PM2.5 is a measurement of small particulate matter in the air, and until now its omission from official air quality readings has been a major hurdle in solving China's air pollution crisis. After all, how can you solve a crisis when according to the readings ... there isn't one. (With those readings standing in direct contrast to the experience of any Beijinger who can stick their head out the window and cough their way through a lungful of murky, grey air.)
But the small-particulate cat is out of the bag, and air pollution has becoming an increasingly hot topic in China, no doubt in part thanks to the heavy shroud of air pollution that has been weighing down on Beijing recently. And so many Chinese cities appear set to be married to asthma and hazy skies for a very long time unless some serious measures are taken.
On Tuesday our climate and energy campaign director Sun Qingwei was interviewed by the Global Times on the topic:
"The results from the PM2.5 index are closer to the feeling of the population about the air than those from the PM10," Sun Qingwei, the director of the climate and energy research department at Greenpeace, a non-governmental organization in Beijing, told the Global Times on Tuesday.
"The PM2.5 could expose more threats to the human respiratory and blood circulation system than the PM10 due to its smaller size, and can serve as a more effective way of warning the population," Sun added.
Nevertheless, Sun stated that the PM10 standard, which is more appropriate for large spaces, can be of greater value, as small sample sizes are not always representative of the whole.
Recently revealed large differences in air pollution degrees released by the Beijing Environmental Protection Bureau (BEPB) have generated a national heated discussion over the standards adopted by the Beijing authorities. The dispute originated in discrepancies between the BEPB and the US embassy in China, who had respectively described similar levels of air pollution as "slight" and "hazardous."
"Personally, I advise authorities to involve both PM10 and PM2.5 levels in the national environment evaluation standards and thereby let citizens themselves judge which standard to follow," Sun added.
Meanwhile in the China Daily, Zhou Rong, another member from our climate and energy team, was asked about the government's plans to begin regulating PM2.5 within five years and set binding targets to reduce the fine particles between 2015 and 2020.
"As these pollutants will have a direct impact on the public health, we hope this process can be accelerated," Zhou said.
Studies on the causes of PM2.5 have been under way in China for about a decade, she said. Coal consumption and vehicle exhaust are the major causes, but in different regions their contribution to the pollution varies.
Either way, there will be no easy solutions, although Beijing's municipal government is dedicated to limiting coal consumption and vehicle ownership. It has set a goal to cap annual coal consumption at 20 million tons by 2015. Last year, Beijing burned 27.5 million tons.
"But again, air pollution is a regional problem," Zhou said. "Even if Beijing takes care of its own emissions, it still cannot escape the pollutants discharged by power plants in the neighborhood."
Read our list of "real-time apps, twitters tracking air quality levels in your Chinese city".