Tip Sheets

What you should know about the state of safe disposal of dental mercury

Mary Otto

By Mary Otto

Dental amalgam is the material at the center of the National Resources Defense Council’s mercury rule lawsuit.

It is a mixture of mercury and powdered metals, such as silver, tin, copper and zinc, that is defined and regulated as a medical device by the U.S. Food and Drug Administration (FDA).

While dental amalgam has been found to emit low levels of mercury vapor, it is considered safe for most dental patients over the age 6. The current FDA rules on amalgam safety date from 2009. However, health officials worldwide long have had serious concerns about the environmental impact when amalgam waste is disposed of after a procedure.

The United Nations in 2013 backed the Minamata Convention on Mercury, which set goals for reducing the amount of mercury released into the environment by mining operations, power plants, and businesses such as dental practices.

The U.S. Environmental Protection Agency (EPA), which says dental offices are the primary source of mercury discharge into water treatment systems nationwide, determined that dental amalgam waste can end up in sludge that is incinerated or deposited in landfills. Those practices enable mercury to leak into the air, water and soil, where combined with bacteria can form methylmercury, a neurotoxin.

Methylmercury can show up at dangerous levels in the food supply in fish and shellfish, according to this EPA explainer on mercury in dental amalgam. In this other resource, the EPA explains more about the impacts of methylmercury on human health. The dangers of amalgam waste entering the environment are related to how the human body processes and retains mercury in its different forms, according to researchers. The FDA offers an explanation in this fact sheet. Here is an excerpt:

Is the mercury in dental amalgam the same as the mercury in some types of fish? “The form of mercury associated with dental amalgam is elemental mercury, which releases mercury vapor. The form of mercury found in fish is methylmercury, a type of organic mercury. Mercury vapor is mainly absorbed by the lungs. Methylmercury is mainly absorbed through the digestive tract. The body processes these forms of mercury differently and has different levels of tolerance for mercury vapor and methylmercury.”

To address the problem of amalgam waste in the environment, the EPA announced new regulations in December that would have required dentists to install amalgam separators designed to capture the mercury so it could be recycled rather than flushed.

The agency’s dental effluent guidelines explain the preferred disposal process. Here is a prepublication version of the new final rule signed by then EPA Administrator Gina McCarthy on Dec. 15.

Implementation of the rule has been delayed pending the Trump administration’s initiative to reduce the government’s regulatory oversight.