Delhi is world’s most polluted city and Mumbai is fourth, according to air quality data compiled by the World Health Organisation (WHO)  for megacities with a population of 14 million or more.

Globally, air pollution levels remain dangerously high in many parts of the world.

New data from WHO shows that 9 out of 10 people breathe air containing high levels of pollutants. Updated estimations reveal an alarming death toll of 7 million people every year caused by ambient (outdoor) and household air pollution.

In general, ambient air pollution levels are lowest in high-income countries, particularly in Europe, the Americas and the Western Pacific.In cities of high-income countries in Europe, air pollution has been shown to lower average life expectancy by anywhere between 2 and 24 months, depending on pollution levels (source).