Southern Chinese on average have lived at least five years longer than their northern counterparts in recent decades because of the destructive health effects of pollution from the widespread use of coal in the north, according to a study released Monday by a prominent American science journal.
The study, which appears in The Proceedings of the National Academy of Sciences, was conducted by an American, an Israeli and two Chinese scholars and was based on analyses of health and pollution data collected by official Chinese sources from 1981 to 2001.
The results provide a new assessment of the enormous cost of China's environmental degradation, which in the north is partly a result of the emissions of deadly pollutants from coal-driven energy generation. The researchers project that the 500 million Chinese who live north of the Huai River will lose 2.5 billion years of life expectancy because of outdoor air pollution.
"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."
Greenstone said in a telephone interview that another surprising result of the study was that the higher mortality rates were found across all age groups.
The study is the first measuring this kind of impact that relies purely on data collected within China. Its conclusions are based on analyses of population groups living in areas north and south of the Huai River. The Chinese government has for years maintained a policy of free coal for boilers to generate winter heating north of the river, which runs parallel to and between the Yellow and Yangtze Rivers. That policy and the ubiquity of northern coal-fired factories have contributed to the vast gap between the coal pollutants emitted in north and south.
Howard Frumkin, dean of the School of Public Health at the University of Washington, said a "strong point" of the study was its basis in the "natural experiment" resulting from China's disparate coal policies. "The results are biologically plausible, and consistent with previous research," he said.
For every additional 100 micrograms of particulate matter per cubic meter above the average pollution levels in the south, the life expectancy at birth drops by three years, the researchers found. Greenstone said that estimate could be roughly applied to other developing nations where the baseline level of pollutants was high.
"This adds to the growing mountain of evidence of the heavy cost of China's pollution," said Alex L Wang, a law professor at the University of California, Los Angeles, who studies Chinese environmental policies. "Other studies have shown significant near-term harms, in the form of illness, lost work days and even risks to children beginning in utero. This study suggests that the long-term harms of coal pollution might be worse than we thought."
Wang said the new study could "help to build the case for more aggressive environmental regulation" - for example, a previous order by Chinese leaders to shut down coal-fired boilers in some areas could be widened, and faster shutdown times could be required.
The health statistics recorded through the two-decade period by Chinese officials and examined by the study's researchers showed that the 5.5-year drop in life expectancy in the north was almost entirely due to a rise in deaths attributed to cardiorespiratory diseases or related health problems.
The pollution data, also recorded by officials, indicated that the concentration of particulates north of the Huai was 184 micrograms per cubic meter higher than in the south, or 55 per cent greater.
Several recent scientific studies have revealed the toll that China's outdoor air pollution is taking on humans. This spring, new data released from the 2010 Global Burden of Disease Study revealed that such pollution contributed to 1.2 million premature deaths in 2010, or nearly 40 per cent of the global total.
Some Chinese officials have sought to quash reports that link premature deaths to pollution. According to news reports, Chinese officials excised parts of a 2007 report called "Cost of Pollution in China" that had concluded that 350,000 to 400,000 people die prematurely in China each year because of outdoor air pollution. The study was done by the World Bank with the help of the Chinese State Environmental Protection Administration, the precursor to the Ministry of Environmental Protection.
This year, many Chinese have expressed fury and frustration over the surging levels of air pollution, especially in the north, which in January had record levels of particulate matter. Pollution levels have remained high this summer, and many foreigners and middle- or upper-class Chinese with children are looking to leave the country rather than tolerate the health risks.
Greenstone said he did not have a basis for comparing pollution levels now with those during the period covered by the study, 1981 to 2001. During that time, the method of measuring particulate matter was different. Greenstone also said he did not know how pollution in northern China affected the life expectancy for people not living there for their entire lives, or for residents of northern China who made frequent or long trips to less polluted areas.
