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Water: Dental Amalgram

Dental Amalgam Effluent Guideline

EPA has submitted a draft proposed rule to the Office of Management and Budget for interagency review of pretreatment standards for existing and new dental practices that discharge dental amalgam to publicly owned treatment works (POTWs). EPA would also propose to amend selected parts of the General Pretreatment Regulations (40 CFR Part 403) to streamline oversight requirements for the dental sector. (May 29, 2014)


Across the United States, many states and municipal wastewater treatment plants (publicly owned treatment works) are working toward the goal of reducing discharges of mercury to POTWs.

Mercury is a concern to human health because it is a persistent bioaccumulative toxic element. Many studies have been conducted in an attempt to identify the sources of mercury entering these POTWs. According to the 2002 Mercury Source Control and Pollution Prevention Program Final Report prepared for the National Association of Clean Water Agencies (NACWA), dental clinics are the main source of mercury discharges to POTWs. A study funded by the American Dental Association (ADA) estimated in 2003 that 50 percent of mercury entering POTWs was contributed by dental offices. EPA estimates that dentists discharge approximately 4.4 tons of mercury each year to POTWs. EPA estimates there are approximately 160,000 dentists working in over 120,000 dental offices who use or remove amalgam in the United States – almost all of whom discharge their wastewater exclusively to POTWs.

Mercury-containing amalgam wastes may find their way into the environment when new fillings are placed or old mercury-containing fillings are drilled out and waste amalgam materials that are flushed into chair-side drains enter the wastewater stream. Some of the waste amalgam particles that reach the sewer system settle out in the sewers, and some are carried to POTWs. The physical processes used in POTWs remove about 90% of the mercury received in wastewater. The mercury removed from wastewater then resides in the biosolids or sewage sludge generated during primary and secondary treatment processes.

Memorandum of Understanding on Reducing Dental Amalgam Discharges

In December 2008, the Office of Water signed a Memorandum of Understanding (MOU) with the American Dental Association (ADA) and the National Association of Clean Water Agencies (NACWA) to establish and monitor the effectiveness of a Voluntary Dental Amalgam Discharge Reduction Program.

The purpose of this MOU is to have dental offices voluntarily install and properly maintain amalgam separators, and recycle the collected amalgam waste. EPA intends to continue outreach efforts under the MOU during the rulemaking process.

Resource Documents

You will need Adobe Reader to view some of the files on this page. See EPA's PDF page to learn more.

The following documents provide a resource to pretreatment programs and dentists that are looking to reduce the discharge of mercury amalgam in wastewater.

Additional Information/Contacts

For additional information regarding dental amalgam, please contact Damon Highsmith (highsmith.damon@epa.gov) or 202-566-2504.

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