The report, released by a group of American environmental and health groups, known as Health Care without Harm, says dentists are now the largest single contributors of wastewater mercury in the country.

Against a background of declining mercury use elsewhere, America’s 150,000 dentists are now the third-largest consumers of mercury in the country, using 41 tonnes of the metal in 100 million fillings each year. Most of that eventually finds its way into the environment by being rinsed down the drain, deposited in biomedical waste containers destined for incineration, or by being placed in municipal waste landfill, the report maintains.

“While many other industries are phasing out the use of mercury products, dentists continue to use large amounts of mercury and dispose of it improperly,” said Michael Bender, author of the report and director of the Mercury Policy Project.

Mercury makes up about half of the amalgam used in ‘silver’ fillings. Although it is generally thought to be safe in teeth, once the amalgam is released into water and soil it is transformed into highly toxic methyl mercury, says the report.

The compound accumulates in the tissue of living organisms, becoming more concentrated higher up the food chain. Pregnant women and predatory animals are particularly at risk. According to a 2001 report by the US Centers for Disease Control, one in 10 US women of child-bearing age is exposed to potentially dangerous levels of mercury (see related story).

A statement from the American Dental Association (ADA) in response to the report said its members were committed to providing dental care in “an environmentally responsible manner”. The Association also pointed out that it has developed a comprehensive action plan to address amalgam in dental wastewater, which includes an assessment of mercury release and of the effectiveness of current amalgam reduction technology.

The organisation also claims that a 1996 study found that when amalgam particles were subjected to simulated wastewater treatment processes, no soluble mercury was detected, even at a concentration of one part per billion.

Nevertheless, the ADA states that it will continue to actively address the issue of amalgam in dental wastewater.

However, Bender is less convinced of the sector’s good will towards environmental protection, describing their assertion that amalgam causes no environmental impact as being based on “questionable scientific assumptions”. Devices exist which are capable of extracting the mercury particles from wastewater so that they can be recycled, but the report accused the ADA of obstructing efforts to require dentists to fit the separators, which cost between $50 and $100 a month to operate.

“Despite substantial scientific evidence that mercury is dangerous to the environment and human health, the American Dental Association is actively working against safety measures that would require dentists to trap and recycle this toxic metal, said Bender. “They’re attempting to get state legislation vetoed,” he told edie.

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