For the first time, the FDA has issued a warning that the mercury contained in silver dental fillings may pose neurological risks to children and pregnant women.

"Dental amalgams contain mercury, which may have neurotoxic effects on the nervous systems of developing children and fetuses," reads a statement that has been added to the agency's Web site. "Pregnant women and persons who may have a health condition that makes them more sensitive to mercury exposure, including individuals with existing high levels of mercury bioburden, should not avoid seeking dental care, but should discuss options with their health practitioner."

The warning was one of the conditions that the FDA agreed to in settling a lawsuit filed by several consumer health groups.

"Gone, gone, gone are all of FDA's claims that no science exists that amalgam is unsafe," said Charles Brown, a lawyer for Consumers for Dental Choice, one of the plaintiffs.

"It's a watershed moment," said Michael Bender of the Mercury Policy Project, another plaintiff.

Mercury is a well-known neurotoxin that can cause cognitive and developmental problems, especially in fetuses and children. It can also cause brain and kidney damage in adults.

In 2002, the FDA began a regulatory review of amalgam that was expected to be complete within a few years. In 2006, with the review still incomplete, an independent FDA advisory panel of doctors and dentists rejected the agency's position that there is no reason for concern about the use of amalgam. While the panel agreed that the majority of people receiving such fillings would not be harmed, panel members expressed concern for the health of certain sensitive populations, including children under the age of six.

The panel recommended that the FDA conduct further studies on the risks to children from dental amalgam, and that it consider a policy of informed consent for children and pregnant: that is, warning those groups of the risks associated with the fillings before installing them.

Part of the lawsuit centered on the FDA's failure to respond to these recommendations in a timely fashion.

"This is your classic failure to act," federal judge Ellen Segal Huvelle told the agency.

As part of the lawsuit settlement, the FDA must reach a final decision on the regulation of amalgam by July 28, 2009.