More MS news articles for May 2002

Debate over mercury rising: Scientists are trying to get to the root of the controversy over the silver fillings

Tuesday, May 28, 2002 - 12:00 a.m. Pacific
By Carol M. Ostrom
Seattle Times staff reporter

Do "silver" fillings made from an amalgam of metals, including elemental mercury, a toxic substance poison your body?

There is little agreement between the most extreme sides of this fight.

One side would have you believe that mercury amalgam fillings are responsible for a host of ailments from Alzheimer's disease to multiple sclerosis.

Frankly, anti-amalgamists often sound a little out there. At a recent King County Board of Health hearing, for example, one woman testified that no one in her family can get along "because of mercury poisoning."

The other extreme insists amalgam is totally safe. To critics, they're the "ostrich" types, burying their heads in the sand and refusing to worry until proof whacks them in, well, the teeth.

Around the country, lawsuits and countersuits have been filed, bills introduced, including several in Washington state, and, in California, a dental board dissolved over the issue. In Oregon, an anti-fraud rule that prohibited dentists from pushing patients to remove properly functioning amalgam fillings was recently rescinded.

In the middle of this vociferious debate are many dentists, patients and scientists, trying to discover the truth about this widely-used filling material and its effect on health. For the approximately 100 million people in the world with mercury amalgam fillings not including the children whose cavities will need to be filled the issue is more than abstract.

Almost 80 percent of dentists say some patients have requested removal of amalgam fillings for nonaesthetic reasons, according to a survey by Dental Products Report, which regularly surveys a random sample drawn from nearly every dentist in the country. Last year, 24 percent said they don't use the fillings at all up from 10 percent in 1997.

Several countries have asked dentists to seek alternatives to mercury amalgam. Canada's official health agency says it's safe for most people, but has recommended that dentists forgo the fillings for pregnant women and consider other materials for children.

A short primer on the facts:

Dental amalgam is made up of mercury (about 43 to 50 percent by weight) mixed with silver, tin, copper and a dollop of zinc. In similar formulations, it has been used for about 150 years to fill cavities. It is considerably less expensive than alternatives and holds up reasonably well to chomping and chewing.

There are alternatives, but they're more expensive, trickier to install and, with the exception of gold, don't last as long. Some scientists say there's not enough long-term research on some of the newer alternatives, such as resin composite, which contain substances that may cause harm. (See the chart for more details on pros and cons of alternative fillings and amalgam).

Mercury is toxic in large doses. The "Mad Hatter" of Alice in Wonderland fame was inspired by 19th century milliners who used mercury to soften felt and were known for their dementia.

But mercury is also ubiquitous in the natural world it's found in the ocean and the Earth's crust. Mercury concentrates in fish tissues and moves up the food chain.

Established safe limits for mercury exposure are well above those measured in the general population (including those people with a number of mercury fillings), scientists say. But no one can say for sure that subtle effects don't occur at very small levels.

Amalgam fillings emit mercury vapor. Two decades ago, scientists were sure amalgam fillings were inert and that no vapor wafted from fillings. Today, they're sure they were wrong.

Dr. Michael Martin, a University of Washington researcher conducting a large, long-range study to measure effects of mercury amalgam fillings, told the county board of health: "We now know (mercury vapor) does in fact come out of mercury amalgams."

To some, that's enough to decide the issue. "There is no logical or commonsensical way to support the implanting of a deadly poison in the human body," Dr. Paul Genung, a "mercury-free" Seattle dentist, told the health board. "It's an outrage!"

On the other side are many large health organizations, such as the World Health Organization, the U.S. Public Health Service and the American Dental Association, which have concluded there is no scientifically compelling reason to limit or stop use of amalgam.

Dr. Victor Barry, a past president of the Washington State Dental Association, says dentists are ethically obligated to provide treatment based on "sound science" not on "junk science" that preys on patients' fears.

It can be hard for nonscientists to tell the difference.

The UW's Martin, in a presentation to the health board, tried to draw the distinction between high-end studies and those that don't prove anything. The "gold standard" is a review of randomized, double-blind studies; at the other end of the spectrum are "studies" that are essentially published anecdotes. That's the "he had herpes, and he spread peanut butter on it and got better" type of report.

When it comes to the mercury-amalgam issue, most studies haven't even had a glint of gold. Often, they've been too small, not well-designed or used questionable measuring techniques.

Some studied health effects in people with mercury levels much higher than the general population; others failed to control for other exposures to mercury.

Here and there, a solid study "proved" something, but inevitably, another "proved" just the opposite.

For example: the claim that mercury causes Alzheimer's disease. One study showed trace elements of mercury in Alzheimer's patients' brains. Another, studying a group of nuns, found those with amalgam fillings were just as sharp as those without.

Or the question of general health. One large study found Swedish women with amalgam fillings were healthier than those without (researchers suspected better attention to health matters). Another study, comparing dentists who work with mercury to nondentists, found subtle cognitive and physical impairments.

While provocative, these studies have created more confusion than clarity. But they've prompted new large-scale research, most geared to look at subtle neurological and health effects. Notably:

At Columbia University, Pam Factor-Litvak, an epidemiologist, has finished, but not yet published, a study of 550 healthy employed adults ages 30-49, examining whether low levels of mercury from amalgam fillings were associated with subtle neurophysiological deficits. The study found no evidence of such an association.

Martin and Tim DeRouen, associate dean for research at the UW's School of Dentistry, are halfway through a seven-year study of 507 schoolchildren in Lisbon, Portugal, intended to produce some definitive answers as to the safety and health effects of mercury amalgam fillings. A similar five-year study is under way in Boston.

At this point, 'the jury's out," Martin says. "I don't have a side in this issue. I just want to know what the truth is."

So do consumers and public-health officials, who worry that without amalgam, which is cheap and easy to use, children and adults will go without needed dental care. For now, the choice about fillings is a matter of weighing risks and benefits something most people do every day. For example: it may be safer to drive a big car, but what if driving a more squishable econobox means enough money left over to join a health club? (See accompanying story on principles for evaluating risk, beginning on page E 1)

What eventually happens to amalgam may have less to do with science than with lawsuits.

In recent years, they've proliferated: In Georgia, for example, the families of nine autistic children sued four drug makers, two dental industry groups and the Georgia Power Co., claiming that mercury exposure from dental fillings, vaccine preservatives and power plants caused or worsened their children's disability.

Other anti-amalgam suits have been filed against dental associations in Maryland and California.

Earlier this month, the American Dental Association sued back, charging that a Los Angeles attorney involved in the California case ran a "campaign of lies and distortion" to promote himself and his law firm.

Still, momentum seems to be building. Earlier this year, U.S. Rep. Diane Watson from Los Angeles introduced a bill requiring warning labels and banning the fillings by 2006. As a state senator in California, she sponsored a law requiring the state dental board to warn consumers of risks of amalgam, and when the dental board refused to comply, elected officials disbanded it.

Amalgam's future is very much in doubt, predicts King County Councilman Kent Pullen, who organized the recent health-board hearing. "There will be a change for economic reasons or because of consumer demand," he said. "That will come."

Copyright © 2002 The Seattle Times Company