The chemicals were added to textiles, couches, carpet pads, mattresses, and the hard plastics in TVs, computers, and other electronic devices.

Known as PBDEs, these organic compounds are now widespread in humans and the environment. They have been detected in breast milk and human blood, including umbilical-cord blood and livers of fetuses.

Health studies suggest that they may, at high levels of exposure, cause cancer.

Within the last year, studies have also found undescended testicles in babies whose mothers had high levels of PBDEs, decreased sperm quality in men, and effects on thyroid function.

The data are "young" and not definitive, said Linda Birnbaum, a senior Environmental Protection Agency toxicologist, who has studied the chemicals for several years. "But it is concerning."

PBDEs have been found in wildlife around the planet - from seals in the Arctic to eels in the Delaware River and bluefish caught off the coast of New Jersey.

Canada, Europe, and about a dozen states - but not Pennsylvania or New Jersey - have taken action to limit or ban the most common variations of the chemicals.

Ikea began phasing out the chemicals in 1998 and since 2002 has sold no furniture containing them.

In response to bans elsewhere, in 2004 U.S. manufacturers voluntarily ceased production of the version most often used in home furniture.

But researchers worry that older furniture or carpeting is still in use and may even be in some stores.

These products "have long lives in our homes," said Heather Stapleton, a Duke University environmental chemistry professor and PBDE expert.

Worse, consumers can't tell what kind of flame retardant the products they are buying contain. "No one is required to list" them, Stapleton said.

The Centers for Disease Control and Prevention has begun monitoring levels in humans as part of its National Health and Nutrition Examination Survey.

An EPA panel's latest status report, in March, showed it was continuing to assess risks and evaluate substitutes. It also is requiring manufacturers "to develop test data that will provide a better understanding of its fate in the environment," a spokeswoman said.

But the agency drew harsh criticism this year for dismissing Deborah Rice, the toxicologist who chaired the panel. An industry lobbyist had complained that she was biased. Critics called it another case of the agency caving in to business. The Inspector General's Office is investigating.

Industry spokesman John Kyte defended the chemicals as "very efficient, very effective flame retardants." He said well-financed activists with Internet savvy had unfairly "targeted" PBDEs - or polybrominated diphenyl ethers.

What complicates matters is that PBDEs, which are one group of brominated flame retardants, have 209 possible versions.

Concern has focused on two commercial variations, penta and deca, Latin words reflecting their atomic structures.

Penta was the type used in furniture, mainly in polyurethane foam common in mattresses, carpet pads and upholstery. In 2004, it was banned in Europe, and the sole U.S. manufacturer voluntarily withdrew it from the market. Ten states have also banned it.