Trichloroethylene

A House committee is demanding to know why federal regulators failed to assess potential public health damage from extremely high levels of a toxic industrial solvent found in Southern California drinking water before the mid-1980s. Trichloroethylene, widely used in the defense industry, was discovered in aquifers under the San Gabriel and San Fernando valleys, which supplied drinking water to nearly 2 million residents.

After massive underground plumes of an industrial solvent were discovered in the nation's water supplies, the Environmental Protection Agency mounted a major effort in the 1990s to assess how dangerous the chemical was to human health. Following four years of study, senior EPA scientists came to an alarming conclusion: The solvent, trichloroethylene, or TCE, was as much as 40 times more likely to cause cancer than the EPA had previously believed.

Residents of a south Chico neighborhood have been told to drink bottled water and avoid taking showers after county health officials determined their groundwater was contaminated. Butte County Environmental Health officials tested 40 wells in the area, finding traces of TCE, a solvent used in industry, in 25 of them. In nine of the wells, the TCE level exceeded state and federal safety standards.