1) It produces more radioactivity than all other energy sources, including Nuclear power. (A small percentage of coal is thorium, which settles around wherever you burn the coal.)
2) It takes more work to mine it than all other sources (including uranium - though it does require less processing).
3) It takes more work to ship it from it's source to the plant than all other energy types.
4) It produces more carbon pollution than all other sources. Coal is basically pure carbon plus some nasty impurities. Oil and gas are Carbon + Hydrogen + some other stuff. Carbon burns to Carbon Dioxide (or worse, monoxide). Hydrogen burns nice and clean, turning into water.
5) Coal contains trace amounts of mercury, which when burned makes it's way into the atmosphere, then rains down into the oceans. Nasty stuff. No other energy source has this problem.
6) Coal mining has some nasty problems, including black lung disease and sometimes starts underground fires we literally can NOT put out.
No sane person mines coal for energy if they have any other energy source. All others are safer and better. Burning oil, gas, or wood are all better. Nuclear is better. Tidal, wind, solar, hydro, are all better.
Coal mining should only be used after you have burned all your forests up, mined all your uraninum, pumped all your natural gas and oil, and the sun has gone out.