The common dentist office practice of flushing old mercury-containing fillings down the drain makes dentists the single largest discharger of the toxic metal into the nation's wastewater treatment plants, according to a national study by a Boston-based public health group. Most of the mercury is eventually discharged into bodies of water.
In a time that everyone from hospitals to coal-burning power plants are taking steps to reduce emissions of mercury, Health Care Without Harm, along with other environmental groups, is calling on dentists to follow suit. US dentists still use about 40 tons a year of mercury to make silver fillings. While the fillings may be fine for years in people's mouths, the report sponsors' say, they spend a much longer time in the environment, where they can break down.
''In the last seven years, hospitals in Greater Boston have reduced mercury pollution,'' said Bill Ravanesi, campaign director of Health Care Without Harm, one of the seven sponsors of the report ''Dentist The Menace?'' He is calling for dentists to use separation devices to capture the mercury before it is washed away.
''Everyone is doing their part, but the dental industry hasn't reduced their pollution at all,'' Ravanesi said.
Mercury is a naturally occurring metal, but it can do nerve and brain damage in certain forms and harm fetuses if pregnant women ingest it. Alice in Wonderland's ''Mad Hatter'' was based on milliners who suffered from mental problems after using mercury to soften felt.
For the past 150 years, dentists have used an inexpensive and durable amalgam of mercury, silver, tin, copper, and zinc to fill cavities, with mercury as the main ingredient. Critics for years have argued that people with mercury fillings can become ill, but the scientific community still considers the fillings safe to use.
Although some dentists still use mercury-based fillings, the use of white plastic composites is increasing.
There has been little discussion on the dangers of washed-away fillings until now. Yesterday, American Dental Association officials said the fillings pose little danger to the environment because the alloy doesn't break down. Officials there said they don't oppose in-office devices to prevent mercury from going down the drain, but said it's hardly necessary.
''It's a very stable material,'' said Dan Meyer, director of science for the American Dental Association. ''We have an ethical and moral obligation to do good, and we would never do anything to cause harm to the public.''
Still, the report's sponsors, who include the Mercury Policy Project in Vermont and Clean Water Action in Boston, say evidence exists that the alloy does break down, releasing mercury into the environment. For around $50 a month, the report's author estimates, dentists could capture and recycle the mercury from old fillings.
''It can cost the price of a filling each month to fix,'' said Michael Bender of the Mercury Policy Project and author of the report.
New England is now one of the most aggressive in reducing mercury use. Two years ago, New Hampshire became the first state in the country to ban the use of mercury in thermometers. Last summer, Massachusetts public health officials urged young women and children under age 12 to stop eating most fish from the state's lakes and streams. Meanwhile, a first-of-its-kind mercury law in New Hampshire calls for rules for dentists to trap their mercury.
In 1985, dentists were about the sixth-largest user of mercury, behind batteries and factories that use it to produce chlorine, paint, and measuring instruments, according to the report. Now, with mercury in many products outlawed, phased-out, or reduced, dentists are the third-largest user of mercury, behind the makers of wiring devices and switches, and chlorine. The report says dentists use about 44 tons of mercury each year, most of which is eventually released into the environment.
''To me, it's plain and simple,'' says G. Robert Evans, a dentist with West Newton Dental Associates. Evans said he gave up using mercury in fillings close to 20 years ago. ''It's going to accumulate in the environment if we don't keep it out. So I keep it out.''
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