Greenhouse Gas Emission
Coal Mining is one of the largest producers of CO2 which is often claimed responsible for "Global Warming"
Worker Death
Each year many thousands of miners die in mining accidents
Destruction of Habitat
All above ground mines are required to remove the trees from the area and to misplace all the animals in the area
Human Displacement
For many mines especially in developing nations, like China, people are removed to get to the coal. many people find this unethical and bad for everybody.
http://www.greenworldinvestor.com/2011/04/11/coal-advantages-and-disadvantages-pros-of-coal-winning-despite-dangerous-cons/