What are the biological effects of radiation exposure?
Radiation exposure causes direct and indirect damage to biological tissues at the cellular level  . If the energy of a radiation particle is absorbed by the nucleus of a cell, it has the potential to damage the cell’s DNA or an organelle critical for survival. This is considered a direct effect. If the cellular injury is severe enough or interferes with mitosis, the cell will be marked for apoptosis. Alternatively, if the water within the cell absorbs the energy of the radiation particle, reactive oxygen species (also known as free radicals) can be produced via the radiolysis of water. This is considered an indirect effect and can result in damage to the DNA of the originally radiated cell or to other (even distant) cells in the body. Cells that are more mitotically active (i.e., dividing more often) are more sensitive to direct damage from radiation. DNA damage can occur in the form of single-strand or double-strand breaks, single-base alterations, or abnormal cross-linking between DNA strands or between DNA strands and proteins. If the damage is not severe enough to result in cell death, it can be propagated to subsequent generations of cells.