China learned about fine particles and the risks they pose after heavy smog and haze descended on many areas of the country in January.

But experts say another group of organic chemicals - volatile organic compounds that can be even more disruptive - are also hidden in the smog. These are the next pollutants targeted in the government cleanup.

Shortened to VOC, total emissions from this group of chemicals are among the preconditions determining whether a construction project can pass its environmental impact assessment for the first time.