Heavy Metal Risks

Feds to Dentists: Get the Lead Out Lead-lined film safes present heavy metal exposure risk

By Adam Marcus HealthScoutNews Reporter

THURSDAY, Oct. 11 (HealthScoutNews) -- Dentists who still store X-ray film in lead-lined boxes are putting patients at risk of exposure to the harmful heavy metal and should stop the practice immediately, say health officials.

Powder shed from the lead can get onto the hands of office workers who handle X-rays, or it can even coat the film itself. In both cases the lead may wind up in a patient's mouth, officials say. The risk is particularly a concern for children and pregnant women, because lead harms developing brain cells.

As a result, officials say, doctors with young patients who have mysteriously high blood levels of lead should consider dental exposure as a possible culprit.

"It's a completely unnecessary potential risk. Even if it's a tiny amount of lead that gets [into a patient's bloodstream], it's too much," says Marc Weisskopf, a researcher at the Harvard School of Public Health who led a study on the matter while he was with the Centers for Disease Control and Prevention in Wisconsin. "Many times we have to balance risk and benefit, and here there's no benefit, so there's no balance to be done."

However, Weisskopf adds, there is also no evidence that people have suffered lead poisoning after a trip to the dentist. A report on the study was released today by the CDC.

The inkling of a problem was first reported to Washington State health officials in June 2000 by a dental hygienist in Olympia, says Mike Odlaug, X-ray manager for the Washington Department of Health. The woman had noticed a white, powdery buildup on X-ray film stored in shoe-box-sized lead-lined boxes at the two offices where she worked. Lab tests of the powder revealed it to be lead oxide.

Washington officials alerted the CDC, the American Dental Association and the Food and Drug Administration, which issued a letter to dentists about the problem in March of this year. According to that alert, "In many cases there are highly dangerous levels of lead on the films, enough to potentially cause serious adverse health effects in patients and health care professionals. These adverse health effects include anemia and serious neurological damage."

In the Wisconsin inquiry, inspectors surveyed 240, or 9 percent, of the state's 2,800 dental offices between January and March of this year. One in six kept X-ray film in lead-lined, table-top boxes, all of which were found to contain a white powdery residue. Tests of the powder showed it to be almost 80 percent lead oxide.

In a mock X-ray procedure with film kept in a lead-lined box, state investigators found that wipes used to clean a hygienist's fingers whenever they touched a patient's mouth collected almost 3,400 micrograms of lead dust. Wipe samples of film packets stored in lead-lined boxes at two dental offices were tested and found to have average levels of the metal at 3,351 micrograms, and a peak of 34,000 micrograms.

The CDC considers a blood lead level of 10 micrograms per deciliter to be the upper limit for children, but that is usually applied to chronic exposure to the toxin, the kind that results from living amid lead paint dust. A one-time exposure of 3,400 micrograms, provided all that lead managed to enter the bloodstream, would be enough to temporarily drive a child's blood lead level well above 10, Weisskopf says.

What the health implications of that spike would be are is unclear, he says, though mounting evidence suggests that even lead levels below 10 micrograms per deciliter would be of concern. "We really can't consider any amount safe, and since this is completely avoidable, there's absolutely no sense in keeping these boxes around."

Lead-lined boxes were common decades ago when X-ray machines delivered doses large enough that the scattered radiation fogged unshielded film. Not surprisingly, in the Wisconsin study, the odds of having a lead-lined box doubled for offices that had been open for more than 20 years.

But modern equipment has eliminated the problem of scatter, Odlaug says, and X-ray film can be kept safely in a desk drawer or steel-lined container. Lead boxes can be dust-proofed by coating them with epoxy or paint, he says.

Although dentists nationwide should now be familiar with the problem associated with lead-lined boxes, it's far from certain they've taken steps to rid their offices of the hazard, Weisskopf says.

While the Wisconsin inquiry was underway, the state sent letters notifying dentists of the exposure issue. Yet when the investigators arrived, "many had tossed it in the trash or thought it was junk mail. There were plenty that were still using these boxes," he says.

The American Dental Association did not return calls for comment.

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