Down the drain
By: Amanda Smith-Teutsch
June 07, 2010

While both the U.S. government and the American Dental Association want to reduce the amount of mercury that dental patients spit out in the dentist’s drain, the ADA is urging a voluntary, nonregulated approach to the problem.

The Domestic Policy subcomittee of the House Committee on Oversight and Government Reform held hearings May 26 to examine a voluntary agreement proposed by the U.S. Environmental Protection Agency and the National Association of Clean Water Agencies to reduce mercury from dental waste that winds up in the environment.

While coal burning power plants are the largest source of mercury in the environment, the U.S. government recognizes incinerators, automobiles and industrial boilers as the No. 2 source of mercury pollution. At the hearing, subcommittee chairman Dennis Kucinch said the dental industry is an unrecognized member of this second-tier source of pollution.

“Currently, dentists use more than 20 tons of mercury per year in dental fillings, replacing or repairing current fillings or putting new fillings in,” the chairman said in his opening remarks. “Where does all the waste mercury go? Often it goes down the drain.”

Once in the municipal wastewater system, mercury can find its way into the environment through several outlets, including sewer overflows and incineration of biosolids sludge. When a person’s body is cremated after death, Kucinich said, mercury from their dental fillings can be released into the air.

Currently the EPA estimates less than one ton of mercury per year is emitted into the air through incineration of sewer sludge or crematoria; however, recently the agency has said its measurements may only represent a fifth of actual emissions, Kucinich said.

He expressed disapproval of the voluntary agreement.

“If EPA has underestimated the extent of the environmental problem caused by dental mercury, it has also overestimated the amount of cooperation dentists have voluntarily given toward preventing amalgam from leaving dental offices in waste water,” he said. He also said EPA data from crematoria were based on tests conducted 10 years ago at a single location, and said previous hearing testimony said mercury air emissions connected to the dental industry could be has high as 7 to 9 tons per year.

While mercury from dental waste is a small percentage of the overall source of pollution, the impact can be larger on a local level, said EPA Deputy Assistant Administrator for Water Nancy Stoner, who testified at the hearings.

“At the local level data indicate that discharges from dental facilities can be a significant contributor to mercury in the environment,” she said.

There are several steps dental offices can take to keep mercury-containing dental waste out of the local environment, she said, including capture of drilled amalgam from chair-side drains and sinks, traps and filters and other wastewater treatment options. Current “best practices” recommended by the American Dental Association call for the use of amalgam separators to capture mercury-containing waste particles, she said, and the EPA is encouraging dentists to use mercury-free fillings in their practices.

William J. Walsh, speaking for the American Dental Association, said the ADA was committed to increasing the use of separators to capture more mercury-containing waste before it entered municipal water treatment systems and proposed a voluntary 65% increase in use of the devices at its member dentistry offices within two years. He urged the government to avoid setting limits on discharges.

“This is very ambitious, but we are committed to it,” Walsh said. “The ADA has devoted substantial time and resources to promoting its best management practices. Dentistry is proud of all its efforts to protect the environment.”

He pointed out that many dentists are already phasing out the use of mercury-containing fillings.

Regulating mercury waste discharges would result in significant expense to the government and to dentists, and eventually to taxpayers, he said.

John Reindl, speaking for the Mercury Policy Project, urged for increased government control of mercury waste at the dental offices, saying the EPA and the ADA were understating the impact of the discharges.

“The dental sector also remains the largest mercury contributor to waste water by far,” Reindl said. “Although they are decreasing they are still large users.”

The project recommended tight controls on mercury disposal at dental offices and on mercury emissions at crematoria.

As better access to dental care results in higher retention of teeth at death, Reindl said more fillings are present in corpses sent to crematoria. Cremations have steadily increased over the past decade, and are expected to double to 1.5 million cremations annually by 2020, he said. A 2003 study in the United Kingdom found mercury emissions increased 42% per cremation, based on the number of teeth and dental fillings per corpse, he said.

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