Sulfur is a big one. https://en.m.wikipedia.org/wiki/Coal https://en.m.wikipedia.org/wiki/Coal Leading to, for example, acid rain. Also just a guess, coal is

Sulfur is a big one. https://en.m.wikipedia.org/wiki/Coal https://en.m.wikipedia.org/wiki/Coal Leading to, for example, acid rain. Also just a guess, coal is a finer particulate matter than wood, I think that might give more particles off. Wood dust, nope, coal dust? Hell no. Also radioactive!