Why can waste coal be harmful to the environment?

Nuclear waste is radioactive. This means that the nucleus of the atoms of the material is not stable and will throw of energy to achieve a stable state. The energy will be in one of four forms: Alpha, beta, gamma, and neutons and is often more than one of these types. This energy is called "ionizing radiation" which is radiation which will knock electrons off of the atoms it strikes. If those atoms are in molecules in cells in living tissue, enough damage will cause the cell to die. Alpha radiation is a helium nucleus, two neutrons and two protons with no electrons. The particle has a large electrical charge and high mass (comparitively) and is thus very ionizing. Beta radiation is a high energy electron. Some charge and a little mass. Gamma radiation is a photon of high energy light. No charge, no mass, lots of energy. A neutron is a neutron. No charge, some mass, can be absorbed by the nucleus of another atom and destablize it (make it radioactive).