EPA Proposes to Retain Current NO2 NAAQS

July 14, 2017 – Based on its review of the current body of scientific evidence, EPA is proposing to retain the current primary National Ambient Air Quality Standards (NAAQS) for oxides of nitrogen without revision.  The proposal is consistent with the recommendation of the Clean Air Scientific Advisory Committee, EPA’s independent scientific advisors, which provided its advice to the EPA Administrator earlier this year.  There are currently two nitrogen dioxide (NO2) standards: 1) a 1-hour standard, established in 2010, at a level of 100 parts per billion (ppb) and based on the 98th percentile of the annual distribution of daily maximum 1-hour NO2 concentrations, averaged over three years and 2) an annual standard at a level of 53 ppb, originally established in 1971.  EPA last reviewed the NO2 standards in 2010.  The schedule for the current review was set by a court order that requires a signed proposed determination by July 14, 2017 and a final determination by April 6, 2018.  The proposal to retain the current standards was signed by the EPA Administrator on July 14 and will be subject to a 60-day public comment period upon publication in the Federal Register.