The first thing I thought of were the reports of all the heavy metals that are found in coal smoke (and therefore spread over the land and sea).
This is from the wikipedia article on Smoke. There are several elements there that I would be concerned about, but how they would be bound up in the non oxidized coal, I have no idea.
Smoke emissions may contain characteristic trace elements. Vanadium is present in emissions from oil fired power plants and refineries; oil plants also emit some nickel. Coal combustion produces emissions containing aluminium, arsenic, chromium, cobalt, copper, iron, mercury, selenium, and uranium.
I personally would err on the side of caution.