As development comes first, and China took the path of making itself the World's Factory, it also turned itself into the world's trash can. Last week the result was a smog layer covering large parts of the country's East. Most monitoring stations went off the scales, and you could actually taste the air instead of smelling it. Environmental laws are strict in China, but there is not much implementation.
Beijing's three core virtues are corruption, pollution and congestion. And all three have something to do with each other. Living is not cheap in Beijing, but life is. This is a very stable atmosphere to trap emissions and a large incentive to cover things in a foggy environment. Air pollution in Beijing is not a meteorological problem.