Radiation ecology is a multidisciplinary science that uses nuclear physics, chemistry, biology, toxicology, ecology and risk analyses to predict the effects of radioactive contaminants on humans and the environment. Such predictions require knowledge of the various radioisotopes, the particular environment in which the radioactive contaminants occur, and the ecology and physiology of the biota potentially affected. Radiation ecology deals with a continuum that starts with radioactive releases from a source term, continues through the dispersal and retention of the contaminants by environmental mechanisms, and ends with the determination of dose and health risks to exposed humans or other biota.