The WHO recently released a report where Delhi was fingered as the most polluted city in the world.
Having been to both Delhi and Beijing, this seems odd. Delhi is polluted, but Beijing seemed to be in a class all by itself. In Beijing, visibility was in the tens of meters. Delhi is bad, but it never seemed that bad -- you can always see what's on the other side of the street.
Contrast these two pictures, both taken in summer in the city centers of the two cities:
Two possibilities that I can think of:
(1) Perhaps the Beijing numbers reported to the WHO are "cooked"?
(2) Perhaps the pollutant mix is different, and the Beijing pollutants are more visible and more likely to remain suspended in the atmosphere?
And just to provide some contrast in terms of the distance one can see on a summer day in the center of the city: Kathmandu, Paris and New York:
Of the three cities above, Kathmandu was the dirtiest. I found it dirtier than Delhi. Once you get out of the city, though, the Nepali countryside is gorgeous. But we are talking only about cities here.