For decades, Shell and Dow hid a highly potent cancer-causing chemical in two widely used pesticides, contaminating drinking water for millions of people in California and beyond, according to lawsuits detailed in a new report from the Environmental Working Group (EWG). The chemical 1,2,3-trichloropropane or TCP, was formerly an unwanted and ineffective byproduct in Dow's Telone and Shell's D-D pesticides. Internal documents uncovered in lawsuits filed by communities in California's San Joaquin Valley show that the companies saved millions of dollars a year by not properly disposing of TCP, a chemical a Dow scientist once called "garbage," as hazardous waste. Shell stopped making D-D in 1984 and Dow later took TCP out of Telone, but not before it contaminated the tap water supplies of 94 California utility districts serving 8 million people. An U.S. Environmental Protection Agency testing program found TCP in tap water