GENEVA: Cities in Iran, India, Pakistan and the capital of Mongolia rank among the worst on the planet for air pollution, while those in the US and Canada are among the best, according to the first global survey, released on Monday by the World Health Organisation.

The southwest Iranian city of Ahvaz walked away with the unfortunate distinction of having the highest measured level of airborne particles smaller than 10 micrometers.

Cities in Pakistan and India, such as Quetta and Kanpur, as well as Botswana's capital Gaborone, also ranked high on the pollution scale.—AP