EPA last week revised a 2009 Clean Air Act regulation that limits emissions of hazardous air pollutants from hundreds of chemical manufacturing facilities. The agency made several highly technical alterations sought by the chemical industry to facilitate compliance with the complex rule. Two trade associations, the American Chemistry Council and the Society of Chemical Manufacturers & Affiliates (SOCMA), petitioned EPA to make the changes. The groups argued the regulation had many flaws and asked the agency to address them. William E. Allmond IV, SOCMA’s vice president of government and public relations, says EPA’s changes to the 2009 rule “address several, but not all, of our top concerns” about the regulation. The rule applies to some 450 U.S. chemical manufacturing facilities that release less than 10 tons per year of any one of the scores of air pollutants listed as hazardous in the Clean Air Act or less than 25 tons per year of any combination of these air toxics.