Primary National Ambient Air Quality Standards (NAAQS) for Nitrogen Dioxide
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On April 6, 2018, based on a review of the full body of scientific evidence, EPA issued a decision to retain the current national ambient air quality standards (NAAQS) for oxides of nitrogen (NOx). The EPA has concluded that the current NAAQS protect the public health, including the at-risk populations of older adults, children and people with asthma, with an adequate margin of safety. The NAAQS for nitrogen oxides are a 1-hour standard at a level of 100 ppb based on the 3-year average of 98th percentile of the yearly distribution of 1-hour daily maximum concentrations, and an annual standard at a level of 53 ppb.