In major cities in the US, I've found that PurpleAir is a much better resource for checking local air quality. Air quality varies significantly, and the EPA on

In major cities in the US, I've found that PurpleAir is a much better resource for checking local air quality. Air quality varies significantly, and the EPA only has very sparse monitors. PurpleAir San Francisco: https://www.purpleair.com/map?&zoom=12&lat=37.7&lng=-122.4 https://www.purpleair.com/map?&zoom=12&lat=37.7&lng=-122.4