News Coverage
Study: Pregnant women eating too much fish
Fetuses may have harmful mercury levels
Published April 7, 2004
Of the 4 million babies born in the USA in 2000, more than 300,000 of them -- and as many as 600,000 -- may have been exposed to ''unacceptable'' levels of methyl mercury because their mothers ate a diet rich in fish, a study finds.
The new study, by researchers at the Office of Prevention, Pesticides and Toxic Substances at the Environmental Protection Agency, repeats a warning by numerous studies that the neurotoxin is particularly dangerous for growing fetuses.
Exposure to even low levels of mercury in utero can cause developmental problems and difficulties with visual and motor integration.
By looking at diet logs and testing blood levels in 1,709 women, researchers found that women who ate fish and/or shellfish at least twice a week had blood mercury concentrations seven times higher than women who didn't eat fish in the previous month. The women were taking part in the National Health and Nutrition Examination Survey in 1999 and 2000.
Using the survey results, the researchers came up with mercury ranges for women in the U.S. population as a whole and extrapolated the number of babies who potentially would be exposed to high levels.
Mexican-Americans participating in the survey had the lowest levels of mercury while those who checked the ''other'' racial category, which includes Asians, Native Americans and Pacific Islanders, had the highest.
The study is published in the April issue of the journal Environmental Health Perspectives.
It emphasizes ''the importance of paying attention to the advisories (on fish consumption for women of child-bearing age) EPA and FDA have worked so hard to create,'' says lead study author Kathryn Mahaffey of the EPA.
The EPA and the Food and Drug Administration revised their guidelines this year on mercury consumption. They advise that children and women of child-bearing age stay away from fish with high levels of mercury: shark, swordfish, king mackerel or tilefish.
The agencies also recommended restricting the consumption of other fish to 12 ounces a week. And no more than 6 of those ounces should be canned albacore tuna, which is higher in mercury than canned light tuna.
The wide variation in the number of babies potentially affected is because of new data that suggest that the level of mercury in a fetus' blood is potentially 70% higher than in the mother's. This may be because the fetus' blood concentrates mercury when it chemically tags along with other important molecules the fetus needs to grow.
Mahaffey cautions that the research is based on only two years of data. ''We predict this will change, but we don't know which way,'' she says.