Dec. 2 (Bloomberg) -- Male fish living near sewer pipes in Los Angeles's coastal waters are developing female sex organs, renewing concern that contaminants dumped in the ocean 30 years ago pose health risks.

The gender bending, the first time observed in ocean fish, was discovered by the Southern California Coastal Water Research Project in May. Eleven of 64 bottom-dwelling fish caught near sewage pipes from Santa Monica to Huntington Beach had ovary tissue in their testes, according to a study by the group.

DDT, a pesticide banned in the U.S. 30 years ago, may be causing the abnormalities, said Dan Schlenk, an aquatic ecotoxicologist at the University of California in Riverside and co-author of two of three papers on the Los Angeles-area fish. The studies are a reminder to local residents that consuming fish from the Santa Monica Bay may pose health risks.

``If a friend came back from fishing and offered me a fish from his boat, yeah I would eat it, but I wouldn't do it on a regular basis,'' said Matt Stein, chief seafood officer at King's Seafood Co., owner of Ocean Avenue Seafood in Santa Monica California. ``Whether it's the mercury in the water or DDT, it's all about moderation.''

Los Angeles sewers that drain into the Santa Monica Bay, which stretches from Point Dume in the north to the Palos Verdes peninsula in the south, served as a dumping ground for DDT, dichloro-diphenyl-trichloroethane, starting in the 1950s.

Pollution

In 2000, companies including Montrose Chemical Corp. of California, Aventis CropScience USA, Chris-Craft Industries Inc. and Atkemix Thirty-Seven Inc. agreed to a $73 million settlement with California and U.S. prosecutors to clean up ocean contamination around Los Angeles, the Environmental Protection Agency said on its Web site.

In a 1994 report, the U.S. Geological Survey identified elevated levels of DDT and PCBs in a 17 square-mile area around Palos Verdes, which lies about 20 miles south of downtown. Eating fish contaminated by chemicals such as DDT and PCBs, polychlorinated biphenyls, can increase cancer risk, harm the liver and affect the central nervous system, the EPA said.

The California Office of Environmental Health Hazard Assessment currently has consumption warnings for species including white croaker, corbina, sculpin, rock fish and kelp bass, primarily due to concerns about DDT and PCBs in the Los Angeles area, department spokesman Allan Hirsch said.

Estrogen

DDT mimics estrogen in its effects on some animals, possibly causing the development of female characteristics in male hornyhead turbots and English sole, according to the study by the Southern California Coastal Water Research Project. Other so- called estrogenic compounds that may cause female traits may also be found in sunscreen, Schlenk said.

``The most significant aspect of this study is that it's the first time that we have found these kind of symptoms in salt water fish,'' said Steve Weissberg, director at the Southern California Coastal Water Research Institute.

The studies, which will be followed by more research, don't address human health risks, Schlenk said. Some studies have linked hormone-mimicking chemicals to decreased sperm counts, altered genitalia in baby boys and premature puberty in girls.

``Exposure to DDTs and other persistent contaminants that show estrogenic activity can occur through dietary consumption of fish,'' Schlenk said. ``The relative risk of adverse effects depends on the dose.''

Treatment

While the government has banned dumping toxic chemicals into sewers, the practice left ocean outflow sites contaminated. Los Angeles County and city together process about 650 million gallons of waste water a day, the third-largest output in the U.S. behind Chicago and New York City.

The county's 11 treatment plants don't filter out all potentially harmful chemicals.

``There are some natural contaminants that treatment plants may not catch completely such as tannins,'' said Bob Horvath, head of Technical Services at the Los Angeles County Sanitation District. ``These studies can't look at all of them so they focus on key things, like hormones.''

The biggest source of ocean pollution in Los Angeles, which has a population 3.7 million, is rain runoff from city streets, said Hirsch of the state environment office.

Mayor Antonio Villaraigosa's plans for improving water quality include revitalizing the Los Angeles River and improving catch basins for storm water, said Nancy Sutley, deputy mayor for energy and the environment. The mayor doesn't have a specific plan for addressing DDT and pesticide pollution in the ocean, she said.

Causation

``The big picture for the few fish that are left is that they are slowly being poisoned,'' said Gordon Labedz, conservation committee chair at the local chapter of the Sierra Club. ``Whether it's from sewage plants or from runoff. Our coastal ocean is at great risk in the long run.''

Local charter-boat fishermen and their clients often keep their catch for dinner. Marina Del Rey Sportfishing hosts 20 to 40 customers a day, including customers who have returned for 15 years. Their regular catch includes rock cod, bass and halibut.

``We've been eating fish from these waters for years,'' said Rick Arnold, 36, who has worked at the company for 21 years and lives in Marina Del Rey. ``I am 6'5 and 300 pounds. I eat our fish three times a week. I don't think there's anything wrong with me.''

To contact the reporter on this story: Nadja Brandt in Los Angeles at nbrandt@bloomberg.net.

Last Updated: December 2, 2005 03:00 EST