Beijing will be the first Chinese city to publicize hourly air quality data based on the so-called PM2.5 standard, which measures particles smaller than 2.5 microns that cause the most serious health problems because they get deep inside the lungs. Chinese authorities now publish data that measure 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 last few years.
Beijing is ranked as one of the world's most polluted cities by the World Health Organization and is regularly shrouded in choking smog that grounds flights, forces parents to keep children indoors, and causes widespread respiratory problems. 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. (WSJ, 1/7/2012)