Chinese air pollution: Clearing the air? IT WAS China's former leader, Deng Xiaoping, who urged his countrymen to "seek truth from facts." But for the many in China who distrust government data, that sage advice can be hard to follow. In the case of official reports about the improving air quality in Chinese cities, however, taking Mr Deng's advice is easier. To evaluate a specious government report of yet another "blue-sky day," you need only look out the window, sniff the air, or - for the brave - take a deep breath. In Beijing recently the facts have been speaking for themselves. Smog is often so bad that residents cannot see buildings just across the street, schools cancel outdoor activities and the airport cannot operate. For those who do not trust their own burning eyes and scratchy throats, other sources of information are available. A controversial monitoring station at the American embassy in Beijing has for several years been issuing hourly reports from that single location. Chinese pressure groups have also begun monitoring campaigns of their own, and all these readings have been widely distributed over Chinese websites and social media, including the vastly popular Weibo microblog platform. Despite their methodological failings, they have been enough to arouse public ire and now to force a change. Beijing city officials announced on January 6th that by month's end they would start reporting readings on "PM 2.5" - particulate matter that measures 2.5 microns or less in diameter, fine enough to enter deeply into the lungs and bloodstream and cause the most serious health problems. China's failure until now to report on PM 2.5 has been an important source of the discrepancies between official reports and the acrid, airborne reality. Officials have been monitoring PM 2.5 for years on a "pilot" basis, and had planned to wait until 2016 to start publishing those readings. Ma Jun, of China's Institute of Public and Environmental Affairs reckons the public outcry goes a long way to explain why the authorities decided to act sooner, despite official concerns about the capital's image. "With amazing speed, this term of technical jargon, PM 2.5, became a household word," says Mr Ma. People understood the huge impact on health, he says, and their fuss helped overcome the barriers to transparency. According to Deborah Seligsohn, an adviser at the Beijing office of the World Resources Institute, a think-tank, environmental officials have adopted a sophisticated, sustained strategy of enlisting public opinion against the polluters in support of tighter regulation. And, she says, they have achieved greater success than Chinese or foreign critics give them credit for. The European Union only started reporting on PM 2.5 in 2008, and the United States just six years earlier. In results confirmed by external experts, she says, China exceeded its ambitious targets for sulphur reductions in its most recent five-year plan. Success will require enforcement as well as public reporting. Ms Seligsohn predicts that Beijing residents will need to wait before seeing improvements. Raising air quality took 25 to 35 years in America, she says. The city of Los Angeles has been regulating its air quality since the 1950s and has never yet met federal standards. "In China," she says, "they are hustling, and doing things pretty quickly, but they started a lot later and it just takes time."