The US Environmental Protection Agency (EPA) plans to propose a rule to reduce mercury waste from dental offices through the use of existing technology to capture dental mercury, meeting the proposed requirements.

Mercury in dental amalgams, or fillings, which account for 3.7 tons of mercury discharged from dental offices annually, is flushed into chair-side drains to enter the wastewater systems, making its way into environment through discharges to rivers and lakes and land application of sewage sludge.

The new rule, which is expected to be proposed next year and finalized in 2012, will require dental offices to use amalgam separators that are designed to capture the mercury, which is then recycled and reused.

Until the rule is final, EPA encourages dental offices to voluntarily install amalgam separators that are claimed to separate out 95% of the mercury normally discharged to the local waste treatment plant.

The new rule will enable dental offices to manage and prevent the amalgam discharges, which comprises 50% of mercury entering local waste treatment plants that convert into methylmercury, an environmental toxicant, through contact with some microorganisms.