Cities in Iran, India, Pakistan and Mongolia are 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.
The Iranian city of Ahvaz had the distinction of the highest measured level of airborne particles smaller than 10 micrometres, according to the UN’s World Health Organisation (WHO) survey.
Outdoor air pollution causes an estimated 1.34 million premature deaths a year, said WHO.
Cities in Pakistan and India, such as Quetta and Kanpur, as well as Botswana’s capital, Gaborone, also ranked high on the pollution scale.
WHO said the reasons for the high levels varied but that often rapid industrialisation and the use of poor quality fuels for transport and electricity generation are to blame.
At the other end of the list are cities in Canada and the US, which benefit from lower population density, favourable climates and stricter air pollution regulation.