A soldier and visitor look at the Wangjialing coal mine in northern China's Shanxi province. - 

A Chinese government policy that encourages the burning of coal for heat in its northern regions may be cutting life expectancy by an average of more than five years for millions of people, according to a new study from MIT, Peking University and several other research institutions.

The BBC's John Sudworth joins Marketplace Morning Report host David Brancaccio from Beijing to explain.