The US Environmental Protection Agency (EPA) today proposed standards under the Clean Water Act to help cut discharges of dental amalgam to the environment. Amalgam is a mixture of mercury and other metals that dentists use to fill cavities. Mercury is discharged when dentists remove 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 can then 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 (ADA) also recommends separators and other Best Management Practices for amalgam.

EPA expects compliance with this proposed rule would cut metal discharge to POTWs, half of it from mercury, by at least 8.8 tons a year.

“This is a common sense rule that calls for capturing mercury at a relatively low cost before it is dispersed into the POTW,” said Kenneth J. Kopocis, deputy assistant administrator for EPA’s Office of Water. “The rule would strengthen human health protection by requiring removals based on the use of a technology and practices that approximately 40% of dentists across the country already employ thanks to the ADA and our state and local partners.”

This action also represents one way that the United States is meeting the goals of the Minamata Convention on Mercury, an international environmental agreement that addresses human activities contributing to widespread mercury pollution, which impacts the American public. EPA’s proposed rule supports a Convention measure to promote the use of best environmental practices in dental facilities to reduce releases of mercury compounds to water and land.

The proposed rule would require all affected dentists to control mercury discharges to POTWs. Specifically, it would require them to cut their dental amalgam discharges to a level achievable through the use of the best available technology (amalgam separators); and the use of other Best Management Practices. The proposed rule would allow dentists to demonstrate compliance by installing, operating, and maintaining amalgam separators. It would declare dental practices whose existing separators do not remove the percentage of amalgam in the proposed requirements as meeting the proposed requirements for the life of the existing separator. Finally, it would limit dental dischargers’ reporting requirements to annual certification and recordkeeping in lieu of wastewater monitoring.

The EPA is also proposing to streamline dental sector oversight requirements to cut implementation and oversight costs of the proposed rule to states and localities by $47 million annually.

The agency will accept public comments on the proposal for 60 days following publication in the Federal Register. A public hearing is also scheduled for November 10 at 1 pm in the William J. Clinton East Building, Room 1153. The agency expects to finalize the rule in September 2015.