An international study has confirmed the all too obvious - that the air pollution wrought by the excessive coal burning in China's north has affected the life expectancy of the people there, reducing it by as much as five years.

The new study, which worked on decades of pollution data from across China, said that the that air pollution in the north was a major factor to the loss of 2.5 billion years of human life expectancy during the 1990s.

"This is the first time anyone has got the data to show how severe long-term pollution affects human health, both in terms of life expectancy and the types of disease," Li Hongbin, an economics professor at Tsinghua University and a co-author of the study, said. "It shows how high the cost of pollution is in terms of human life - and that it is worth it for the government to spend more money to solve the pollution issue, even if we have to sacrifice growth."

What added more injury was that in China's north, free coal is highly accessible, especially during the winter. The results though were catastrophic.

Life of People in China’s North Gets 5 Years Off Expectancy All Due to Coal Burning Air Pollution

The region of about 500 million people, which has an air pollution 55 per cent higher than in the south, likewise had higher rates of heart and lung disease because of the free coal program that was in operation till 1980.

"Life expectancies are about 5.5. years lower in the north owing to an increased incidence of cardio-respiratory mortality," the study, published in the Proceedings of the National Academy of Sciences, said.

"The analysis suggests that the Huai River policy, which had the laudable goal of providing indoor heat, had disastrous consequences for health."

The new study was co-authored by professors from Massachusetts Institute of Technology in the US, Tsinghua University and Peking University in Beijing, and the Hebrew University of Jerusalem.

Michael Greenstone, a professor of environmental economics at the Massachusetts Institute of Technology, said the study likewise highlighted that "in developing countries there's a trade-off in increasing incomes today and protecting public health and environmental quality."

"And it highlights the fact that the public health costs are larger than we had thought."

About 2 million people die annually from air pollution, according to the World Health Organization. Most of these deaths are found in developing countries with the most polluted cities such as Karachi, New Delhi, Kathmandu, Beijing, Lima and Cairo.