The world's most polluted capital city, New Delhi, has an annual average of 113.5.

Russian authorities prohibited sensors in Moscow while officials in Egypt's famously polluted capital city Cairo arrested students taking part in the project.

Over the past few years, at least two dozen of Aminagar's 550-odd villagers have left for India's polluted capital to find work.

They range from green, low-cost housing in Mongolia's polluted capital and a methane-fuelled rapid-transit bus system in Karachi to restoring climate-threatened ecosystems in Namibia.

Vox successfully lobbied to remove the former Madrid mayor's signature programme - a low-emissions zone in the exceptionally polluted capital - from the governing pact.