BEIJING

 A Chinese provincial government is preparing to adopt its sixth phase emissions standard, which it says will be the world's strictest.

State news agency Xinhua reported Friday that the Beijing Environmental Protection Bureau is due to implement the new standard from Dec. 1, 2017.

The bureau's statement said it will cover light vehicles, heavy vehicles and heavy motors.

At present, Beijing vehicles need to meet the fifth phase of the emissions standard, approximately equivalent to the Euro V emissions cap.

"According to the sixth phase standard, light vehicles must cut emissions by 40 percent, and heavy motors, such as those used in buses, must cut emissions by 50 percent," the statement said.

It also added that research had shown that "fine particles" less than 2.5 micrometers in diameter -- which are believed to pose the greatest health risks -- make up 31 percent of the total pollutants.

The bureau claims these measures will mean that the total pollutants emitted by all vehicles in Beijing will be cut by as much as 30 percent by 2022.

Smog has become a major environmental issue in Beijing.

The central government has ordered the city to cut the number of fine particle pollutants by 25 percent from 2012 levels by 2017.

China was the leading CO2 emissions producer in 2014, producing 23.4 percent of global emissions, followed by the United States, which produced 14.7 percent.

No other countries produce more than 5 percent.