Nitrogen Dioxide (NO2)

On January 22, 2010, the EPA issued a new primary National Ambient Air Quality Standard (NAAQS) for nitrogen dioxide or NO2. The new standard is based on a criterion for the highest one-hour average per sampling day. Monitors are likely to be deemed not attaining this standard if the 98th percentiles of such daily maximums averaged over three consecutive years exceed 100 parts per billion (ppb). Previously, both the primary and secondary NAAQS were attained if the annual arithmetic mean concentration was not greater than 53 ppb. This criterion is still used as a secondary NAAQS.

NO2 'Design Value' Maps

To aid in planning for attainment of the 1-hour NO2 standard, the following North Carolina maps have been drawn showing the 3-year-average 98th percentile of maximum 1-hour concentrations in each county. Click on links for printer-friendly version. North Carolina counties with 1-hour NO2 monitors: