Air quality issue for developing nations
13 February 2016 Last updated at 05:37 GMT
More than 5.5 million people worldwide are dying prematurely every year as a result of air pollution, according to new research.
Most of these deaths are occurring in the rapidly developing economies of China and India.
The main culprit is the emission of small particles from power plants, factories, vehicle exhausts and from the burning of coal and wood.
The data was compiled as part of the Global Burden of Disease Project.
Michael Brauer, from the University of British Columbia in Canada, explained the issues to our correspondent Jonathan Amos.