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CDC study finds dramatic drop in levels of lead in American bodies

WASHINGTON—Americans have dramatically cut the levels of lead and secondhand tobacco smoke in their blood and urine, a new federal study found Thursday. But new toxins are showing up, and the levels of cadmium—a nasty heavy metal—are worrisome.

The Centers for Disease Control and Prevention said its latest and most comprehensive study of chemicals in American bodies showed that efforts to reduce smoking and remove lead from gasoline had worked to improve health. At the same time, the new chemicals—including those prevalent in plastics and pesticides—are drawing concern and focusing research on what levels of these chemicals in humans are dangerous.

"We shouldn't be too scared but we can't be complacent, because there's a lot we don't understand," said Thomas Burke, a Johns Hopkins University environmental health professor who heads a National Academy of Sciences board on biomonitoring.

CDC Director Julie Gerberding said the results of the examination of 148 chemicals in American bodies were "great news," showing that "over the last decade there has been an astonishing reduction in exposure to tobacco smoke in the environment."

But it wasn't all good news.

"Some things we're finding going down; some things are raising eyebrows, and we're going to pay more attention to them," said Jim Pirkle, the deputy director for science and environmental health at the CDC.

Levels of the key chemical marker for secondhand smoke fell 75 percent for adults and about 68 percent for children compared with a decade earlier.

Only 1.6 percent of children 5 and younger had lead levels that traditionally have been considered high. That's down from 4.4 percent in the early 1990s. Before lead was taken out of gasoline starting in 1973, well more than half of American children had elevated lead levels.

Recent scientific studies have found that no amount of lead in the blood is safe, officials said.

Thursday's CDC study also showed that more than 5 percent of the American public has levels of cadmium that could be dangerous. Pirkle said the new study showed that cadmium was dangerous to kidneys and could cause cancer at lower levels than previously thought. More than 1 in 20 Americans have cadmium levels higher than those new lower thresholds, he said.

The cadmium levels—which rose from the late 1990s—are surprising and troubling, said Michael Thun, the head of epidemiology for the American Cancer Society and a longtime cadmium researcher.

Cadmium levels should be decreasing, because smoking is the metal's major environmental source, Thun said. It also could come from food, which might be absorbing it through the soil from the burning of batteries, plastics and other modern substances.

Widespread use of common insecticides also showed up in American blood and urine.

More than 5 percent of American women of reproductive age have worrisome levels of three phthalates, a type of chemical commonly used in plastics and cosmetics. Initial human studies and many rat studies link high levels of these chemicals in pregnant women to boys being born with smaller genitals and deformed reproductive systems.

"We're always taking things in from the environment; for good or for bad, our bodies reflect the environment," said Burke, of Johns Hopkins.

Chemical and farm industry officials hailed the massive CDC report as showing that there isn't much to worry about from using everyday chemicals.

But Jerome Paulson, a professor of pediatrics and public health at George Washington University, said the study showed lots of chemicals in the human body and couldn't say they were at safe levels.

"I think what this report shows is the extent to which we as human beings on a worldwide basis have really fouled our nests," Paulson said. "We have placed unintentionally a lot of chemicals in our bodies that were not intended to be in our bodies."


The 475-page CDC study can be found on the CDC's Web site, at


(c) 2005, Knight Ridder/Tribune Information Services.

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