US standards on NO2 remain

After a review of scientific evidence, the US Environmental Protection Agency (EPA) on 14 July proposed to retain the current national ambient air quality standards (NAAQS) for nitrogen dioxide (NO2).

The NAAQS for NO2 are a 1-hour standard at 100 parts per billion (ppb), based on the 98th percentile of the annual distribution of daily maximum 1-hour NO2 concentrations averaged over three years, and an annual standard at a level of 53 ppb.

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