REUTERS/Stringer
Citizens walk across a bridge in China, their line of sight extremely short due to the thick smog.
Air pollution poses a serious threat to human health, especially in developing countries like China where the quality of air is particularly bad.
A recent study from UC Berkeley estimated that air pollution contributes to 1.6 million deaths in China per year - that's about 17% of the country's population!
Moreover, experts calculate that air pollution kills more people worldwide than AIDS, malaria, breast cancer, or tuberculosis.
For a broader perspective on the dangers of air pollution, the producers at Column Five - an agency that specializes in informative graphics - made this awesome graphic on the major causes of air pollution in China and globally, how to measure air quality, and what it would take to clean up air in some of the dirtiest places on Earth:
