Authorities in China's notoriously smoggy capital have announced that they will start publishing more accurate data on air pollution this month, bowing unexpectedly to a social-media campaign driven by the U.S. Embassy publishing its own data via Twitter.
Beijing will be the first Chinese city to publicize hourly air-quality data based on what's known as the PM2.5 standard, which measures particles smaller than 2.5 microns. These cause the most-serious health problems because they get deep inside the lungs. Chinese authorities now publish data on larger air particles, of up to 10 microns in diameter.
The decision represents one of the most significant examples yet of Chinese authorities' yielding to public pressure exerted principally over the Internet via microblogs, which are similar to Twitter and have become hugely popular over the past few years. It comes less than three weeks after a public appeal by Vice Premier Li Keqiang for local governments to use the PM2.5 standard, which most experts recommend.
The appeal of Mr. Li, the favorite to become premier in a leadership change starting late this year, reflects concern among Communist Party leaders about growing public anger over environmental issues, especially air pollution, analysts say.
Beijing residents have become increasingly aware that the official air-quality readings are consistently more positive than the PM2.5 data, which the U.S. Embassy has been tweeting since 2008.
On Friday, the U.S. Embassy's tweets called Beijing's air 'very unhealthy' for most of the morning, and 'unhealthy' in the afternoon. Beijing's official reading for the entire day was 'good'─the second-best category, which officially makes it a 'blue-sky day.' Officially, Beijing enjoyed 286 days of 'blue skies' in 2011, up from 252 days in 2010.
The Beijing Municipal Environmental Protection Bureau said late Thursday that it would start providing hourly PM2.5 readings on its website by the start of the Lunar New Year on Jan. 23. The national government had previously said PM2.5 readings were only for internal use and did not have to be made public until 2016.
The surprise decision was announced following a tour of Beijing's air-quality-monitoring facilities by Environment Minister Zhou Shengxian. He was quoted on his ministry's website on Friday as saying: 'The state of Beijing's air quality relates to the national image and the physical and mental health of the capital's 20 million people.'
Environmental activists and experts said they expected several other Chinese cities to take similar steps this year, although some expressed concern about how precise the new readings would be, and whether they would prompt the government to curb air pollution.
'This does come as a surprise,' said Li Yan, head of the climate and energy campaign for environmental group Greenpeace in East Asia. 'It's an encouraging sign. But at the same time, it's only the first step because the public is still very worried about air quality and getting to know the data doesn't solve the problem. It's action that is needed.'
Some analysts say the credibility of party leaders is being undermined by the frequent discrepancy between official statements and statistics and independent information that is increasingly available online, despite the efforts of China's Web censors.
Beijing, ranked by the World Health Organization as one of the world's most-polluted cities, is regularly shrouded in choking smog that grounds flights, forces parents to keep children indoors and causes widespread respiratory problems. Yet Beijing authorities maintain that air quality has been steadily improving, and regularly report 'blue-sky days' even when no blue sky is visible.
Even based on China's PM10 readings, 32 of its cities that track pollution fall short of WHO standards, according to a report on air pollution world-wide that the agency published in September.
Beijing was the fifth-worst with average annual levels of 121 micrograms per cubic meter of air, compared with a global average of 71 and a recommended level of 20. The most polluted city in the U.S. based on PM10 was Bakersfield, Calif., with an average of 38 micrograms, according to the WHO report.
Beijing's decision represents a victory of sorts for the U.S. Embassy, which, according to U.S. diplomatic cables published by WikiLeaks, came under pressure from Chinese officials to stop publishing its data. Some Chinese officials, and experts, publicly called the embassy's readings inaccurate, noting it has only one monitor and did not use exactly the same methodology as the U.S. Environmental Protection Agency.
A spokesman for the U.S. Embassy said Friday: 'We have an ever-expanding collaborative relationship with our Chinese counterparts in the environmental arena. One aspect of this collaboration is in mitigating air pollution.'
He said the Embassy had recently added the phrase 'at 24-hour exposure at this level' to its readings, to clarify how they should be interpreted, and bring them into line with EPA standards.
Another key player in the social-media campaign was Pan Shiyi, a billionaire property developer, who launched an online vote in November via his microblog on whether China should use PM2.5. Tens of thousands of people voted in favor. 'Good news!' wrote Mr. Pan on his microblog Friday, in response to another message from his wife, Zhang Xin, saying: 'We have saved our air! Knowing the truth is the first step. After that there will be all kinds of solutions.'
从某种意义上说，北京决定启动PM2.5监测是美国大使馆的胜利。据维基解密网站（WikiLeaks）公布的美国外交电文显示，中国官员曾向美国大使馆施压，要求其停止发布PM2.5数据。部分中国官员和专家公开宣称美国大使馆的数据不准确，指出其只有一个监测装备，且使用的监测方法同美国环境保护署（U.S. Environmental Protection Agency）使用的方法并不完全一致。