The California Department of Health Services announced Thursday that it will allow drinking water wells to contain higher concentrations of a chemical previously suspected to cause cancer in animals.
State health officials said they have concluded that the chemical, known as DCE, is not nearly as toxic to humans as earlier studies suggested.
They said they reached that conclusion after a review of scientific literature as well as a reevaluation of DCE by the U.S. Environmental Protection Agency and testing by the U.S. Public Health Service’s National Toxicology Program.
The decision means that about 30 wells in the Los Angeles region that could not meet the previously and more stringent recommended safety level of .2 parts per billion will be able to meet the new 6.0 parts per billion level.
The chemical--1, 1-dichloroethylene--is used in the formation of other chemicals and has been found in wells in the San Gabriel, Salinas and San Joaquin valleys.
Based on Italian Study
Alexander Kelter, chief of the health service’s Office of Environmental Health Hazard Assessment, said the former recommended maximum concentrations were based in large part on a 1984 Italian study involving rats that is now being discounted because it lacked “quality control” and “good lab analysis.”
The study had indicated that DCE is a possible cancer-causing agent in animals. Now, however, Kelter said DCE is being treated as a non-carcinogenic, although still toxic, agent.
Despite doubts about the Italian study’s reliability, both federal and state officials took it into account in arriving at the new recommended safety concentrations, Kelter said.
He noted that the EPA last autumn proposed a recommended maximum contaminant level of 7.0 parts per billion.
“Just because it wasn’t reviewed properly doesn’t mean it was wrong,” Kelter said of the Italian study. “You just didn’t have enough confidence that it was right.”
He added that the “extra-large safety margin” in the new action level means that, statistically, if a person were to drink two liters of water a day containing 6 parts per billion of DCE for 70 years, there would be no observable adverse health effects.
But Lawrie Mott, project scientist with Natural Resources Defense Council Inc., an environmental group, questioned whether state officials had relaxed the DCE standard on the basis of incomplete data.
Gary Yamamoto, district sanitary engineer for the state Health Services Department, said seven Los Angeles-region water companies will be affected by the new standard.
They include San Gabriel Valley Water Co., which has five DCE-contaminated wells; a well in Duarte operated by California-American Water Co.; an East Los Angeles well operated by California Water Service Co.; East Pasadena Water Co.; Southern California Water Co.'s wells in Norwalk and Claremont; the City of Pomona, and Suburban Water Systems’ wells located above the Whittier Narrows Dam.