Beijing has seen a decline in PM2.5 density besides the decrease of the PM10 density during the past decade according to some relevant research data, Beijing's Municipal Environmental Protection Bureau said Friday.

The average annual PM2.5 density in Beijing has reduced from 100-110 micrograms per cubic meter of air in the year of 2000 to 70-80 micrograms per cubic meter in 2010, said Yu Jianhua, an official with the bureau.

The downtrend still continues at present, Yu said.

Although Beijing did not monitor air-quality using the PM2.5 gauge ten years ago, the undisclosed PM2.5 data is available for laboratory use, according to Yu.

China currently uses PM10, or particular matter under 10 micrometers, to measure air quality, but the public has urged government authorities to apply the tighter PM2.5 standard, which measures finer matter that is considered more hazardous to people's health as it can go deeper into the lungs.

The Ministry of Environmental Protection said it has been considering revising present standards and a new index standard which includes the measuring of PM2.5 and ozone density is scheduled to be fully implemented nationwide in 2016 with pilot projects conducted in certain regions ahead of the national deadline.