Mercury danger in fish, warns study

Posted: 7 November 2002

A study involving 116 fish-eating men and women in a San Francisco medical practice, showed that nearly 90 per cent had blood levels of mercury surpassing safe levels as set by the US Environment Protection Agency (EPA).

The group were chosen because of their level of fish consumption and because they showed symptoms consistent with mercury poisoning, including depression, memory loss, confusion, tremors, metallic tastes, and hair loss. Mercury is a potent toxin to the brain and nervous system, with foetuses and children at greatest risk.

"Patients in my practice regularly get mercury poisoning from eating commercial seafood," says Dr. Jane Hightower, the internal medicine physician who authored the study. The patients tested included surgeons and CEOs, psychiatrists and wine-makers, geophysicists and internet executives, and their children.

Although her study didn't aim to correlate symptoms with mercury levels, when patients stopped consuming those fish their symptoms got better. The study appeared on November 1, 2002, in the online version of the National Institutes of Health.journal, Environmental Health Perspectives.

"When it comes to buying seafood," adds Hightower, "the motto should be: 'Buyer beware'."

The majority of patients tested had levels at least twice the EPA safe level, while 16 per cent exceeded it by 400 per cent or more. The average blood mercury level for women tested was three times the EPA safe level and ten times higher than the average for the US population, according to a recent survey by the Centers for Disease Control and Prevention (CDC).

The study is likely to add fuel to the years-old controversy over whether the federal Food and Drug Administration (FDA) regulates seafood mercury levels closely enough to protect public health-and especially populations most at risk like children and women of childbearing age.

"It's bad enough our favorite fish species are often too polluted to eat," says David Wallinga, MD, physician and Co-director of the Food and Health Program at the Institute for Agriculture and Trade Policy. "But instead of tracking the problem, FDA turns its back."

The National Academy of Science estimates that every year approximately 60,000 babies are born facing significant risks of disrupted development of the brain and nervous system, due to mothers with high fish consumption and mercury levels. New Center for Disease Control (CDC) findings also indicate that 8 per cent of American women have blood-mercury levels above what EPA considers safe for the developing fetus.

Based on new recommendations from its Food Safety Committee, the FDA is expected to soon come out with a new consumer advisory. The Committee recommended that FDA resume fish testing, add other high mercury seafood to its "do not consume" list and warn pregnant women and young children to limit their consumption of canned tuna, the most consumed fish in America.

In that regard, FDA already lags behind around ten US states that warn regnant women and - in some cases - young children to limit consumption to one or two cans of tuna per week

Fish accumulate methyl mercury from the environment in muscle tissue. No food preparation or practical cooking method can remove it. Major sources of environmental mercury include coal-fired power plants, and the incineration or improper disposal of mercury-containing products, such as thermometers and switches.