The capital's environmental protection bureau started gauging public opinion on upgrading emission standards for lightweight automobiles on Monday in an attempt to cut vehicle pollution in the city.

The tighter standard will for the first time set the emission limit for particulate matter pollutants to further reduce the automobiles' contribution to the city's concentration of PM 2.5 (particulate matter smaller than 2.5 micrometers in diameter).

Along with the new standard, the emission limit for four pollutants will also be tightened, including carbon monoxide, hydrocarbons, oxynitride and particulate matter.

According to the draft, the oxynitride will see the sharpest drop in emission limits, reducing from the current strictest 0.08 grams per kilometer to 0.06, a 25 percent decrease. Oxynitride turns into particulate matter pollutant through chemical changes and is a major contributor of the city's PM 2.5 concentration, said the bureau.

The new limits, once adopted, will be in accordance with the standard currently adopted in Europe.

The capital plans to take the lead in adopting tighter standards, according to the bureau.

Feedback will be summarized on April 9.