Beijing's real-time report on PM2.5 levels has led to complaints from academics and the public over a "lack of detail".

The capital’s environmental monitoring center, which has 35 stations citywide, began releasing hourly updates on PM2.5, or particulate matter smaller than 2.5 micrometers in diameter, on Saturday, along with its usual reports on sulfur dioxide, nitrogen dioxide and PM10.

However, air quality readings on its website — bjmemc.com.cn/g356.aspx — are only available for the previous 24 hours.

Even academic researchers cannot access historical data, said Li Jinfeng, a PhD student at Peking University’s College of Environmental Sciences and Engineering.

"Many regions, including Hong Kong and Taiwan as well as cities in the United States and Europe, provide a download service for air-quality data, so the public can access information at any time and for any location," she said. "It is not necessary for the government to keep the data secret as it has already been released to the public."

Zhao Kunxue, a 28-year-old accountant from Beijing, added: "You can hardly see whether the air quality has improved or not without comparing it to the past. Even if I know the concentration of the area I am in, I can hardly make any sense out of it with all these figures."

The government must develop more direct public information channels and straightforward descriptions of air quality, said Wang Qiuxia, a researcher at Green Beagle, an environmental protection NGO in Beijing.

The environmental monitoring center could not be reached for comment on Sunday.

The PM2.5 monitoring network is being trialed for three months, with a view to the capital’s environmental protection bureau adopting it as a measure for assessing air quality next year.

For the first time, Beijing has also placed five monitoring stations beside roads, to record how traffic pollution affects air quality.

However, the results at individual stations do not represent conditions across the whole city, the center said.

Roadside monitoring stations may help further environmental research and management in the future, Wang said.

Vehicles are major contributors to PM2.5, which can trigger cardiovascular and respiratory diseases.

The number of automobiles in Beijing now exceeds 5 million.

According to the city’s environmental protection bureau, the density of PM2.5 has decreased over the past 10 years, with the average annual density falling from between 100 and 110 micrograms per cubic meter of air in 2000 to between 70 and 80 mcg/cu m in 2010, due to pollution reduction measures, including a policy to encourage the scrapping of old cars.

City officials are determined to cut the concentration to 60 mcg/cu m by 2015 and by a further 10 mcg by 2020.

In addition to roadside stations, Beijing has also placed six stations close to borders with neighboring regions. These will study how much neighboring cities and provinces influence the capital’s air quality, Wang said.

According to Beijing’s environmental protection bureau, 24.5 percent of PM2.5 pollutant comes from neighboring provinces.

Data collected on Saturday shows the density of PM2.5 in Beijing’s southeast and southwest suburbs, which border Tianjin Municipality and Hebei Province, is much higher than readings collected in downtown Beijing.

"The capital has two recognized pollution transmission channels: one is in the southeast and the other is in the southwest," Beijing Times quoted Xie Shaodong, a professor at Peking University’s environmental sciences college, as saying on Saturday.

"It is very likely the two regions see a comparatively higher PM2.5 reading."

The Ministry of Environmental Protection has ordered 74 cities to apply more comprehensive air-quality monitoring standards, including for ozone, carbonic oxide and PM2.5, and publish daily records on PM2.5 levels by the end of the year.

Cities in the Beijing, Tianjin and Hebei region, Yangtze River and Pearl River deltas, Southwest China’s Chongqing and all provincial capitals, have also been ordered to publish the results of air pollution monitoring by the end of the year.

zhengxin@chinadaily.com.cn