The Chinese capital of Beijing has seen frequent hazy days this winter.

Amid mounting public concern over worsening air quality, the municipal government launched the much-expected PM 2.5 measure of air quality Saturday.

The tighter air quality measure is part of Beijing's effort to control pollution.

From Saturday morning, the PM 2.5 data is available on the website of Beijing Environment Protection Monitoring Center.

SOUNDBITE (CHINESE) ZHAO YUE, MONITORING CENTER DEPUTY CHIEF:
"The data will be updated once in an hour. You may also see the variation trend."

The figures are based on the data from the center, which located on the Second Ring Road.

The PM2.5 gauge is considered stricter than Beijing's previous standard of PM10, as it monitors "fine" particles 2.5 microns or less in diameter.

In fact, the monitoring center started monitoring PM 2.5 for research use in 2006.

As the public start to pay more attention on the air quality issue, Beijing's environment authority decides to publish the PM 2.5 data for public reference.

SOUNDBITE (CHINESE) ZHAO YUE, MONITORING CENTER DEPUTY CHIEF:
"The PM 2.5 gauge is still on the experimental stage. In the future, we're supposed to provide a compound air quality index, which is based on a batch of measurements including the PM 2.5. Since the whole monitoring system has not been fully established, the published data is only for reference."

The official said the current form of data releasing is subjected to change according to a national standard on air quality measurement in the future.

Since the start of this winter, Beijing has seen more smog-shrouding days.

Public discontent was further fueled by discrepancy between the government's official data and the U.S. Embassy's measurements.

In late November, the U.S. Embassy in Beijing rated the city's air as "hazardous" based on its PM 2.5 measurement, while the Beijing Municipal Environmental Protection Bureau said the pollution was "slight."

Many citizens have urged the government to adopt the tighter PM 2.5 standard suggested by the World Health Organization.

In response, the Beijing municipal government promised to provide hourly updates of PM2.5 measure ahead of the lunar New Year, which falls on January 23.

China's Ministry of Environmental Protection also pledged to revise the present air quality standards and add the PM 2.5 gauge in the measurements.
Beijing is now working to increase its number of monitoring substations and plans to implement the new standard by 2013.

The new standard is expected to be fully implemented across China in 2016.