Beijing environmental authorities yesterday began releasing hourly air pollution readings for PM2.5 - health-threatening fine particles with a diameter less than 2.5 microns - fulfilling a promise of publicising them before the Lunar New Year, under intense public pressure.
The readings of one monitoring station at Chegongzhuang in Xicheng district were updated hourly with about three hours' delay on the website of the Beijing Municipal Environmental Monitoring Centre.
Releasing PM2.5 data was perceived as a move to appease residents angry about the government's prolonged secrecy over the city's deteriorating air quality. Beijing authorities have long measured PM10 levels, meaning particles with a diameter of 10-microns or less. But PM2.5 are considered more critical as these smaller bodies can embed themselves deep in the lungs and even enter the bloodstream.
They can cause cancer and extreme respiratory problems.
The US embassy conducts its own monitoring, in Chaoyang district, and publishes its PM2.5 readings on Twitter, winning praise from the public while giving Chinese authorities a headache.
Analysts applauded the move as a step forward in environmental-information disclosure because residents would be better informed about air quality. The government had fulfilled its commitment, they said, which helped restore its credibility.
However, the readings were obtained from only one of the city's six monitoring stations equipped to take PM2.5 readings.
'The readings at one station cannot represent the whole city's air conditions, but they still serve as an important reference for the public,' said Ma Jun, head of the non-government Institute of Public and Environmental Affairs. 'I hope the government can disclose data from other stations soon.'
A Beijing official said the government had monitored PM2.5 levels since 2006, but the data was collected mainly for research.
The government said it hoped to install equipment for taking PM2.5 readings at all 27 monitoring stations and release real-time figures by the end of this year.
It was sunny with a blue sky and some wind yesterday. The official reading at 12pm yesterday showed 0.015mg per cubic metre while the US embassy reading was 0.018mg per cubic metre, or a measure of 57 on the Air Quality Index.
The US data fell into the category of moderate health concern, which means people with respiratory or heart disease, the elderly and children are groups most at risk, according to Air Now, a website designed to provide air-quality information.
Smog plagued the capital on Thursday as the United States embassy readings at 3am and 11pm exceeded 0.5mg per cubic metre, categorised as 'hazardous for the entire population'.
Ma said that the rapid development of the city powered by coal-burning electrical plants, a growing number of cars, dust from construction sites and emissions from surrounding heavy-chemical industries had offset efforts taken by the authorities at improving air quality.
Professor Zhu Tong , head of Peking University's centre for environment and health, said that it would take some time to see the results of efforts taken to improve air quality. 'The air can be improved when the new sources of pollutants are fewer and government takes greater steps to counter their effects,' he said.
Rise in PM2. 5 concentrations in the capital yearly since 1998, the Chinese Academy of Sciences was quoted by state TV as saying last month