Silver dental fillings, officially known as amalgam fillings, contain mercury that may pose a safety concern for pregnant women and young children, warned the U.S. Food and Drug Administration (FDA) as quoted by media reports Friday.

In the past, regulators have warned pregnant women against eating certain fish that contain high levels of mercury, but FDA said mercury in fillings may cause danger to a developing human's brain, in response to a lawsuit filed on behalf of various groups.

FDA posted the precaution on its Web site to settle a lawsuit, making the move a victory for anti-mercury activists.

The warning is not aimed at the general population, only at two groups already urged to limit mercury from another source -- seafood -- because too much can harm a developing brain.

The fillings "contain mercury, which may have neurotoxic effects on the nervous systems of developing children and fetuses," reads the FDA warning.

That doesn't mean it truly harms, and the FDA advised against removing existing fillings. Silver-colored fillings have been used by dentists for over a hundred years to treat cavities in teeth.

The agency still is studying whether the small amount of mercury vapor released by chewing and brushing is enough to cause neurologic disorders or other problems in youngsters.

There have been only a handful of rigorous studies comparing children given either amalgam fillings or tooth-colored resin composite fillings that are mercury-free -- and those studies haven't detected any brain problems.

Nor has that research settled the long-simmering scientific controversy. Two years ago, the FDA's own independent scientific advisers said that while amalgam fillings were safe for most people, more research was needed about potential effects on fetuses and children under six.

(Xinhua News Agency/Agencies June 13,2008)