Court Upholds Rule on Nitrogen Dioxide Emissions A three-judge federal appeals panel on Tuesday upheld the first-ever federal rule protecting people from acute exposure to emissions of nitrogen dioxide, a pollutant implicated in asthma attacks and other respiratory problems. The judges rejected a challenge from the American Petroleum Institute, ruling that both science and the law justified a 2010 decision by the Environmental Protection Agency to limit maximum one-hour concentrations of nitrogen dioxide in the atmosphere to 100 parts per billion. More than half the nitrogen dioxide in the atmosphere comes from vehicles, and concentrations are greatest along highways.