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Nitrogen Dioxide (NO2) Pollution

Table of Historical Nitrogen Dioxide National Ambient Air Quality Standards (NAAQS)

History of the National Ambient Air Quality Standards for NO2
Final Rule/Decision Primary/ Secondary Indicator (1) Averaging Time Level (2) Form

1971

36 FR 8186
Apr 30, 1971

Primary and Secondary NO2 Annual 53 ppb(3) Annual arithmetic average

1985

50 FR 25532
Jun 19, 1985

Primary and secondary NO2 standards retained, without revision.

1996

61 FR 52852
Oct 8, 1996

Primary and secondary NO2 standards retained, without revision.

2010

75 FR 6474
Feb 9, 2010

Primary

NO2

1 hour

100 ppb

98th percentile, 1-hour daily maximum, averaged over 3 years (4)

Primary annual NO2 standard retained, without revision.

2012

77 FR 20218
April 3, 2012

Secondary

Existing secondary NO2 standard (annual) retained, without revision.

(1)NO2 = nitrogen dioxide

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

(3)The official level of the annual NO2 standard is 0.053 ppm, equal to 53 ppb, which is shown here for the purpose of clearer comparison to the 1-hour standard.

(4)The form of the 1-hour standard is the 3-year average of the 98th percentile of the yearly distribution of 1-hour daily maximum NO2 concentrations.

Learn more about setting and reviewing standards to control NO2 pollution.