Some…oil companies…have agreed to pay about $423 million in cash to settle a lawsuit brought by more than a hundred public water providers, claiming water contamination from a popular gasoline additive…[T]he companies also agreed to pay 70 percent of the future cleanup costs over the next 30 years. The defendants that agreed to the settlement included BP, Royal Dutch Shell, ConocoPhillips, Chevron, Marathon Oil, Valero Energy, Citgo and Sunoco. Six other companies named in the lawsuit, including Exxon Mobil, did not agree to the deal…The suit contended that the chemical was used by oil companies, even though they knew of the environmental and health risks that it posed…[A] lawyer representing Exxon…said…[the company] would "vigorously defend" itself.