Today the Environmental Protection Agency (EPA) strengthened the PM2.5 annual health National Ambient Air Quality Standard (NAAQS) to 12.0 (µg/m3), which since 1997 has been 15.0 µg/m3. With respect to the 24-hour health standard (primary standard) for PM2.5, it continues to be at 35 µg/m3 since 2006. The agency also retained the existing standards for coarse particle pollution (PM10). You can read the press release, some fact sheets and the final rule document here.
Moderate levels of PM2.5 were observed today in many parts of the US (right), including the Northern Plain States, the Midwest, Northeast and also in California. Code orange was observed in Pennsylvania, New Jersey, Vermont, Massachusetts, Northern California and also in Eastern Canada, between Montreal and Quebec City.
OMI shows high tropospheric NO2 concentrations over the regions in the East that experienced moderate to unhealthy PM2.5 concentrations today (left).