The list is bulls**t political correctness.
Los Angeles and Phoenix in the U.S., along with London U.K., make the list because of "ozone" levels, stupid projections of long term harm over a lifetime, etc. I'm sorry... total crap. Compared to Beijing and other cities where you can't go out of your apartment on days without falling down dead or wheezing like an addicted smoker, these projections of ozone and long term health are silly.

Although I do not dispute factoring in ozone, I also agree the list seems pretty lame.

Tokyo and Mexico City - days when you cannot go out without masks. What of the other SE Asian and South American mega-cities?

The list seems a hodge-podge to get an article out.

A standard using internationally recognized air quality indices would give a more informative ranking. Water pollution needs to be dealt with separately as does toxic waste.

Don't know the current rankings, but New Jersey in the States has traditionally had the most toxic waste "Super Fund" sites (designated by our government as most polluted land; heavy metals, etc.).

I live in a countryside like area outside of Atlanta. Nice air here, but get on the expressway heading into Atlanta and the air quality is rated as among the worst, if not the worst, in the US due to high traffic.

Beijing when the sandstorms hit has to be up there. But no doubt that one Chinese city listed is number one for air pollution in the world; it appears on every list at the top. Why do they let people live there?

And you know that picture in the middle of the list with the couple wearing the filtering masks was staged. It just looks like a pair of hippie phags trying to show their dedication to new age environmental socialist paganism .

But some of those places really are crap.

I saw a documentary about beijing in 1978 and now.
Beijing has become a totally different city.
When the population was not so crowded, beijing was a leisurely and comfortable city.
The real beijingers said: Piss off, WaiDiRen(strangers)!!!

I smell payoff.