South Asia's air pollution woes

37 of the 40 most polluted cities are in South Asia. PM2.5 levels in Delhi, Kathmandu, Lahore, and Dhaka are up to 20 times higher than levels the WHO calls 'healthy'. What are the reasons for this, and what are the solutions? Experts track it down to a spurt in economic activity and industrialization that is tripping over itself. The World Bank has called for a coordinated approach among South Asian nations to defeat the malaise and the very real threat it poses.