has unveiled a new cause for concern: In the January 2006issue of EHP , child psychiatry professor Gail Wasserman and colleagues from Columbia University reported that Bangladeshi children who drank well water with high concentrations of naturally occurring manganese had diminished intellectual function. The researchers noted that the bioavailability of manganese in water is higher than that of manganese in food. They also pointed out that about 6% of U.S. wells have a high enough manganese content to potentially put some children at risk for diminished intellectual function. The cellular and molecular mechanisms of manganese neurotoxicity are not well understood. The dopaminergic system in the basal ganglia, which is affected in Parkinson disease, may be involved, but this hypothesis is controversial. Toma Guilarte, a professor of molecular neurotoxicology at the Johns Hopkins Bloomberg School of Public Health, described research on these systems in nonhuman primates at the XXII International Neurotoxicology Conference. According to Guilarte, unpublished positron-emission tomography studies of the basal ganglia show that manganese does appear to have an effect on dopaminergic neurons. Guilarte found that the more manganese the animals received, the less dopamine was released through the actions of amphetamine (which is used to induce the release of the neurotransmitter). This does not mean that manganese causes Parkinson’s disease, merely that it has an effect on those neurons, he says. This is the first report of an in vivo effect on dopamine release by manganese.