[burger]

Okay, here's a much much better study of air pollution effects on mortality in the US: https://www.medrxiv.org/content/10.1101/...20090746v1

tl,dr: NO2 (nitrogen dioxide) was associated with moderately higher death rates.  I.e., going from the average NO2 level in the US to the top 25 percentile would increase death rates about 7% (that's percent, not percentage points).  Ozone and PM2.5 had no effects.

This study dotted all their i's, etc.  I just skimmed it, but I don't see any major flaws.

NO2 tends to be highest near big cities.

[burger]

Okay, here's a much much better study of air pollution effects on mortality in the US: https://www.medrxiv.org/content/10.1101/...20090746v1

tl,dr: NO2 (nitrogen dioxide) was associated with moderately higher death rates.  I.e., going from the average NO2 level in the US to the top 25 percentile would increase death rates about 7% (that's percent, not percentage points).  Ozone and PM2.5 had no effects.

This study dotted all their i's, etc.  I just skimmed it, but I don't see any major flaws.

NO2 tends to be highest near big cities.