Free coal was the case in part of northern China 1950-1980, for household heating. Health consequences discussed in PNAS, here is the BBC version BBC News - China free-coal policy in the north 'cut lifespans' Apparently not the ideal household fuel.
Wood, maybe dung. Some probably already using coal. China was the first nation to drill for natural gas, using bamboo pipes for distribution. So maybe that.
lol. Do we really need to study this? Its as if companies gave free booze and cigarettes at work and encouraged drinking, then someone did a study to see if drunk driving accidents and cancer rates rose during this period. Its rather obvious, but the results don't really help prevent problems today. Yes but it wasn't all free, that free part made people use more. I mean if the government wants me to burn it, why not burn lots of it. That smoke won't really hurt me.
