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Ozone Pollution

Table of Historical Ozone National Ambient Air Quality Standards (NAAQS)

History of the NAAQS for Ozone, from 1971 to 2015
Final Rule/Decision Primary/Secondary Indicator1 Averaging Time Level2 Form
1971

36 FR 8186 
Apr 30, 1971
Primary and Secondary Total photochemical oxidants 1 hour 0.08 ppm Not to be exceeded more than one hour per year
1979

44 FR 8202 
Feb 8, 1979
Primary and Secondary O3 1 hour 0.12 ppm Attainment is defined when the expected number of days per calendar year, with maximum hourly average concentration greater than 0.12 ppm, is equal to or less than 1
1993

58 FR 13008 
Mar 9, 1993
EPA decided that revisions to the standards were not warranted at the time
1997

62 FR 38856 
Jul 18, 1997
Primary and Secondary O3 8 hours 0.08 ppm Annual fourth-highest daily maximum 8-hr concentration, averaged over 3 years
2008

73 FR 16483 
Mar 27, 2008

Primary and Secondary

O3 8 hours 0.075 ppm Annual fourth-highest daily maximum 8-hr concentration, averaged over 3 years

2015

80 FR 65292
Oct 26, 2015

Primary and Secondary O3 8 hours 0.070 ppm Annual fourth-highest daily maximum 8 hour average concentration, averaged over 3 years

1. O3 = ozone

2. Units of measure are in parts per million (ppm)