For all those commenting on 'aren't more polluted areas just more criminal due to other factors", as far as I can tell the researchers examined crime rates for the same place and find correlation with whether there was more Ozone and PM 2,5 on a particular day or not. So they are not comparing clean air neighborhoods to highly polluted neighborhoods, but the same neighborhood on different days. https://www.sciencedai…
People should just stop doing this kind of studies, we are just not equipped with powerful enough mathematical tools yet to deal with this kind of highly entangled phenomenons (and we often don't have the data either, collecting and curating it would be an interesting and useful research topic by itself).