The U.S. Environmental Protection Agency (EPA) has issued a final rule setting new source performance standards (NSPS) under the Clean Air Act for nitric acid plants. 77 Fed. Reg. 48,433 (8/14/12). The new rule includes new nitrogen oxide limits for each nitric acid production unit “commencing construction, modification, or reconstruction after October 14, 2011.” The rule revises the NS PS for nitric acid plants, setting an emission limit of 0.50 pound of nitrogen oxides per ton of acid produced. Compliance must be calculated using a 30-day average. The 0.50-pound standard is down from a 3-pound-per-ton limit EPA established in 1971. The final rule took effect August 14, 2012.