Sky blue

With booming industries, Beijing finds it difficult to control SO2 and particulate matter. NO2 and toxic hydrocarbons add to its problems. After seven years of controls, SO2 and CO are down by nearly 25 per cent, but NOx is down by 17 per cent and PM10 levels marginally. Inhalable particles are very high on days that do not qualify as blue sky days.

Scientists from Peking University released data in 2006 to show that levels of the tiniest and most harmful particles