An estimated 4.5 billion people are currently exposed to particulate matter (PM) levels at least twice the concentration that the WHO considers safe. Existing evidence linking health to air pollution is largely based on populations exposed to only modest levels of PM and almost entirely composed of observational studies, which are likely to confound air pollution with other unobserved determinants of health. This study uses quasiexperimental variation in particulate matter smaller than 10 μm (PM10) generated by an arbitrary Chinese policy to find that a 10-μg/m3 increase in PM10 reduces life expectancy by 0.64 years. The estimates imply that bringing all of China into compliance with its Class I standards for PM10 would save 3.7 billion life-years.

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