It cannot come too soon for the choking residents of China's cities, but the country's government may finally be turning its attention to its primary and deadliest source of smog.

Tiny particulate matter known as PM2.5 - which is linked to lung disease, heart attacks and atmospheric haze - will be added to a list of air quality indicators in an upcoming revision of national standards, the Chinese media reported on Monday.

These ultra-fine particles account for more than half the weight of industrial dust in the air of northern China, according to the Jinhua Daily. Until now, their absence from the national pollution index created an absurd discrepancy between official claims of "blue sky" conditions and the reality of air so putrid and murky it could be tasted.

"At present, the public's feelings about air quality are different from the monitoring data," environment vice-minister Zhou Jian acknowledged during a speech at a recent forum. "To prevent haze, we will improve the air quality standards as soon as possible and include PM2.5."

Starting with a handful of cities, the revised index is expected to be introduced nationwide during the current five-year plan. Along with government moves earlier this year to crack down on nitrogen oxide, the new step is likely to result in tighter curbs on tailpipe and chimney emissions. It should have a major impact on health. PM2.5 - most of which comes from cars - is so small that it can enter the lungs and bloodstream. Currently, the index measures only bigger PM10 particulates from industry, which are less dangerous because they tend to get stuck in nasal passages or pass directly through the body.

Academics, environmentalists and foreign governments have long called on the government to improvfe standards.

US embassy officials noted in 2006 that China was failing to release data on PM2.5 and ozone because the levels were unsafe and politically sensitive, according to a US diplomatic cable released by Wikileaks.

China's omission has been made more glaring by real-time data on PM2.5 and ozone released via the @Beijingair twitter account by the US embassy in Beijing. Contrary to the local authorities' claims of "blue skies", it has revealed how often the pollution is "hazardous" and "crazy bad".

Overall, the authorities insist the situation is improving - a claim strengthened earlier this year by a unusually long run of clear skies - but boasts of progress have long been clouded by doubts about missing data.

This article first appeared at the Guardian

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