of Californians who ate more fish in their diets than the federal health and environment agencies recommend has found that nearly 90 per cent ended up with elevated mercury levels in their bodies.
The research, presented by Dr Jane Hightower at a symposium of environmental health experts, is touted as one of the first studies to document mercury levels in Americans who eat more fish than federal agencies suggest. According to a news agency report, Hightower screened 720 patients between March 2000 and March last year, then tested the mercury levels of patients who reported having eaten more than the recommended number of servings of fish a week.
The Food and Drug Administration's present suggestion is that pregnant women and young children limit their fish intake to two six-ounce cans of tuna per week if it's the only fish they eat, and to only one can per week if they also eat other fish. The agency says they shouldn’t eat swordfish, shark, king mackerel or tilefish at all.
About 78 per cent of patients with high mercury levels reported eating canned tuna more than three times a month, while 74 per cent also said they ate salmon more than four times a month. And 72 per cent said they had swordfish more than once a month. Other fish commonly eaten by the patients included halibut, ahi, sea bass and sushi.
The tests showed that of 116 patients who had their blood tested as high fish eaters, 89 per cent showed mercury levels greater than the five parts per million recognised as safe by the National Academy of Sciences.
Of that group, 63 people had blood mercury levels more than twice the recommended level, and 19 showed blood mercury levels four times the level considered safe. Four people had mercury levels as high as 10 times the government’s recommended amount.
The study keys in on a specific group of fish because while there are acknowledged benefits from eating fish as a high quality source of protein packed with heart-protecting Omega 3 fatty acids, some fish are known to have higher levels of mercury than others. Conference attendees are reported not to have been too concerned about the study findings – most of those at the symposium held by the American Fisheries Society and the Environmental Protection Agency are stated to have ordered salmon for their dinner Saturday. Salmon is considered among the safest types of fish to eat.
"We are not talking about whether or not to eat fish," said an EPA official who helped to organise the conference is reported as saying.
The peer-reviewed study, which is slated for publication 1 November in the journal Environmental Health Perspectives, was also reported as having monitored 67 patients as they reduced their fish intake and subsequently their bodies' mercury levels. Within 41 weeks, Hightower told the health experts, all except two had reduced their blood mercury levels to below government-recommended thresholds.
The study was stated as not having addressed physical symptoms such as fatigue or memory loss associated with mercury poisoning. Some patients were said to have reported such problems, but Hightower's study did not attempt to correlate symptoms with mercury levels.
Too much mercury can damage the nervous system, especially in children and fetuses, but scientists are not certain how much mercury-tainted fish is needed to trigger health problems.
By Quentin Dodd
FIS North America
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