Author: JENNIFER LEE
Source: The New York Times
February 10, 2004

More than one child in six born in the United States could be at risk for
developmental disorders because of mercury exposure in the mother's womb,
according to revised estimates released last week by Environmental
Protection Agency scientists.

The agency doubled its estimate, equivalent to 630,000 of the 4 million
babies born each year, because recent research has shown that mercury tends
to concentrate in the blood in the umbilical cord of pregnant women.

The Centers for Disease Control and Prevention estimates that one woman in
12 of childbearing age has a mercury level in the blood that poses a
concern. But recent research has shown that the umbilical cord can have an
average mercury concentration 1.7 times as great as the concentration in the
mother's blood.

The senior mercury researcher at the E.P.A., Dr. Kathryn Mahaffey, said a
newborn could exceed the safety concentration level of 5.8 parts per billion
in a mother whose mercury concentration was just 3.5 parts per billion.
Exceeding the safety level does not necessarily mean that a baby will have
impaired development, because researchers build in a cushion between a
defined safety level and the level known to show harm.

Moreover, the mercury level in umbilical cord blood does not necessarily
match the level in the fetus.

Researchers say the estimates, presented last month at the National Forum on
Contaminants in Fish in San Diego, could change as federal scientists
reassess risks. Nonetheless, the new estimates fuel a continuing debate on
the hazards of methylmercury, an organic mercury compound that concentrates
in large marine animals and humans.

The Food and Drug Administration and the E.P.A. issued a more conservative
advisory that cautioned pregnant women and young children to limit fish and
shellfish to two to three meals a week.

Mercury pollution has become a contentious environmental issue with the Bush
administration's proposal to create a market-based trading-pollution system.
Advocates have been pushing for stricter limits on mercury emissions from
power plants, which emit almost 50 tons of mercury annually. But the direct
chemistry of how and whether power plant emissions end up in human beings is
still being cleared up.

"I think between these new calculations and research findings, it is now
abundantly clear for this government to get serious about mercury
polluters," Linda Greer, a scientist with the Natural Resources Defense
Council, said. "We just can't watch these numbers go up in the bloodstream
of American women."