Mercury Threat To Fetus Raised
EPA Revises Risk Estimates
By Guy Gugliotta
Washington Post Staff Writer
Friday, February 6, 2004; Page A03
A new government analysis nearly doubled the estimate of the number of newborn children at risk for health problems because of unsafe mercury levels in their blood. Environmental Protection Agency scientists said yesterday that new research had shown that 630,000 U.S. newborns had unsafe levels of mercury in their blood in 1999-2000.
The key factor in the revised estimates is research showing differences in mercury levels in the blood of pregnant women and their unborn children. In a Jan. 26 presentation at EPA's National Forum on Contaminants in Fish, in San Diego, EPA biochemist Kathryn R. Mahaffey said researchers in the last few years had shown that mercury levels in a fetus's umbilical cord blood are 70 percent higher than those in the mother's blood.
"We have long known that the effects of methyl mercury on the fetal nervous system are more serious" than on adults, Mahaffey said in a telephone interview yesterday. "But we did not routinely measure [umbilical] cord blood. We had thought that the mother and the fetus had the same level."
Jane Houlihan, a vice president of the Environmental Working Group, noted that the study "for the first time . . . calculated the number based on children's blood levels, not mothers'. The EPA analysis is showing that even if even if the mother is below the danger zone, she can give birth to a baby that's over the limit."
Mercury, a heavy metal, is a highly toxic substance that can seriously damage neurological tissue. Poisoning can lead to learning disabilities, lower intelligence and overall sluggishness. Fetuses, infants and young children are especially vulnerable. Recent advisories from EPA and the Food and Drug Administration have cautioned pregnant women on the dangers of eating tuna and other large predatory fish and shellfish, whose tissues absorb elevated levels of mercury.
EPA has said the largest U.S. sources of mercury contamination are coal-fired power plants, whose annual atmospheric emissions contain 48 tons of mercury. Much of it drifts into the ocean.
The Bush administration is proposing a new regulation requiring power plants to cut mercury emissions 29 percent by 2007 and 70 percent by 2018. Environmental advocates say the industry can achieve significantly deeper reductions.
Mahaffey, a top scientist in EPA's Office of Prevention, Pesticides and Toxic Substances, said she began developing her new estimates of the number of infants at risk by studying research published last year from New Jersey and Maine. The information helped her revise the formula used to extract data from a survey conducted by the Centers for Disease Control and Prevention in 1999-2000 on mercury levels in pregnant women's blood.
The new formula showed that one out of six pregnant women had mercury levels in their blood of at least 3.5 parts per billion, sufficient for levels in the fetus to reach or surpass the EPA's safety threshold of 5.8 parts per billion. In 1999-2000, the last year for which government data are available, this meant that 630,000 children were at risk instead of the original estimate of 320,000.
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