The Sierra Club asked the Environmental Protection Agency on Tuesday to ban industrial and household detergents containing nonylphenol ethoxylates, or NPEs, a class of toxic chemical compounds that can cause male fish to develop certain female characteristics.

The petition, which is also signed by the Pacific Coast Federation of Fisherman's Associations and the textile-and-hotel-workers union UNITE HERE, also seeks to require labeling on all products containing NPEs and to bar their use in areas where wastewater treatment plants aren't equipped to remove them.

If the effort succeeds, it would be the first U.S. restriction on a substance principally because it is an endocrine disruptor, said Ed Hopkins, director of the Sierra Club's environmental quality program. Endocrine disruptors mimic or antagonize natural hormones and are thought to be responsible for some reproductive problems in both women and men, and for increases in the frequency of certain cancers, according to an EPA fact sheet.

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Scientists have documented in the last decade so-called intersex fish in U.S. waters, including the southern Great Lakes, the Potomac River watershed and the Southern California coast. The reasons for the problem aren't fully known, but researchers suspect it is rooted in wastewater and farm runoff polluted with chemicals that are estrogenic, meaning they stimulate estrogen production.

NPEs are more tightly restricted in Canada and Europe than in the United States, which issued water-quality limits for the key ingredient, nonylphenol, or NP, in December 2005. Detergent manufacturers Procter & Gamble and Unilever have voluntarily substituted other chemicals in their products, and Wal-Mart is seeking to phase NPEs out of its stores by rewarding companies that find alternatives.

"We think it's time for the U.S. Environmental Protection Agency to take action and restrict this chemical," Hopkins said.

The Alkylphenols & Ethoxylates Research Council, a Washington-based trade group for major producers of nonylphenol and NPEs, said the compounds have been thoroughly reviewed.

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"NP, NPE and their biodegradation intermediates are among the most extensively studied compounds in commerce today," Robert Fensterheim, the trade group's executive director, said in an e-mailed response to questions from The Associated Press. "Few compounds have the same degree of test data and have received the same degree of scrutiny."t But Hopkins said the EPA didn't consider NPEs' endocrine-disrupting effects in setting water-quality limits because the 1985 guidelines for setting toxicity criteria don't recognize endocrine-disruptor research.

"They set criteria based on conventional toxicity tests," Hopkins said. "But those criteria don't take into account the fact that NP and NPEs affect fish more subtly at far lower levels."

The petition states that the known effects of NP and NPEs on aquatic life include elevated levels of an egg-yolk ingredient in male rainbow, trout, flounder, Atlantic salmon and eelpouts, a family of eel-like fish; reduced salmon abundance; estrogenic effects in amphibians, and toxicity to marine oysters.

The petition seeks more study of NPEs, including testing for health effects on industrial laundry workers.

The EPA is developing a program, the Safer Detergents Stewardship Initiative, that would recognize companies that voluntarily commit to use safer substitutes for NPEs.

Wastewater treatment plants remove 90 percent to 95 percent of primary compounds, according to an industry study cited in the petition. But the petition states that even if all of the approximately 400 million pounds of NP and NPEs produced each year received 95 percent treatment, more than 10 million pounds of the chemicals would be released into the environment each year.

The petition also is signed by the Environmental Law & Policy Center, the Washington Toxics Coalition and Physicians for Social Responsibility.