Nitrogen Dioxide Trends

Under the Clean Air Act, the EPA sets national ambient air quality standards (NAAQS) for nitrogen dioxide (NO₂) at levels that are safe for public health and the environment. Air quality monitors operated by federal, state, local and tribal agencies throughout the country collect ambient measurements of NO₂ concentrations to ensure that the NAAQS are being met. The charts below based on this measurement data show that nationally, NO₂ concentrations have decreased substantially over the years. For information on NO₂ standards, sources, health effects, and programs to reduce NO₂ pollution, please see our Nitrogen Dioxide Pollution page.