Which cities face most, least air pollution according to new WHO data

Story highlights

  • 9 out of 10 people in the world breathe air that is highly polluted, a new report says
  • Air pollution is found in the home and outdoors
  • About 7 million people die each year because of this pollution, the WHO says

(CNN)Nine out of every 10 people on the planet breathe air that contains high levels of pollutants and kills 7 million people each year, according to a new study from the World Health Organization.

The study is an analysis of what the WHO says is the world's most comprehensive database on ambient air pollution. The organization collected the data