2 new studies found that amalgam fillings can be used safely, without harming the body. The present research reported high levels of mercury in the urine of the children who received amalgam fillings, but no harmful effects were found on the children's kidney function or their neurological capacities. In the first study, 534 children from 6 to 10 years old received mercury containing amalgams or resin composite and, after 5 years, reporting no differences in neurophysiological or renal functions. The second study looked at 507 children ages 8 to 10 having implanted mercury-based fillings or resin-based fillings and, after monitoring them for 7 years, no measurable differences were found between the 2 groups."We saw no observable differences in neuropsychological or kidney outcomes. I think the findings should be fairly reassuring," said the lead author of one of the studies, David Bellinger, a professor of neurology at Harvard Medical School. "We can't reject the hypothesis that there is a sensitive subgroup that may confer a little more vulnerability [to mercury in fillings]," he added. Amalgam fillings contain about 50% mercury. Though health experts say that it does not pose a health risk, consumer groups tend to disagree, asserting that mercury, known as a neurotoxin, can leak out in the form of mercury vapor, getting into the bloodstream. "Given the numbers of children exposed to dental amalgam, it is critical that further rigorous studies examine the molecular effects of the toxicant at appropriate doses, measure exposure as precisely as possible, and explore the important question of vulnerability factors," said in his editorial Herbert L. Needleman, of the University of Pittsburgh School of Medicine.