After a detailed study of the most widespread industrial contaminant in U.S. drinking water, the National Research Council will report today that evidence is growing stronger that the chemical causes cancer and other human health problems.
The 379-page report clears a path for federal regulators to formally raise the risk assessment of trichloroethylene, known as TCE, a step that has been tied up by infighting between scientists at the Environmental Protection Agency and the Defense Department.
California has some of the nation's worst TCE contamination, including vast tracts of groundwater in the San Gabriel and San Fernando valleys that are a drinking source for more than 1 million Southern Californians. The state's 67 Superfund sites with TCE contamination are clustered in Los Angeles and Santa Clara counties.
If the risk posed by TCE is significantly higher than previously thought, it could prompt lower limits for TCE in water, as well as stricter cleanups of hundreds of military bases and other polluted facilities. The contamination occurred because TCE, a chemical solvent, was widely dumped into the ground.
Already, some EPA offices are forcing tougher cleanups based on evidence that the chemical poses a greater-than-expected cancer risk.
The EPA attempted to issue a risk assessment in 2001 that found TCE to be two to 40 times more carcinogenic than previously thought, but that action was opposed by the Defense Department, the Energy Department and NASA. The Pentagon has 1,400 properties contaminated with TCE.
The Bush administration sent the matter to the National Research Council for study, based on military assertions that the EPA had overblown the risks. But the new report does not support that criticism.
"The committee found that the evidence on carcinogenic risk and other health hazards from exposure to trichloroethylene has strengthened since 2001," the report said.
The report urged federal agencies to complete their assessment of TCE risks as soon as possible "with currently available data," meaning they should not wait for additional basic research, as suggested by the Defense Department.
The report is to be formally released today by the National Research Council. An early copy was provided to The Times by the Natural Resources News Service, a Washington, D.C., nonprofit that investigates environmental issues. The authors of the study also briefed members of Congress on Wednesday.
