Be careful where you spit those old fillings.

• Position: Mercury Contamination - Brief article

Standards to help cut discharges of dental amalgam into the environment have been proposed by the Environmental Protection Agency under the Clean Water Act. Amalgam is a mixture of mercury and other metals that dentists use to fill cavities. Mercury is discharged when dentists take out old fillings or remove excess amalgam when placing a new filling.

Studies show about half the mercury that enters Publicly Owned Treatment Works (POTWs) comes from dental offices. Mercury from amalgam then can make its way into the environment in a number of ways, including through discharge to water bodies. Contact with some microorganisms can help create methylmercury, a highly toxic form of mercury that builds up in fish, shellfish, and fish-eating animals. Fish and shellfish are the main sources of human exposure to methylmercury.

In response, many states and localities have implemented amalgam discharge-cutting programs requiring amalgam separators and other Best Management Practices in dentist offices. The American Dental Association also recommends separators and other Best Management Practices for...