2008 8-Hour Standards

On March 12, 2008, EPA issued a revised primary and secondary National Ambient Air Quality Standard (NAAQS) for ozone. The revised more-stringent primary standard for ozone was set at 0.075 parts per million (ppm) measured over an 8-hour period. EPA also revised the secondary standard, designed to protect welfare, at 0.075 ppm, making it identical to the primary standard. The existing ozone standard was set in 1997 at 0.08ppm.

EPA is expected to finalize the nonattainment designations by March 2010 based on these revised standards. According to this schedule, conformity will apply in 2011, one year after the final nonattainment designations become effective.

Further information regarding the revised NAAQS is available on EPA's website