Thick smog shrouds China's capital, Beijing. There has been a public outcry over the methods authorities use to measure air quality, and Beijing residents say official figures understate the severity of the pollution. Local authorities publish readings of pollutant particles 10 micrometers or more in diameter, and last month said they had met their target for "blue sky" days in 2011. 　　But a spokeswoman for Greenpeace says the measuring system is out of date. 　　Greenpace Campaigner, Zhou Rong: "Some gaseous pollutants have turned into solid pollutants. The old pollutant standard to evaluate our air is already out-dated. So if we talk about an improvement of the air quality according to that standard and that we have 'blue skies', it is very inconsistent with how the public is feeling." 　　Under stricter standards to be introduced in the Chinese New Year, the municipal government will also monitor and provide updates on the smallest, most dangerous pollution particles. Known as PM 2.5, these air particulates are 2.5 micrometers in diameter or less, [5]which doctors say can more easily settle in the lungs and cause illness. 　　Parents worry that air pollution is endangering the health of their children. Li Feigyong: "The children are so young right now. If the air quality gets worse, it will kill our next generation. 　　The government is now monitoring PM2.5, for the healthy growth of the next generation. It has made many efforts. As citizens, we hope the government can worker harder." 　　The pollution is caused by a cocktail of smokestack emissions, vehicle exhausts, aerosols, and dust, and has at times blanketed the city in such heavy smog that flights have been cancelled. (Nick Rowlands/Reuters)