Radiation exposure may involve
Radioactive contamination is the unintended contact with and retention of radioactive material, usually as a dust or liquid. Contamination may be
External contamination is that on skin or clothing, from which some can fall or be rubbed off, contaminating other people and objects. Internal contamination is unintended radioactive material within the body, which it may enter by ingestion, inhalation, or through breaks in the skin. Once in the body, radioactive material may be transported to various sites (eg, bone marrow), where it continues to emit radiation until it is removed or decays. Internal contamination is more difficult to remove. Although internal contamination with any radionuclide is possible, historically, most cases in which contamination posed a significant risk to the patient involved a relatively small number of radionuclides, such as phosphorus-32, cobalt-60, strontium-90, cesium-137, iodine-131, iodine-125, radium-226, uranium-235, uranium-238, plutonium-238, plutonium-239, polonium-210, and americium-241.
Irradiation is exposure to radiation but not radioactive material (ie, no contamination is involved). Radiation exposure can occur without the source of radiation (eg, radioactive material, x-ray machine) being in contact with the person. When the source of the radiation is removed or turned off, exposure ends. Irradiation can involve the whole body, which, if the dose is high enough, can result in systemic symptoms and radiation syndromes (see Radiation Exposure and Contamination : Acute radiation syndromes (ARS)), or a small part of the body (eg, from radiation therapy), which can result in local effects. People do not emit radiation (ie, become radioactive) following irradiation.