Summary:

Based on its review of the air quality criteria for ozone (O3) and related photochemical oxidants and national ambient air quality standards (NAAQS) for O3, EPA is making revisions to the primary and secondary NAAQS for O3 to provide requisite protection of public health and welfare, respectively. With regard to the primary standard for O3, EPA is revising the level of the 8-hour standard to 0.075 parts per million (ppm), expressed to three decimal places. With regard to the secondary standard for O3, EPA is revising the current 8-hour standard by making it identical to the revised primary
standard. EPA is also making conforming changes to the Air Quality Index (AQI) for O3, setting an AQI value of 100 equal to 0.075 ppm, 8-hour average, and making proportional changes to the AQI values of 50, 150 and 200.

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