A lot of this pollution is just a remnant from when China's economy was still largely manufacturing-based. Now that this percentage is beginning to change, (mid 30s in mid 2000s down to high 20s now), the government seems earnest in their attempts to curb pollution.
See:
http://www.businessinsider.com/china-pollution-business-oppo...
http://uk.reuters.com/article/2013/01/31/china-diesel-standa...