Pregnant women should not eat shark, swordfish, king mackerel or tilefish because they may contain enough mercury to damage the fetus's nervous system, the US Food and Drug Administration said on Friday.

Young children, nursing mothers and women who may become pregnant should avoid those fish as well, FDA said in a consumer advisory.

A National Academy of Sciences report issued last July estimated up to 60,000 children a year were born each year who had been exposed to during pregnancy to levels of mercury that could interfer with development of the brain and nervous system.

Even so, seafood, a naturally low-fat source of protein, can be an important part of a balanced diet for pregnant women and women who may become pregnant, FDA said.

"You can safely eat 12 ounces per week of cooked fish," the FDA advisory said. "You can choose shellfish, canned fish, smaller ocean fish or farm-raised fish -- just pick a variety of different species."

Consumer groups wanted fresh tuna, used in sushi or served as tuna steak, added to the warning list as well. "We shouldn't be ignoring the risk there," said Michael Bender of the Mercury Policy Project.

"The question is why fresh tuna steak were not included on the list because they can also pose a risk," said Caroline Smith DeWaal of Center for Science in the Public Interest.

Mercury enters the environment naturally and through industrial pollution. Nearly all fish contain trace amounts of methyl mercury but longer-lived, larger fish that feed on other fish, like shark or swordfish, accumulate the highest amounts of methyl mercury and pose the largest threat to people who eat them regularly.

In a related announcement, the Environmental Protection Agency said pregnant women, women who might become pregnant, nursing mothers and young children should eat only one meal per week of freshwater fish caught by family members or friends.

The agency said a meal for adults should be six ounces of cooked fish and for children, two ounces.

EPA said consumers should check with their state or local health departments for specific advice about local waters.

Six states + Connecticut, Maine, Michigan, Minnesota, New Jersey and Vermont + have issued warnings on methyl mercury in fish. Minnesota, for example, advises pregnant or nursing women against eating swordfish or shark while saying up to seven ounces per week of canned tuna is safe if no other fish containing mercury is eaten.

(From ChinaDaily)