Ozone Trends
Under the Clean Air Act, the EPA sets national ambient air quality standards (NAAQS) for ozone 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 ozone concentrations to ensure that the NAAQS are being met. The charts below based on this measurement data show that nationally, ozone concentrations have decreased over the years. For information on ozone standards, sources, health effects, and programs to reduce ozone pollution, please see our Ground-level Ozone Pollution page.
EPA uses a statistical model to account for the weather-related variability of seasonal ozone concentrations to provide a more accurate assessment of the underlying trend in the precursor emissions that cause ozone. See Trends in Ozone Adjusted for Weather Conditions.
