I haven't checked recently, but back in 2015 (or 16) I checked the actuals for the previous completed year on "small particulate matter of 2.5 microns or less in diameter (PM2.5)" air pollution against WHO standards (note many regard this type of air pollution to be most directly hazardous to human health). I checked the official Shanghai numbers, the numbers measured and published by the US Consulate in Shanghai, and the official numbers for Los Angeles.
At the time, the Chinese had stopped publishing official numbers for small particulate and had adjusted their red/yellow/green daily scoreboarding on the larger particulate to a, um, unique standard that was much less stringent. Using the US Consulate numbers, Shanghai was above even marginally acceptable small particulate levels (using WHO standards) for well over 300 days the previous year. Going from memory, but I believe it was >320 days. LA, during the same time period, had fewer than 20, I believe it was around 8 or 12 days. It is possible, of course, that the US Consulate numbers were inflated for propaganda purposes (as the CCP frequently implied), but virtually every expat (mainly from EU but also from South Africa, Australia, Canada, and the US) and most Chinese people I knew felt the US numbers were reasonably accurate and were greatful for their daily publication.
I watched all this closely during the time I lived there, of course. I have asthma, so my interest was more than academic. Interestingly, in most places in Shanghai, I found the air pollution at ground level was much, much better than that even 3 or 4 floors off the ground. I assumed this was due to constant motion of people and vehicles on the ground - much like cars and trucks on a freeway will punch a tunnel through even a fairly heavy fog.
www.cnn.com
Delhi
. Unfortunately yesterday they have told us not to return to work in the corporate office area unless it's an emergency. Had someone develop a fever overnight that was still working out of the corporate office. 
