In their paper, the researchers address some other potential caveats. For instance, extensive mobility in a population might make it hard to draw cause-and-effect conclusions about the health effects of regional pollution. But significantly, in China, Greenstone says, "In this period, migration was quite limited. If someone is in one place, the odds are high they [had always] lived there, and they would have been exposed to the pollution there."
Moreover, Greenstone adds, "There are no other policies that are different north or south of the river, so far as we could tell." For that matter, other kinds of air pollution, such as sulfur dioxide and nitrous oxides, are spread similarly north and south of the river. Therefore, it appears that exposure to particulates is the specific cause of reduced life expectancy north of the Huai River.
In addition to Greenstone, the paper has three other co-first authors: Yuyu Chen, of the Guanghua School of Management at Peking University; Avraham Ebenstein, of Hebrew University of Jerusalem; and Hongbin Li, of the School of Economics and Management at Tsinghua University. The research project received funding from the Robert Wood Johnson Foundation and the National Natural Science Foundation of China.
Another reason to limit emissions
Greenstone notes that the researchers were not sure what result they would find when conducting their study. Still, he says of the finding, "I was surprised by the magnitude, both in terms of [the quantity of] particulates, and in terms of human health."
Greenstone says he hopes the finding will have a policy impact not only in China, but also in other rapidly growing countries that are increasing their consu
|Contact: Vicki Ekstrom|
Massachusetts Institute of Technology