NEW YORK — 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 (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 (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. 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 in 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, 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.

In 1998, Swedish scientists reported that levels of PBDE in breast milk had increased 40-fold since 1972. Since the Swedish discovery, the chemical has been found in Swedish pike, Virginia catfish, and North Sea cod. Seals, moose, and reindeer all carry PBDE in their body fat and like humans, transmit it to their nursing young. PBDE has even been found in the blubber of sperm whales in the Arctic Ocean, far from any possible source of the chemical.

Even more alarming to environmentalists was the revelation in December by the journal Environmental Science & Technology that North American mothers have breast-milk PBDE levels at least 40 times the highest concentrations found in Sweden.

"What we have seen in our developmental neurotoxicity studies ... is that PBDEs can be as toxic as the PCBs," said Per Eriksson, a toxicologist at Uppsala University in Sweden. Eriksson's experiments have shown that one large dose of PBDE delivered early in a mouse's life can cause permanent brain damage.

Similar experiments by Per Ola Darnerud of Sweden's National Food Administration have determined that in mice, the smallest dose of PBDE that can cause observable health effects is about 1 million times greater than current human exposures.

But those experiments both involve relatively large amounts of PBDE given to animals over a short time. Nobody really knows how lower doses delivered over decades will affect humans. "I'm hoping that within two to three years we'll have an answer," said Kevin Crofton, a toxicologist with EPA's National Health and Environmental Effects Research Laboratory.

Faced with similar uncertainty in May 2000, the 3M Co. chose to remove another POP, known as PFOS, from Scotchgard and several other products. Like PBDE, PFOS had been found to persist in the environment, but little is known about its toxic effects.

Users of PBDE could do the same, substituting another flame-retardant chemical in its place. But PBDE has properties other flame retardants don't, Campbell said. It does not discolor foam or decrease its durability as much as other flame retardants do. And though all flame retardants evaporate into room air in trace amounts, PBDE does so at lower levels compared to many alternatives. For that reason, Great Lakes Chemical has chosen to continue producing its PBDE products for the time being.

"If things turn out that the levels that are going to get into the environment are problematic, we'll do the right thing," Campbell said.

In Europe environmental authorities have already decided that PBDE warrants action. Beginning next year, the PBDE variety that has shown up in breast milk will be banned. The European Parliament may end up banning the other types as well, because some research suggests that they can break down into the more pervasive variety after being released into the environment.

European environmental law relies heavily on the precautionary principle, which dictates that any time a human activity may pose a threat to the environment, it should be banned until it can be proven safe. In the United States, regulators must show harm or an unreasonable risk before a ban.

It likely will take a few years for scientists to figure out how much of a threat PBDE poses to human health. Then the chemical industry and government can decide if PBDE should remain in our sofas and car seats.

No matter what they decide, we will continue living many years with a stubbornly durable pollutant that has an inevitable attraction to the human body.