Dentists urged to do more to curb mercury pollution. But industry says disposal of amalgam filling waste poses little danger

Wednesday, June 5, 2002

By LISA STIFFLER
SEATTLE POST-INTELLIGENCER REPORTER

http://seattlepi.nwsource.com/local/73339_mercury05.shtml

Dentists can ease the pain of an aching tooth, but they're hurting the environment when they flush old mercury-based fillings down the drain, according to a national study.

Dental offices in Washington state and across the country are releasing large amounts of mercury into the air and water by failing to properly capture and dispose of waste from "silver" amalgam fillings, the study's authors said yesterday.

Health Care Without Harm and other environmental groups sponsoring the report are calling on dentists to follow the example of hospitals and coal-burning power plants, both of which have reduced mercury emissions.

King County is ahead of many metropolitan areas -- requiring by July 2003 that dental offices install better devices for trapping amalgam waste -- or prove they're not polluting.

"We have had a number of calls from dentists that are happy with what we're doing," said Elsie Hulsizer, King County's industrial-waste supervisor. "We don't want to make dentists look like evil polluters here. It's just their time to get into compliance."

The table above shows preliminary data on the leading sources of mercury pollution in Washington State.  Information for the article was taken from the Draft for Public Comment: Washington State Mercury Chemical Action Plan (http://www.ecy.wa.gov/pubs/0203042.pdf) provided by the Washington State Department of Ecology (http://www.ecy.wa.gov/programs/eap/pbt/pbtfaq.html).

The state Department of Ecology is setting guidelines for reducing industrial and residential mercury pollution, including contributions by dentists.

This fall, the Washington State Dental Association will decide whether to formally encourage its members to install amalgam separators, which capture the smallest amalgam "dust" in a settling tank.

Dentists are the largest single source of mercury that ends up at wastewater-treatment plants, said Laurie Valeriano, policy director for the Washington Toxics Coalition.

"It's a serious concern for Washington state," she said. "We have fish advisories for mercury contamination."

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.

There has been concern raised that amalgam fillings can sicken people, but scientific evidence proving that the fillings are dangerous is lacking and major health organizations still consider the treatment safe.

American Dental Association officials and Seattle dentists say the fillings pose little danger to the environment because the alloy doesn't break down.

"The problem has to be put in perspective," said Victor Barry, a dentist on Seattle's First Hill and past president of the state dental association. "Dentists have been given an unfair focus on the issue."

Nationally, dental organizations say their mercury use is down 90 percent over the past 30 years. More people are opting for glass and acrylic "composite" fillings that look more natural than the silver amalgam fillings. And people have fewer cavities because of improvements made in oral health-care.

"There just is not as much amalgam being used," said David Hemion, assistant executive director of the Washington State Dental Association.

But the national report says dentists still use about 44 tons of mercury each year, most of which is eventually released into the environment.

Once in the environment, mercury is converted into a more toxic form that moves up the food chain. It can accumulate in the part of the brain responsible for motor function. Pregnant women exposed to high levels of the toxic substance can have babies with severe motor impairment, paralysis and numbness.

The Food and Drug Administration, U.S. Environmental Protection Agency and state Health Department have warned women of childbearing age and children under age 6 to limit consumption of fish, particularly bottom-feeding fish and tuna.

As an industry, dentistry ranks third in terms of mercury consumption in this country, behind producers of wiring and electrical switches that use mercury and certain chlorine manufacturers.

And amalgam remains a significant source of mercury pollution in Washington.

An estimated 200 pounds of mercury is released annually from dental offices in King County, according to an October 2000 report by the county's Hazardous Waste Management Program.

Dental offices have filters for trapping the amalgam waste, but only separators capture the smallest particles. The King County study also found that less than half of the dentists surveyed properly disposed of the waste by turning it over to hazardous-waste recyclers.

Instead, it goes into landfills, is incinerated as medical waste, allowing it to escape into the air, or it flows into wastewater. At the treatment facilities, it generally winds up in sludge that is spread over forest and farmlands.

Despite those concerns, the level of mercury in treated sewage in King County is below 3 parts per million, considerably below the federal limit of 17 parts per million, county officials said.

The national report also raised concerns about mercury trapped in dental office plumbing. The authors recommend that contaminated plumbing be cleaned and replaced.

There is some debate as to the impact of the mercury in amalgam fillings when it escapes to the wastewater.

Some in the field of dentistry say it stays bound with the other filling components and is unlikely to become converted to methyl mercury -- the toxin associated with tainted fish.

Environmentalists claim there is evidence that bacteria do convert the compound into a form of mercury that is "bio-available," or able to enter the food chain where it can sicken humans.

Government officials say more information is needed, but are erring on the side of environmental caution.

"Once you put it into the environment, all kinds of things can happen," said Hulsizer. "We don't know as much about what happens in the environment as we would like to."

P-I reporter Lisa Stiffler can be reached at 206-448-8042 or lisastiffler@seattlepi.com