WASHINGTON — A chemical widely used to make soap "antiseptic" survives sewage treatment and is being spread onto farmland and released into water, with unknown effects, researchers reported Tuesday.

They said the compound, called triclocarban, is not broken down by conventional sewage treatment. Researchers estimated that more than 70 percent of the triclocarban used by consumers is released to the environment when treated sludge is put on land used, in part, for food production.

There it has the potential to accumulate in crops, but researchers stressed that they have not found this.

"There are two potential threats from this chemical. One is the chemical threat and the other is the microbiological threat," said Rolf Halden of Johns Hopkins University in Baltimore, who led the study.

"When it degrades, it forms an animal carcinogen," Halden said in a telephone interview.

When any antimicrobial is widely used or released, organisms have the potential to evolve resistance to its effects, Halden said.

Writing in the June issue of Environmental Science & Technology, Halden said his studies suggest triclocarban, or TCC, contaminates 60 percent of the U.S. water supply.

"There is very little data out on the the role of triclocarbon," he said. "The irony is that we have used it for a half century and we are only beginning to learn what happens to this chemical after we are done with it."

TCC and a related compound, triclosan, are widely used in soaps and detergents.

"Ironically, the FDA determined that there is no measurable benefit to the average consumer from using these products. Everyone agrees that washing your hands is good, but there is little difference between using soap and using antimicrobial soap," Halden said.

A Food and Drug Administration advisory panel made that determination in October. The FDA has been sorting through the issue since 1972.

Halden said it was not certain that having TCC in water and sewage sludge was harmful.

"But it tells us how shortsighted we are in producing these chemicals, first without demonstrated need, and we have to ask why we are releasing these chemicals at high volume if they do no good and only cause problems down the road."

Halden said his team found in 2004 that TCC contaminated all the streams in the greater Baltimore area.

Triclosan and TCC are biocides, and break up bacteria and viruses. In 1998, Dr. Stuart Levy of Tufts University in Boston found that E. coli bacteria can develop resistance to triclosan.

Source: Reuters