Across the United States, municipalities are working to reduce the discharge of mercury to wastewater treatment plants (WWTPs).  Mercury is a bioaccumulative toxic pollutant that can cause a variety of adverse health effects in humans.  In water, certain microorganisms can change mercury into methylmercury, a highly toxic form that builds up in fish, shellfish, and ultimately, humans.  For, municipalities, Kentucky’s water quality standard of 0.051 µg/l (5.1×10-5 mg/l) means that one elevated sample can potentially lead to a KPDES permit limit for mercury.

A 2003 study funded by the American Dental Association (ADA) estimated that dental offices contributed 50 percent of the mercury entering WWTPs.  Mercury-containing wastes can find their way into the environment when new fillings are placed or old mercury-containing fillings are drilled out and waste amalgam materials are flushed into chair-side drains.  Therefore, EPA is proposing technology-based pretreatment standards for discharges of mercury and other pollutants from dental practices.  EPA expects that nationwide compliance with the proposed rule will reduce the discharge of metals to WWTPs by at least 8.8 tons per year, half of which is mercury.

The proposed rule would allow dentists to demonstrate compliance by installing, operating and maintaining amalgam separators.  EPA estimates an average annual cost of $700 per dental office.  The proposed rule would also allow dental offices that have already installed amalgam separators that do not meet the proposed removal efficiency to still be considered in compliance for the life of the installed separator.

dental chair