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Mercury Not Necessarily Sickening Dentists

Study finds higher levels, but no proof of ill effects

TUESDAY, April 30, 2002 (HealthDayNews) -- Dentists who regularly use mercury fillings have higher levels of the heavy metal in their bodies, but a new Scottish study finds no conclusive proof that it's making them sick.

The dentists surveyed did report having more illnesses, such as memory problems and kidney disorders, which are associated with mercury exposure. While the authors say the link is circumstantial, they add the dentists should be monitored more closely.

However, critics complain the study is flawed.

Ewan B. Macdonald and his colleagues from the University of Glasgow compared 180 practicing dentists with 180 faculty members who had nothing to do with dentistry. Both groups were asked to give urine, hair and nail samples so they could measure residual mercury levels. They found out how many hours a week the dentists worked, and how many mercury fillings they typically handled.

The practicing dentists had higher levels of mercury in their hair and nail samples -- and more than four times the levels of mercury in their urine -- than did the academics. Only one dentist, however, had urinary levels above the government-recommended threshold, the researchers report in the May issue of Occupational and Environmental Medicine.

While the practicing dentists reported more kidney disorders and memory problems than did the academics, the conditions were not found to be directly related to higher urinary mercury levels.

"Our study did not show significant effects on dentists compared to controls, and none required medical interventions as a result of our study," Macdonald says. "In many respects, our study did not show that they were different from controls."

Even so, the authors say similar health effects, such as kidney and memory problems, have been associated with mercury exposure, and they call for continued health surveillance of dentists who use mercury.

"There is no reason for patients to be concerned on the basis of this study," Macdonald stresses.

Critics on both sides of the mercury debate say the study is poorly designed and conducted.

In an editorial accompanying the study, Diana Echeverria, a senior scientist at Battelle's Center for Public Health Research and Evaluation in Seattle, takes issue with the choice of the control group.

"I think the study has flaws," she says. "Had they used a different control group, they may in fact have found a significant effect [of the mercury exposure]."

The researchers also did not control how reliable the subjects' memories were before the study. "The study isn't bad, but it's incomplete," she says.

Echeverria, a veteran researcher on the health effects of dental amalgam, says she believes the possibility of patients and dentists experiencing difficulties such as a memory problem because of amalgam fillings is "present, but mild." And many of the problems she believes are associated with dental amalgam, she says, are reversible. Some problems are not likely to even be noticed by patients.

Likewise, the American Dental Association (ADA) says the study's design is faulty. The ADA has also studied dentists and their mercury levels, and has not found problems, says Chakwan Siew, director of toxicology for the ADA Health Foundation Research Institute. The institute screens about 1,000 dentists each year.

"We found with dentists who practice good mercury hygiene [such as using pre-encapsulated mercury] that the concentration of mercury in the urine of dentists is not different than that of the general population," Siew says.

While acknowledging there are individuals who are "hypersensitive" to mercury in silver fillings, the ADA generally views dental amalgams with mercury as safe.

The organization is hotly opposing a House bill that would ban the use of mercury amalgams by 2007.

What To Do

Read a consumer update on dental amalgams from the U.S. Food and Drug Administration. You can also check out the American Dental Association's opposition to the bill that would outlaw mercury fillings.

Learn more about mercury and its effects from the Environmental Protection Agency.

SOURCES: Ewan Macdonald, senior lecturer, occupational health, University of Glasgow, Glasgow, Scotland; Chakwan Siew, Ph.D., director, toxicology, American Dental Association's Health Foundation Research Institute; Diana Echeverria, Ph.D., senior scientist, Batelle Center for Public Health Research and Evaluation, Seattle; May 2002 Occupational and Environmental Medicine
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