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Water: Dental

Dental Effluent Guidelines

new icon Extension of comment period to February 20, 2015

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EPA is proposing technology-based pretreatment standards for discharges of pollutants into publicly owned treatment works (POTWs) from certain existing and new dental practices.  The proposal would require such dentists to comply with requirements for controlling the discharge of dental amalgam pollutants into POTWs. The requirements are based on the best available technology or best available control technology, amalgam separators, and Best Management Practices.  EPA is also proposing to amend the General Pretreatment Regulations (40 CFR Part 403) to streamline oversight requirements for the dental sector.

Public Comments

EPA is requesting comments on this proposal. Comments must be received no later than February 20, 2015. This is a 60 day extension from the original deadline of December 22, 2014 in response to numerous requests for an extension. Please see the October 22, 2014 Federal Register notice for instructions on submitting comments.

Public Hearing

EPA conducted a public hearing on the proposed pretreatment standards on November 10, 2014. A transcript of the hearing is available (PDF) (63 pp, 271K) and has been added to the rulemaking record.

Background

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 percent 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 EPA signed a Memorandum of Understanding (MOU) with the ADA and 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

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

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

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