The chemical had seeped into the water supply of at least six public water systems in West Virginia and Ohio. That year, Bilott filed a class action lawsuit against DuPont, Leach, et al. v E.I. du Pont de Nemours and Co., on behalf of about 80,000 people in the six water districts. He also reported his findings to the US Environmental Protection Agency and sent along copies of some 900 pages of DuPont's internal documents, after which the agency launched a "priority review" of C8. In 2004 the US EPA, too, filed a lawsuit against DuPont, charging it with concealing evidence about C8's risks for more than two decades. In 2005 the company agreed to pay $16.5 million as part of a settlement agreement with the EPA – the largest civil penalty ever in the agency's history. But environmental groups argue that the fine was little more than a slap on the wrist to a company where a single division sold more than that amount in a single day.