Unintended Consequences

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Science  26 Jul 2013:
Vol. 341, Issue 6144, pp. 319
DOI: 10.1126/science.341.6144.319-d

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Half a century ago, in what probably seemed like an entirely beneficent central planning program, coal for winter heating was provided free of charge to homes north of the River Huai in China for several decades. Burning this coal released particulate matter that contributed to a decline in air quality. Through a painstaking accumulation of data on suspended particulates in the 1980s and 1990s, coupled to a regression discontinuity design—in essence, assuming that unobservable parameters change smoothly from one side of the river to the other and checking to ascertain whether observable parameters obey this assumption—Chen et al. are able to demonstrate that the concentration of particulates shifts abruptly from about 400 µg/m3 on the south side to 600 mg/m3 on the north bank. What is rather worrisome is that they also find that life expectancy drops by about 5 years when crossing the river from south to north. The higher mortality rate is due to an increase in cardiorespiratory disease, such as stroke and lung cancer, and not to other cancers.

Proc. Natl. Acad. Sci. U.S.A. 110, 10.1073/pnas.1300018110 (2013).

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