Beijing has released a draft of new exhaust emissions, considered the world's toughest standards on light-duty vehicles, which will take effect on Dec 1, 2017, the municipal environmental watchdog said on Thursday.

The capital currently adopts national V standards, which are the toughest in the country.

The draft new standards will raise the bar to further cut emissions, because they are the prime source of air pollution in the capital, contributing to 31 percent of pollutants, the Beijing Municipal Environmental Protection Bureau said.

For light-duty vehicles, the coming national VI emission will reduce by 40 percent current standards. Beijing has followed the world's toughest restriction, enforced in California, making the new capital standards also the world's toughest, the bureau said.

In addition, the new standards will reduce emissions from heavy-duty vehicles, such as trucks, by 50 percent compared to current standards.

The draft has been released on the official website of the bureau, and will solicit public opinions until Dec 25.

If the new standards take effect, half of vehicles will see their exhaust cut by 50 percent in four to five years, the bureau said, adding that by 2022, the capital will reduce by 20 to 30 percent exhaust emission from all vehicles.

The capital is presently home to more than 5.5 million vehicles, which will increase by 600,000 annually, the bureau said.