Mercury and Fish: A Disquieting New Study : Food Safety: Are federal standards for methyl mercury in seafood too low? FDA testing has prompted a call for reducing allowable levels of the toxic metal.

Illegal levels of methyl mercury, a toxic metal that poses special health risks to infants, children and pregnant women, was found in one in five samples of commercially caught swordfish and shark in a three-year review by the U.S. Food and Drug Administration.

The findings prompted a special year-long review by the FDA in 1992; the results are pending.

Methyl mercury, like lead, is found throughout the environment. Once consumed, the heavy metal can accumulate in the tissue of fish, animals and humans. At elevated levels, poisoning can occur. Fetuses exposed to elevated mercury levels can suffer from mental retardation, lack of physical development and seizures. In adults, the symptoms include sensory damage, skin abnormalities and lack of motor skills. Highly elevated levels can cause death.

Seafood is the single largest dietary source of methyl mercury. Because shark and swordfish are at the top of the ocean’s food chain and regularly consume smaller fish that contain mercury, they tend to have higher concentrations of the metal than other fish.

FDA laboratories are currently analyzing 200 samples of imported and domestic shark and 200 samples of imported and domestic swordfish. Each sample is a composite of an entire shipment--or lot--and contains fish of various sizes in order to achieve a representative mix. These results have yet to be released.

However, as much as twenty-six percent of samples tested as recently as 1989 exceeded the allowable level of one part per million of methyl mercury.

“Anytime we see a 15% to 25% violation range, we don’t like it,” says John Jones, FDA’s strategic manager of pesticide and chemical contaminants.

What’s more, if the tests had used the more conservative Canadian standard (Canada allows only 0.5 ppm of mercury in seafood), none of the shark and swordfish sampled by FDA would have passed (all exceeded 0.8 ppm). Public Voice for Food & Health Policy, a Washington-based consumer group, petitioned the FDA more than a year ago to lower the amount of mercury permitted in seafood.

“Basically, FDA has failed in its duty to protect sensitive groups such as pregnant women and children from the adverse effects of methyl mercury,” says Caroline Smith DeWaal, a Public Voice attorney. “They have numbers and data that they can use to set more protective standards and they are failing to act.”

Smith DeWaal says that when the FDA established the current one ppm limit, it considered what may cause mercury poisoning in adult males, not fetuses, infants or children. (Many environmentalists point out that the government’s allowable pesticide levels in food similarly do not take into account infants’ and children’s heightened sensitivity to toxic chemicals.)

Tom Billy, director of FDA’s Office of Seafood, says the agency has reviewed all the scientific literature on methyl mercury and will shortly begin the regulatory process that may pave the way for reductions in the allowable levels of the toxin in food.

“We take this issue seriously and we are addressing it,” he says.

Yet an authoritative study by the National Academy of Sciences in 1991 concluded that the FDA “lags badly in the development of innovative methodology for assessing risks (from compounds such as methyl mercury).” The academy also noted that the FDA was “most conspicuously backward” in determining the threat from non-carcinogenic compounds such as mercury.

Billy says that since the National Academy of Sciences report was released, the FDA has worked with the Environmental Protection Agency to improve its risk assessment capabilities. One such effort is a major study of methyl mercury’s effects on mothers and young children with high seafood consumption rates. The study, expected to be concluded later this year, is being conducted on the Seychelles Islands in the Indian Ocean.

Despite the concerns about methyl mercury in fish, the FDA says the detectable levels have remained the same throughout this century and are not on the rise. Billy says that in the early ‘70s, when methyl mercury was recognized as a serious contaminant in canned tuna, the Smithsonian Institution provided data indicating that mercury levels in tuna were the same as in the 1800s.

Although canned tuna has only one-tenth the levels being found in fresh swordfish and shark, the greatest source of methyl mercury in the diet may still be from canned tuna. Even so, FDA officials say that recent measures enacted by the seafood industry have resulted in reduction of mercury levels in tuna. The practice of dolphin-friendly tuna fishing has inadvertently resulted in a shift in the target catch from species with high mercury levels to those with lower concentrations.

Billy adds that regular laboratory testing by domestic processors and seafood importers can also play a role in reducing the number of fish with elevated methyl mercury levels that enter the commercial food chain.

Not every group feels that increased testing is necessary. The National Fisheries Institute, a seafood industry trade group, takes the position that all the available scientific literature indicates mercury levels in fish do not pose a hazard. “People who are at risk for mercury should limit or restrict their consumption of certain fish--such as swordfish and shark--to once a month,” says Clare Vanderbeek, vice president of the trade group. “In any event, it would be unique for someone to eat shark or swordfish much more than that since present consumption rates indicate the typical consumer is eating seafood about twice a month.”

Vanderbeek also says that the Fisheries Institute opposes any reduction in the federal government’s allowable levels of mercury in seafood.

“In 20 years of attention to this issue, there is no indication of a health problem,” she says. “There is no evidence that warrants lowering the one ppm level (of mercury allowed in seafood). And if there were such evidence then we would be the first ones to request a reduction.”