DENVER Nearly two dozen states and several cities on Wednesday filed a legal challenge to the Trump administrations rollback of Obama-era mileage standards, saying science backed up the old regulations developed with the help of the nation's car makers. The new mileage standards require automakers to achieve 1.5% annual increases in fuel efficiency. The Obama-era standards called for 5% annual increases and were seen as the government's most forceful initiative against climate-changing fossil fuel emissions. The states and cities claim the rule violates the Clean Air Act, the Energy Policy and Conservation Act and the Administrative Procedure Act. Opponents claim dirtier air from the rollback will kill and injure more people than the rollback claims to save in roadway accidents.