China new vehicle sales and production chart from 1994 to 2010.

"Emission intensity per unit GDP (100 million yuan) in China has declined in recent years. However, the total emission volume has risen due to GDP growth," he said.

International Council on Clean Transportation founding chairman Michael P. Walsh pointed out several outstanding changes. "One of the important changes is the adoption of the PM 2.5 standard which didn't exist 13 years ago, as well as the shift from coal-based air pollution to vehicle-based pollutants," he said. "Since vehicles by their nature are mobile, it creates the need for a national provision to ensure fuel quality."

China overtook Europe in vehicle sales in 2012 and the US in 2009.

Beijing and Shanghai PM 2.5 source pie charts show that motor vehicles contribute over 20% of PM 2.5 polluiton. [Provided by Michael P. Walsh]

Carbon monoxide, nitric oxide, nitrogen dioxide and other pollutants emitted by motor vehicles are among the major contributors to air pollution problems that frequently occur in Chinese cities.

In response to the above-mentioned problems, the State Council issued a timetable to upgrade fuel quality, aiming to implement a strict standard nationwide by 2017 in its latest bid to reduce pollution.

The country will issue a '5th-phase' standard for automobile petrol, with sulphur content within 10 ppm (parts per million) before the end of the year. There will be a grace period until late 2017, according to an executive meeting of the State Council chaired by premier Wen Jiabao in February, Xinhua reported.