World's 10 cities with worst air quality are in India and Pakistan

Much is being made of the air-pollution problem in Vancouver.

But data from the World Health Organization shows that India and Pakistan are home to the 10 cities with the highest ratio of fine particulates of 2.5 microns or less in width.

Particulates of this size tend to lodge deeper in the lungs an bloodstream, leading to heart attacks and early death.

Delhi ranks first with 153 micrograms of tiny particulates per cubic metre of air. It's followed by the capital of the Indian state of Bihar, Patna, at 149.

Next are the Indian cities of Gwalior and Raipur at 144 and 134, respectively, followed by three cities in Pakistan: Karachi (117), Peshawar (111), and Rawalpindi (107).

Ranking eighth and ninth are the Indian cities of Khormabad (102) and Ahmedabad (100). Tying for tenth are Lucknow (96) and Firozabad (96), which are both in India.