Beijing recently issued its first pollution 'red alert', but can it find a more permanent solution to the smog which blights much of China?
A policy to restrict the number of cars on Delhi's roads reduces congestion, but makes no noticeable difference to air pollution levels.
How do scientists assess the scale of dirty air across the UK and just how dangerous is the air that we breathe?
The European Commission says the UK has two months to address repeated breaches of air pollutants.
Tiny particles of pollution have been discovered inside samples of brain tissue, according to new research.