New evidence on the impact of sustained exposure to air pollution on life expectancy from China’s Huai River Policy
. Proceedings of the National Academy of Sciences 2017
, 10384–10389. Publisher's VersionAbstract
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.This paper finds that a 10-μg/m3 increase in airborne particulate matter [particulate matter smaller than 10 μm (PM10)] reduces life expectancy by 0.64 years (95% confidence interval = 0.21–1.07). This estimate is derived from quasiexperimental variation in PM10 generated by China’s Huai River Policy, which provides free or heavily subsidized coal for indoor heating during the winter to cities north of the Huai River but not to those to the south. The findings are derived from a regression discontinuity design based on distance from the Huai River, and they are robust to using parametric and nonparametric estimation methods, different kernel types and bandwidth sizes, and adjustment for a rich set of demographic and behavioral covariates. Furthermore, the shorter lifespans are almost entirely caused by elevated rates of cardiorespiratory mortality, suggesting that PM10 is the causal factor. The estimates imply that bringing all of China into compliance with its Class I standards for PM10 would save 3.7 billion life-years.