Oddly enough I spent a few months in China and there was blue skies when it wasn't raining.
There tends to be a lot of Asians, all over the world, who wear the face mask.
So my question is are those pictures of real smog or is it fog or something else? I've heard that it was supposed to be filthy in China but my experience was the opposite.
In Japan, they wear the face masks if they're sick. It's seen as a courtesy to others, so you don't spread your germs around. I would assume it's probably bled through to other cultures.
In Mainland China, the pollution is so bad because all the factories still run on coal. Not the clean coal technology we use here either. Beijing is basically like a supersized version of Dickensian London. While they're a nuclear nation, coal is still a lot cheaper.
Not all cities are that bad. Shanghai is working to bring pollution down. The rich people are starting to get tired of all the smog, so there's incentive to invest in anti-pollution initiatives.
Off the mainland, Hong Kong and Macau are both fairly clean cities by Chinese standards. Over in the Republic of China (Taiwan), Taipei looks no worse than your typical North American cities from what I've seen.
Japan is very neat and orderly. Really puts all of us to shame. Especially given the population density.
India, well... I spent a good three years working on and off in our "Little India". They don't have a reputation here for being the cleanest people. That combined with the holier than thou attitude many of the FOBs have. I've often joked that dislike for them is the only thing whites, blacks, and Asians have ever agreed on. Should hear my Grandma's Chinese neighbour rant about the family that moved across the street. Even other Indians (who've been here a few generations) can't stand them.