Inside Dentistry
July 2019
Volume 15, Issue 7

Plan Ahead for Amalgam Discharge Compliance

Are you up-to-date on best management practices?

Apersistent pollutant with well-documented effects on human health, mercury is of particular concern to the dental community. In 2003, a study by the American Dental Association (ADA) estimated that 50% of the mercury entering publicly owned treatment works (POTW) facilities was contributed by dental offices. Since the late 1970s, the use of dental amalgam has decreased as the use of materials such as composite resins and glass ionomers has steadily increased. It is estimated that the incidence of placing dental amalgam has been reduced by 2% to 3% per year. Based on this information, the Environmental Protection Agency (EPA) estimates that the mercury in dental amalgam discharges to POTW facilities will decrease by about half within the next 25 years. However, although the use of dental amalgam continues to decline, EPA estimates that approximately 2 tons of mercury will continue to be discharged to POTW facilities in 2040. Approximately 103,000 US dental offices use or remove amalgam, and almost all use POTW facilities.

Mercury enters dental wastewater in many forms. Although POTW facilities have a 90% efficiency rate in removing the material, a small amount of waste amalgam is released into area surface waters. It can also make its way into the environment through the incineration, land filling, or land application of sewage sludge.

ADA directs dental practices to manage waste in a manner consistent with the association's Best Management Practices for Amalgam Waste, which were developed to reduce the amount of mercury entering the environment. In 2017, EPA issued a final rule, Effluent Limitations Guidelines and Standards for the Dental Category (40 CFR 441), to reduce discharges of mercury and other metals from dental offices into POTW facilities. The rule requires dental offices to comply with requirements that are based on the ADA's best management practices, including the use of amalgam separators.

Amalgam separators are solid collectors that capture and remove amalgam and other particles in the dental waste stream through the process of sedimentation, filtration, centrifugation, or a combination of these mechanisms. Under the rule, the equipment used needs to be compliant with either the American National Standards Institute's American National Standard/American Dental Association Specification No. 108 for Amalgam Separators (2009) with Technical Addendum (2011), the International Organization for Standardization's 11143 standard (2008), or subsequent versions that require amalgam separators to achieve at least 95% removal efficiency. The amalgam separator(s) must be inspected in accordance with the manufacturer's operating manual to ensure proper operation and maintenance and to confirm that all wastewater from processes involving amalgam is flowing through the amalgam-retaining portion.

The rule applies to all dental practices, including large institutions such as dental schools and clinics, that discharge to a POTW. Dental offices that discharge to POTW facilities but do not place or remove amalgam need only submit a onetime certification. In addition, dental dischargers that do not place or remove amalgam except in limited emergencies or unplanned, unanticipated circumstances are exempt from any further requirements if they certify as such in a onetime compliance report to their control authority.

Dental offices that place or remove amalgam must operate and maintain an amalgam separator and must not discharge scrap amalgam or use certain kinds of line cleaners. They must also submit a onetime compliance report to their control authority. The control authority can be a local wastewater utility, a state environmental agency, or a US EPA regional office. For dental offices in Alabama, Connecticut, Mississippi, Nebraska, or Vermont, the control authority is the state agency. Dental offices in all other states should contact the EPA regional office, local wastewater utility, or state agency pretreatment coordinator to find out who their control authority is.

Existing dental offices that were discharging into POTW facilities prior to July 14, 2017, must be in compliance with the standards by July 14, 2020, and submit a onetime compliance report certifying as such by October 12, 2020. New sources (ie, those whose first discharge to a POTW occurred after July 14, 2017) must be in compliance with the standards immediately and submit a onetime compliance report certifying as such within 90 days.

The Effluent Limitations Guidelines and Standards for the Dental Category is a minimum requirement, and there may be additional requirements under state or local laws that go beyond those of the EPA rule. The EPA expects that compliance with this final rule will annually reduce the discharge of mercury by 5.1 tons, as well as 5.3 tons of other metals found in discharged waste dental amalgam.


Effluent Limitations Guidelines and Standards for the Dental Category

Technical and Economic Development Document for the Final Effluent Limitations Guidelines and Standards for the Dental Category

Amalgam Separators and Waste Best Management

Fact Sheet: Effluent Limitations Guidelines and Standards for
Dental Offices

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