The U.S. Environmental Protection Agency (EPA) has enough data to complete its risk assessment of trichloroethylene (TCE), a likely carcinogen and widespread contaminant of groundwater, soil, and air across the United States. That's the conclusion of a panel convened by the National Academies' National Research Council (NRC), which released a report on the subject today.
TCE has been the focus of a lengthy, high-stakes battle between EPA and other federal agencies that are responsible for the expensive cleanup of TCE. The solvent was widely used for decades as an industrial degreasing agent and often dumped in local landfills; it's still in use, although in smaller quantities. TCE can enter homes through contaminated drinking water, or as vapors from soil, and hundreds of military, industrial, and waste sites have been contaminated.
A 2001 draft risk assessment raised EPA's estimate of the compound's potency as a carcinogen by 2 to 40-fold, which triggered criticism from the Department of Defense and other agencies. Despite an overall positive review by EPA's science advisory board, which called for the agency to "finalize the draft assessment as quickly as it can," NRC was asked in 2003 to evaluate the state of the science.
The panel, chaired by toxicologist Rogene Henderson of the Lovelace Respiratory Research Institute in Albuquerque, New Mexico, pointed to new epidemiological studies confirming that TCE can cause kidney cancer and may lead to other kidney problems, although the dose that triggers these problems isn't known. Animal studies suggest that high doses can cause liver cancer and infertility, but it's not clear whether these studies are relevant to humans. Inhalation of TCE seems to cause neurological problems, such as poor coordination in both humans and lab animals, and appears to aggravate autoimmune problems.
Although more research is needed to determine how TCE causes these adverse health effects, the panel concluded, there are enough data for EPA to finish its risk assessment. EPA needs to spell out more clearly the bases for its risk assessment, the panel said. But Henderson says the assessment should be completed in 6 months to a year. "It's time they finish their risk assessment," she says.
"It's a clear call to action," says Gina Solomon of the Natural Resources Defense Council, a member of the EPA advisory board panel that examined TCE. "The science has only become stronger with time." EPA will follow the risk assessment with revised standards for clean up and drinking water.
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