Both were found in the study participants, even in some who hadn't been born until after the chemical compounds were removed from products here.

That's because the substances take many years to break down. PCBs, for example, were banned in the United States in 1977. But "about 70 percent of what was ever made is still out there," said Linda Birnbaum, an Environmental Protection Agency toxicologist in North Carolina.

Other chemicals the project measured aren't subject to much regulation. They include the compound used to make DuPont's popular Teflon nonstick cookware, as well as the flame retardants in many mattresses and television wires. Both types of chemicals were found in study participants.

Questions about the potential health impact have sparked an increasingly contentious debate over whether the government should do more to protect people. The outcome could have a huge impact. Evidence of harm could force companies to change how they make many common household items and open them up to multimillion-dollar lawsuits.

Some chemical manufacturers are taking precautionary measures. In the past six years, companies including DuPont and 3M have voluntarily withdrawn or have committed to phase out and replace the chemical compounds used in nonstick pans, stain-resistant carpets and flame retardants.

Industry officials, however, say the concentrations of chemicals are so low that they're harmless.

Some of the amounts found are so small that the technology to detect them did not exist until about 15 years ago.

"These are tiny levels of compounds which now suddenly we can detect," said Sarah Brozena, a senior director at the American Chemistry Council, the industry trade association. "Finding a chemical in our bodies is merely finding evidence of an exposure. It doesn't tell you anything about the source of the exposure or how big the exposure was that caused it. And it especially doesn't tell you anything about what risk it might pose at that level."

Brozena and others say having low levels of toxic chemicals in your body is part of the tradeoff for such a high standard of living.

"I tend to think we ought to be a little bit careful before we start saying, 'Oh, everything we ingest is horrible, and it's killing us,"' said Roger Meiners, an economics and law professor at the University of Texas at Arlington who says the federal government overregulates environmental pollutants. "We're living longer and longer, so overall it seems to be working pretty well."