One of the great challenges of studying the health damage caused by pollution is the lack of an appropriate control group. In most places where pollution has occurred, there's no corresponding population that is unexposed, and it would be unethical to intentionally expose one group of people to pollution.
A policy to provide free coal for heating north of China's Huai river but not in the southern part of the country created such a control group, allowing researchers to study the health effects of coal pollution. Although the policy has since been abandoned, coal-burning heating systems are still present and China consumes the most coal of any nation.
Published Monday in Proceedings of the National Academy of Sciences, a new report analyzes public health data from 1981 to 2000. The authors found life expectancy to be about 5.5 years shorter in the North, where coal pollution is much more concentrated.
The authors controlled for possible confounding factors like access to care, and analyzed causes of death. The Washington Post reports:
"Concentrations of 'total suspended particulates' were about 55 percent higher in the north, thanks to the heavy coal burning. And life expectancy for those living in the north was also about 5.5 years shorter — an effect due entirely to differences in cardio-respiratory problems, which is exactly what you’d expect if pollution was the cause."
One of the study authors told the New York Times that long-term health costs may outweigh short-term economic gains:
“It highlights that in developing countries there’s a trade-off in increasing incomes today and protecting public health and environmental quality,” said the American member of the research team, Michael Greenstone, a professor of environmental economics at the Massachusetts Institute of Technology. “And it highlights the fact that the public health costs are larger than we had thought.”