In November 2012, when the city was in the throes of its worst smog spell in recent years, PM2.5 levels were consistently over 500 mg/cu m over several places.
“Beijing undertook several measures to control its air pollution levels during the Beijing Olympics in 2008 but the city is still prone to smog. More recently, it has decided to implement a lottery system for private cars which it hopes will keep a check on the rising number of vehicles,” said Anumita Roychowdhury, associate director at the Centre for Science and Environment.