Sept. 7, 2006 -- A federal advisory panel today rejected the FDA's conclusion that mercury in dental fillings poses little or no health risk to patients.
Experts said the move does not reflect a concern that mercury in fillings poses a risk to the vast majority of the tens of millions of Americans who have them.
Instead, the advisory panel warned that available scientific studies have not gone far enough to explain apparent health reactions seen in a minority of patients.
Prolonged or excessive mercury exposure can cause neurodevelopmental deficits in children, such as lower IQs or nerve problems, as well as neurologic problems in adults.
But dentists have long believed amalgam fillings (which contain mercury in addition to other metals) don't expose most patients to significant mercury levels.
Reports from the Environmental Protection Agency in 1993, and the U.S. Public Health Service in 1997, concluded mercury in fillings causes no serious health risks to patients.
A draft FDA report, issued this week, backed up those conclusions, saying no new information has come to light to refute them.
But experts on the advisory panel Thursday voted 13 to 7 to reject that conclusion because gaps in the scientific data leave open some questions about the fillings' safety.
For example, researchers have not determined whether mercury fillings are more dangerous for pregnant women and their newborns than for adults.
Studies have only just begun to tease out how much mercury humans get from dental fillings versus other environmental sources such as workplace exposure and eating contaminated fish.
Dozens of activists complaining of bad health effects testified before the committee over two days of deliberations.
"The vast majority of the population ... is extremely unlikely to have any complication," says Karl D. Kieburtz, MD, who co-chaired the panel. But available scientific studies make it difficult to determine "what population might be at what risk," says Kieburtz, a professor of neurology and preventative medicine at the University of Rochester School of Medicine and Dentistry.
Studies also have not determined why a small minority of patients may accumulate higher mercury levels than others even after similar levels of exposure.
"I'm taking it more seriously that there could be exposures, acute exposures," says Lynn R. Goldman, PhD, a professor of environmental health sciences at Johns Hopkins University in Baltimore, Md.
Two studies of 534 American children and 507 Portuguese children, published in the April issue of JAMA, The Journal of the American Medical Association, found no appreciable effect of amalgam fillings on a battery of neuropsychological tests, IQ tests, and nerve tests.
But European studies that suggest high mercury levels in some filling wearers have gained increased scrutiny from regulators there.
The FDA recently recommended that children and women of childbearing age limit their consumption of tuna and other kinds of fish because of high mercury levels in certain fish.
And activist groups have sought to ban mercury fillings, calling them unsafe.
The advisory panel made no official recommendations after its meeting. FDA officials will now have to rethink how to address public concerns about mercury fillings.
"We will take your recommendations, and we will start evaluating the next steps of what we do," Norris D. Alderson, MD, the FDA's associate commissioner for science, told the panel.
Readers with concerns about their fillings should talk to their dentist.