The study [PDF], published in the Proceeding of the National Academy of
The policy provided free coal for boilers to residents in cities North of the Huai River during the winter months between 1950 and 1980. Coal ash from the boilers led to an increased incidence of death from heart and lung problems due to pollution.
The researchers found that total suspended particulates are 55% higher in the north. Poor air quality is "causing 500 million residents of Northern China to lose more than 2.5 billion life years of life expectancy," the authors write.