A new study has found shocking evidence of China's air pollution having a severe impact on human health and life expectancy.

Air pollution in China has resulted in reduction of life expectancy by 5.5 years, according to a new study by professors from Massachusetts Institute of Technology in the United States, Tsinghua University and Peking University in Beijing and the Hebrew University of Jerusalem. The results of the study are based on decades of pollution data from across China. The increase in toxic smog in northern China has become a national concern after Beijing recorded the highest levels of pollution in January.

According to previous analysis, air pollution in the north of China caused a loss of 2.5 billion years of collective human life expectancy in the 1990s. The new study shows for the first time the impact of long-term air pollution on human health and life expectancy, says Li Hongbin, economics professor at Tsinghua University and a co-author of the study. It provides sufficient data for the government to take serious steps toward solving the pollution issue, he adds.

The study also notes that air pollution is not only the cause of a reduction in life expectancy but also gives rise to deadly diseases including heart attacks and strokes. Elevated levels of pollution have led Beijing to impose new environmental laws and regulations but they have had little impact on repairing the damage of decades.

China's Free Coal policy is the major cause of air pollution in the north of Huai River compared to the south. The government supplies free coal for heating in winter. Researchers found an increase of 100 micrograms of total particulate matter per cubic meter, a common measure of air pollution, by comparing pollution data from 1981-2000 and health data from 1991-2000. The increase in air pollution is responsible for a 3-year reduction in life expectancy. The difference between the north and the south of the river is 185 micrograms per cubic meter, says the study.

"Part of the novelty of this study is that this was conducted with data on actual pollution measurements in China, and actual health and life expectancy in China. It is not an extrapolation," said Michael Greenstone, a professor of environmental economics at MIT and a co-author of the study, according to Financial Times.

The study is published in the journal Proceedings of the National Academy of Sciences.