The combined photo taken at Jingshan Park shows the scene of southern Beijing on July 02, 2013 (top) and on June 28, 2013 (bottom). A heavy rainfall and strong wind hit Beijing at the night of July 01, 2013, eliminating the haze enveloping China's capital and bringing a clear day to it on July 02. Photo: Xinhua

Air pollution cuts life expectancy in China's north by an average of 5.5 years with diseases such as lung cancer, heart disease and strokes at higher rates than elsewhere, according to a new study.

A paper [pdf] produced by Yuyu Chena, Avraham Ebensteinb, Michael Greenstone, and Hongbin Lie, respectively of Guanghua School of Management, Peking University, Beijing; Department of Economics, Hebrew University of Jerusalem; Department of Economics, Massachusetts Institute of Technology and China Data Center and Department of Economics, School of Economics and Management, Tsinghua University, Beijing, and published this week in PNAS (Proceedings of the National Academy of Sciences of the United States of America) a leading journal, the authors  report on their research on the health consequences of  "extraordinary pollution levels by exploiting a seemingly arbitrary Chinese policy that produced dramatic differences in air quality within China. During the 1950–1980 period of central planning, the Chinese government established free winter heating of homes and offices via the provision of free coal for fuel boilers as a basic right."

The researchers say the combustion of coal in boilers is associated with the release of air pollutants, and in particular emission of particulate matter that can be extremely harmful to human health. Due to budgetary limitations, however, this right was only extended to areas located in North China, which is defined by the line formed by the Huai River and Qinling Mountain range. "Even today, the long-lived heating systems continue to make indoor heating much more common in the north."

They estimate that the 500m residents of Northern China during the 1990s experienced a loss of more than 2.5bn life years owing to the Huai River policy.

Last April, The New York Times reported that outdoor air pollution contributed to 1.2m premature deaths in China in 2010, almost 40% of the global total, according to a new summary of data from a scientific study on leading causes of death worldwide.

China’s toll from pollution was the loss of 25m healthy years of life from the population.

The data on which the analysis was based was first presented in the 2010 Global Burden of Disease Study, which was published in December in The Lancet, a British medical journal. The authors separated the numbers for specific countries. The China statistics were offered at a forum in Beijing last April.

“We have been rolling out the India- and China-specific numbers, as they speak more directly to national leaders than regional numbers,” said Robert O’Keefe, the vice president of the Health Effects Institute, a research organization that is helping to present the study. The organization is partly financed by the United States Environmental Protection Agency and the global motor vehicle industry.

What the researchers called “ambient particulate matter pollution” was the fourth-leading risk factor for deaths in China in 2010, behind dietary risks, high blood pressure and smoking. Air pollution ranked seventh on the worldwide list of risk factors, contributing to 3.2 million deaths in 2010.

By comparison with China, India, which also has densely populated cities grappling with similar levels of pollution, had 620,000 premature deaths in 2010 because of outdoor air pollution, the study found. That was deemed to be the sixth most common killer in South Asia.

When conditions are correct, Asian-born pollutants can be projected into the lower-free troposphere and catch a ride on the jet stream, sometimes arriving in California in as little as 4 days. The FT's Christopher Booker reports from San Francisco on how the state is working to understand just how large the foreign contribution might be:

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