The 2012 Annual Report on Motor Vehicle Pollution Control in China, released Thursday, emphasized a growing trend of compound sources in the country's air pollution.

Tao Detian, a spokesman for the Environmental Protection Ministry, said the number of motor vehicles nationwide in 2011 was at more than 200 million, 30 times more than the 1980 level. The total amount of emissions also rose 14 times, he said.

Of all the motor vehicles, only less than 6 percent qualified for the national standard IV for vehicle emissions, the strictest level applied in China, but only in some cities such as Beijing, Xi'an and Chengdu.

The report said that China was the largest producer and seller of motor vehicles in the world for three continuous years. Motor vehicle exhaust emissions have become the second most important source of air pollution next only to coal burning.