Showdown Over Clean Air Science

<p> On 16 July, the U.S. Environmental Protection Agency unveiled final air pollution rules designed to tighten ozone standards and clamp down on particles. The cost of implementing the rules has sparked a fierce protest on Capitol Hill from industry groups and many state and local officials. Industry and environmental researchers are also squaring off over the science behind the rules on fine particles in what some are calling the biggest environmental fight of the decade. </p>