Mercury in dental amalgams may pose health risks to children, fetuses and pregnant women, the U.S. Food and Drug Administration is warning.

The FDA issued a statement, on its website Wednesday, about the potential dangers of dental amalgams.

As part of a legal settlement reached Monday, the federal agency has agreed to release a new ruling on the safety of dental amalgams in July 2009, and alert consumers about potential related hazards. Consumer advocacy groups, including Moms Against Mercury, called for a ban on the fillings in the U.S.

"Dental amalgams contain mercury, which may have neurotoxic effects on the nervous systems of developing children and fetuses," the FDA said.

"When amalgam fillings are placed in teeth or removed from teeth, they release mercury vapour. Mercury vapour is also released during chewing."

The FDA says consumers should not have amalgam fillings removed.

Health Canada says that while amalgam has been shown to release mercury in the body, the levels are not serious enough to cause adverse health effects.

The federal agency says current data does not support hypotheses linking mercury exposure with Alzheimer's disease, amyotrophic lateral sclerosis, multiple sclerosis and Parkinson's disease.

But the federal agency notes patients with kidney disease and pregnant women should avoid dental amalgams given that mercury has been shown to cross the placental barrier and weaken kidney function at sub-clinical levels of exposure.

Sweden and Norway have banned the use of dental amalgams, citing health concerns.