Interesting that there is an observable correlation between detected radiation and the air quality. You can see how the peak CPMs match up with the peaks in air pollution. Note the scale of air quality is pretty tight, going from 4.0 to 5.5 PM2.5 ug/m^3, which is all in the very good range.

It is also possible that the correlation is only with the time of day for both of them. The peaks are both more often in the mid to late evening. This could be a result of the daytime/nighttime temperature variation effecting the muon decay rates, which are a large source of overall cosmic ray observations… however CRs only account for 10-15% of typical measured background radiation. Radionuclides in dust could also be a factor.