Why did some courts conclude that compliance with the Clean Air Act does not preclude oil companies from liability?

What will be an ideal response?

Oil companies have had mixed results in cases in which they have argued that the Clean Air Act preempts their liability for methyl tertiary butyl ether (MTBE) water contamination. In an attempt to reduce air pollution in certain areas, Congress mandated that gasoline contain an oxygenate, which allows gasoline to burn more cleanly. Congress, however, did not require that a particular oxygenate be used. Most oil companies added the oxygenate MTBE to gasoline. Unfortunately, even very small amounts of MTBE can contaminate drinking water: It affects the smell and taste of water and may cause health problems. Public water utilities and private individuals, faced with millions of dollars in cleanup costs, began suing oil companies for damages to resolve the water contamination. In response, oil companies, raising the preemption defense, argue that because the government required them to add an oxygenate to gasoline, oil companies should not be responsible for the water contamination. Plaintiffs argue that oil companies chose to use MTBE; other oxygenates, such as ethanol, were available. Several courts have concluded that the Clean Air Act preempts oil companies' liability, but other courts have reached the opposite conclusion, emphasizing the fact that oil companies had a choice. Furthermore, these courts hold that the purpose of the Clean Air Act was to address air pollution, and the MTBE water contamination is a problem too far removed from the purposes of the Clean Air Act to preempt product liability claims associated with MTBE.