An unidentified man ride a bicycle in smog, in a foggy and hazy day.

For the first decades of Communist rule, China dictated a far-reaching regulation to heat homes during its winters. The Huai River Policy, in effect from 1950 through 1980, was simple: homes to the north of the namesake river received free or vastly reduced-cost coal to heat homes, while those south did not.

Half of the Asian nations may have lived more comfortably in the cold for that time – but they paid for it with shorter lives, according to a new analysis in the Proceedings of the National Academy of Sciences.

The areas just north of the river had 46 percent more particulate matter historically from their counterparts to the south of the Huai, according to the analysis.

The people to the north, they find, consequently lived 3.1 fewer years.

“The analysis suggest that the Huai River Policy, which had the laudable goal of providing indoor heat, had disastrous consequences for human health,” they write. “The analysis indicates that particulate matter exposure causes people to live substantially short and sicker lives at the concentrations present today in China and other developing countries.”

The first particulate readings were taken in the early 1980s, according to the study. The increase in air pollution from that time to the present has persisted, despite the discontinuation of the Huai River Policy, they write. The scientists compiled what they call the “most comprehensive archive of Chinese air pollution ever assembled,” and cross-referenced it with mortality records from the Chinese Centers for Disease Control and Prevention spanning the years 2004 to 2012.

The scientists controlled for health factors such as smoking and water pollution.

Their findings at the population level: if China actually brought air pollution into compliance with its own particulate matter standards, some 3.7 billion life-years would have been saved. (Even that Chinese standard of 40 micrograms of particulate matter per cubic meter is twice what the World Health Organization recommends).

“Unveiling this important information helps build the case for policies that ultimately serve to improve the lives of the Chinese people and the lives of those globally who suffer from high levels of air pollution,” said Maigeng Zhou, one of the authors, a deputy director National Center for Chronic and noncommunicable Disease Control and Prevention of the Chinese CDC.

The scientific team – from the U.S. and Israel as well as China – concluded that some 4.5 billion people in Asia and beyond are currently breathing particulate matter at levels twice the WHO level.

“Particulates are the greatest current environmental risk to human health, with the impact on life expectancy in many parts of the world similar to the effects of every man, woman and child smoking cigarettes for several decades,” said Michael Greenstone, one of the authors, from the University of Chicago, in a statement.

Previous studies have looked at the Huai River Policy. In fact, the same group of authors conducted a similar analysis in 2013 in the same journal – but this more recent look examines the health outcomes of a population approximately eight times greater.