By Lucy Hornby and Wan Xu
BEIJING (Reuters) - Beijing began disclosing the amount of tiny pollution particles in the air on Saturday, in a move that could improve disclosure but alarm a public barely resigned to the capital's choking smog.
The new measurement of particles of 2.5 micrometers or less in diameter, or PM2.5, comes after growing attention to air quality in Beijing, one of the world's most heavily polluted capitals, from Chinese as well as foreigners.
"So that the people can form a relatively complete understanding of the Beijing air quality, the Beijing Municipal Environmental Monitoring Center will publish hourly 2.5 data from January 21," the center said on its website, www.bjmemc.com.cn.
On Saturday, a clear crisp day that contrasted with the thick smog earlier in the week, the Beijing Center reported between 0.003 micrograms-0.062 microgram per cubic meter of PM2.5 particles in the air, Xinhua said.
"It shows that the government is responding to popular concerns about air pollution," said Steven Andrews, an environmental consultant who has studied Beijing air pollution since 2006.
"It's a recognition by the government that the way it was monitored and reported in the past didn't reflect people's perception of how serious the problem is."
The data will be collected from a monitoring station in the Chegongzhuang area of the second ring road, which encircles the center city, the Xinhua news agency said.
Chinese experts had earlier criticized as "unscientific" a single monitoring point on the roof of the U.S. Embassy, which releases hourly air quality data via a widely followed Twitter feed.
China previously disclosed readings only of pollutant particles that are 10 micrometers in diameter or larger. Doctors warn that the tiny floating PM 2.5 particles can settle in the lungs more easily and cause respiratory problems and other illnesses.
Earlier in the week, the U.S. Embassy labeled the air pollution in Beijing as hazardous after its PM2.5 reading topped its maximum reading of 500 micrograms per cubic meter.
A reading of 250 or above over a 24-hour period is hazardous, according to the U.S. Environmental Protection Agency.
Environment Minister Zhou Shengxian said in December that China would begin nationwide collecting of PM2.
While Beijingers complain, serious soil and water pollution also plagues the rest of the country.
On Saturday, firefighters in the southern region of Guangxi sprayed 80 tonnes of aluminum chloride, a neutralizing agent, into the Longjiang River after levels of the heavy metal cadmium were found to be three times the official limit, Xinhua said.