[contingencies]

The part of the city the reading was taken and time of day seems to play a huge factor.

For example, the previous posted said Paris was 24, Paris - where I am now, with the window open, slightly after midnight - is currently reporting 53.

Kunming, a city of 6+ million where I usually live in China's southwest, is a little higher at 68. (This counters the 'China is dirty' western media BS)

Sydney, where I grew up, is higher at 75. However, in another reading closer to the area of town where I used to live it's much lower at a mere 13.

So, check which part of the city you are looking at and what time of the day the reading was taken. Also, don't assume all of China is all dirty and horrible like the east coast megacities (though much of it may be, to varying extents).