A chemical flame retardant commonly used in foam furniture padding is accumulating so rapidly in the breast milk of nursing mothers that environmentalists and some scientists are calling for a ban on it.

Little is known about the toxic nature of polybrominated diphenyl ether, commonly known by the acronym PBDE. Early studies show it poses some of the same dangers as PCBs and DDT. Those two chemicals were banned in the United States decades ago for their myriad detrimental effects on animal and human health.

Environmentalists advocate a ban on PBDE as well. One form of the chemical will be banned next year in Europe, where the law requires proof of safety before a new agent can be used in the environment. U.S. law requires proof of harm or risk before a chemical is banned.

But the chemical industry argues that more research is needed before banning something that protects lives. Producers of PBDE say there is no evidence that it will ever reach harmful levels, while its benefits as a flame retardant are well-known.

Adding PBDE to foam furniture padding, television casings and other plastics reduces by 45 percent the risk of death and injury due to fire, the chemical manufacturers say.

"We're not talking about aesthetics. People use brominated flame retardants because they save lives," said Robert Campbell, a spokesman for Great Lakes Chemical Corp. in West Lafayette, Ind.

Like PCBs and DDT, PBDE is a persistent organic pollutant, or POP. POPs can remain in the environment for years without breaking down. Some of these pollutants have such an affinity for fat that they build up in the bodies of both animals and humans from before birth until death.

"It seems that PBDEs are an important - but generally unrecognized - persistent organic pollutant in the United States," Robert C. Hale, a professor at the Virginia Institute of Marine Sciences, and five colleagues wrote in the journal Nature a few months ago.

Persistent organic pollutants are so difficult to purge from the environment that 25 years after being banned, trace amounts of PCBs can still be measured in human blood. Waterways such as New York's Hudson River and Wisconsin's Fox River are being dredged at costs running into the hundreds of millions to rid them of PCB contamination. In many waters, anglers are warned not to eat the fish they catch or to limit their consumption to one or two servings a month.

"There is an enormous need to act quickly when there is a problem with a chemical that is not only toxic but is persistent and accumulates, because it will continue to get worse before it gets better," said physician Gina Solomon, a senior scientist at the Natural Resources Defense Council.

Industry uses several forms of PBDE to decrease the flammability of various plastics. Only one of those types - used mostly in polyurethane foam furniture padding - has been found in the environment and breast milk. According to Environmental Protection Agency records, Great Lakes Chemical is the only U.S. manufacturer of that form of PBDE.

"At this point all bets are open in terms of how it's getting into the environment," said Hale, who stops short of calling for a ban on the pollutant, which was developed in the 1960s.

He has hypothesized that discarded furniture is a major source of PBDE in the environment. Whenever anybody tosses out an old sofa, he explained, nature goes to work. Water and sunlight break the foam into crumbling pieces that eventually are ground to dust. Insects have also been observed munching away at the material. From those humble beginnings the chemical travels all the way up the food chain to humans.

Hale has found PBDEs virtually everywhere he has looked: In a small river along the North Carolina-Virginia border, he found fish with the highest levels of PBDE ever recorded in an animal. He has also collected sewage sludge samples from four states, all with high concentrations of PBDE.

Swedish scientists first documented the increase of PBDE in humans. For 30 years, Sweden has sampled the breast milk of nursing mothers to track exposure to dioxin, PCBs and other pollutants that accumulate in body fat. The United States has no similar program.