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Ground-level Ozone Pollution

2015 National Ambient Air Quality Standards (NAAQS) for Ozone

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Rule Summary

In 2015, based on EPA’s review of the air quality criteria for ozone (O3) and related photochemical oxidants and for O3, EPA revised the levels of both standards. EPA revised the primary and secondary ozone standard levels to 0.070 parts per million (ppm), and retained their indicators (O3), forms (fourth-highest daily maximum, averaged across three consecutive years) and averaging times (eight hours).

EPA made corresponding revisions in:

  • data handling conventions for O3
  • changes to the Air Quality Index (AQI)
  • regulations for the prevention of significant deterioration (PSD) program
  • establishing exceptional events schedules
  • providing implementation information for the new standards

Rule History

Additional Resources

Related Rules