The Environmental Protection Agency proposed more stringent nitrogen oxides performance standards for nitric acid plants September 30 but said that it will not seek greenhouse gas emissions standards for them. The proposed rule would revise the new source performance standards by limiting nitrogen oxides to 0.5 pound per ton of acid produced, calculated as a 30-day rolling average. The Fertilizer Institute, which represents 90 percent of nitric acid plants, is concerned that the industry will be able to meet the standard.