"Everyone understands it's unpleasant to be in a polluted place," Greenstone says. "But to be able to say with some precision what the health costs are, and what the loss of life expectancy is, puts a finer point on the importance of finding policies that balance growth with environmental quality."
A river runs through it
The research stems from a policy China implemented during its era of central planning, prior to 1980. The Chinese government provided free coal for fuel boilers for all people living north of the Huai River, which has long been used as a rough dividing line between north and south in China.
The free-coal policy means people in the north stay warm in winter but at the cost of notably worse environmental conditions. Using data covering an unusually long timespan from 1981 through 2000 the researchers found that air pollution, as measured by total suspended particulates, was about 55 percent higher north of the river than south of it, for a difference of around 184 micrograms of particulate matter per cubic meter.
Linking the Chinese pollution data to mortality statistics from 1991 to 2000, the researchers found a sharp difference in mortality rates on either side of the border formed by the Huai River. They also found the variation to be attributable to cardiorespiratory illness, and not to other causes of death.
"It's not that the Chinese government set out to cause this," Greenstone says. "This was the unintended consequence of a policy that must have appeared quite sensible." He notes that China has not generally required installation of equipment to abate air pollution from coal use in homes.
Nonetheless, he observes, by seizing on the policy's arbitrary use of the Huai River as a boundary, the researchers could approximate a scientific experiment.
"We will never, thank goodness, have a randomized controlled trial where we expos
|Contact: Vicki Ekstrom|
Massachusetts Institute of Technology