Dental chair a possible source of neurotoxic mercury waste

The finding raised the question whether the culprit bacteria were living in the mouths of dental patients. "We don't have the answer," Rockne said.

Based on their sample studies, the researchers estimate that 2-5 kilograms, or up to 11 pounds, of methyl mercury could be entering the public water supply of the United States each year from dental waste water. While this may not seem like much, methyl mercury is highly toxic in minute amounts.

When in waterways, methyl mercury tends to get biomagnified up the food chain, moving from algae and phytoplankton to fish and, ultimately, to humans.

While surprised by the level of contaminants found in the study, Rockne says follow-up research is necessary -- then, possibly, some basic engineering.

"Amalgam separators are a good first step, but maybe something else is necessary downstream to prevent further methylation and prevent further soluble mercury from getting through the system," he said.

"We have to take more steps to prevent the problem from occurring in the first place," he said. "We're dealing with a pipe -- a control point. As an engineer, I see this as a problem that is tractable -- something we can definitely do something about."

Other researchers in the study include UIC environmental engineering Ph.D. student Xiuhong Zhao and orthodontics resident Ryan Hurley. Measurements of methyl mercury were performed using a technique developed at UIUC's department of natural resources and environmental sciences. Contributing department members were Robert Hudson, associate professor, and graduate student Christopher Shade.

Funds were provided by the National Science Foundation and the National Institutes of Health.