Nitrogen Dioxide Trends
Air quality monitors measure concentrations of NO2 throughout the country. EPA, state, tribal and local agencies use that data to ensure that NO2 in the air is at levels that protect public health and the environment. Nationally, average NO2 concentrations have decreased substantially over the years. The charts below show national and regional trends in NO2 concentrations. For information on NO2 standards, sources, health effects, and programs to reduce NO2, please see our Nitrogen Dioxide Pollution page.