A suspected carcinogen used to make nonstick and stain- and water-resistant products contaminates white Americans at three times the rate of Mexican Americans and nearly twice that of blacks, according to new data from the Centers of Disease Control and Prevention.

Men in all three groups are slightly higher than women, according to the research, slated for publication in the April 1 edition of Environmental Science and Technology.

CDC researchers cannot explain the differences, though genetic and lifestyle factors are primary culprits.

"It is difficult to know," said Antonia Calafat, senior research chemist at the CDC's National Center for Environmental Health and the paper's lead author. "Everything would be a speculation."

The contaminants, known as perfluorochemicals or PFCs, are widely found in low levels in people and wildlife across the globe. In higher doses, they are suspected of causing cancer and other health problems in laboratory animals. Last month, a U.S. Environmental ProtectionAgency panel advised regulators to classify one of them, perfluorooctanoic, or PFOA, as a likely human carcinogen.

Since the 1950s, the chemical family has become an increasingly important staple in the manufacture of a wide range of industrial and consumer products: stain-resistant carpets and textiles, packaging materials for fast food and snack items, nonstick coatings on cookware, even ant bait.

But while CDC researchers aren't drawing conclusions,

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one small study suggests lifestyle may play a role. Last year, Calafat and her CDC colleagues published a report showing Peruvian adults had much lower PFC levels than their American counterparts. Given many PFC-containing products are more prevalent in the United States, the Calafat speculated lifestyle could be the reason for the lower levels.

On Wednesday she declined to draw any similar conclusions for the ethnic differences among U.S. adults.

What the study does show, she said, was that non-Hispanic whites somehow absorb more of the contaminant. White males averaged 7 parts per billion PFOA in their blood, while white women averaged 4 ppb. A part per billion is roughly akin to splitting a chocolate bar with the city of San Francisco. Mexican Americans tested had levels one-third what CDC researchers found in whites. Blacks were about half, or 3.6 ppb for black males and 2.8 ppb for black females.

This newspaper's investigation of our chemical "body burden" tested a white Berkeley family for PFCs, among other chemicals. The father, Jeremiah Holland, had 3.6 ppb PFOA, while his wife, Michele Hammond, had 0.4 ppb. Their two children had almost 7 ppb each.

And though PFOA is a key processing aid in the manufacture of Teflon, among many products, researchers are stumped when it comes to finding a source for that pollution.

In other words, Calafat said, don't toss out the Teflon pan just yet.

Based on the peer-reviewed science, she said, "it doesn't seem these chemicals can come from Teflon. But it is also true that there are some sources of these compounds we don't know yet."

"They could come from many sources."

This newspaper's special investigation of our chemical body burden, "A Body's Burden: Our Chemical Legacy," can be found on the Web at http://www.insidebayarea.com/bodyburden.