Exposure to fine-particle outdoor pollution remains persistently high in most places. More than half of the world's population lives in areas that do not even meet WHO's least-stringent air quality target.

Ozone pollution has been slowly but steadily increasing over the past decade. This pollution is accelerated by — and contributes to — climate change.

Nearly half of all people are exposed to household air pollution from cooking with solid fuels. However, this number is dropping as more homes get access to cleaner energy sources.