How particle size effects air pollution rankings in large cities
It's important to note that this is regarding particles that are 2.5 micrometers or smaller in diameter per cubic meter.
It's important to note that this is regarding particles that are 2.5 micrometers or smaller in diameter per cubic meter. When accounting for PM10 (particles 2.5 - 10 micrometers in diameter per cubic meter) it's a dramatically different picture.
On the right side of this screen you can download the entire .xls database of 1600 cities and look at it yourself.
The most polluted city in China by this database is Langzhou, in both the PM10 and PM2.5 categories. From what I can tell this places that city as:
Tied for 38th most polluted city in PM10 (with 155)
34th most polluted city in PM2.5 (with 71)
Interesting that it gets so much of the press.
I don't pretend to know a lot about the various health risks tied to either category, but I think it's important to note the difference.
Most cities have a lot more PM10 than PM2.5
For example a city in Bahrain has PM10 at 244 (13th) but PM2.5 way down at 58 (not even top 50).
But then there is a city in India that is only at 67 PM10 (not even top 100 and less than Fresno, California), while at 88 PM2.5 (18th and on this list).
By ranking these countries at 2.5 over 10, it changes the list quite dramatically. At PM10 the most polluted cities hands down are in Pakistan and Bahrain (reaching as high as 540, where India tops out at 329), although India does have two in the top 10. I had the idea when doing this that maybe the guy they were trying to disprove was talking about PM10 but he would be far more incorrect there.
TL;DR it depends what particle size of pollution you use, or Pakistan, Iran, and Bahrain dominate the top 10. China's most polluted city barely hits the top 40 either way.
As an extra note, the reason that China has hit so hard in the news lately is because Beijing and some other cities are in an extreme alert, with pollution levels much higher than anything listed in the OP. This report is based on averages taken over previous years by the World Health Organization..