These two terms are often confused. Exposure to radiation other than background is usually of short duration and occurs after entering an area in which there is a radiation source. While in the area, radiation exposure occurs. After leaving the area, the exposure ceases. Any biologic changes resulting from the radiation are determined by the amount of exposure received. The patient does not become radioactive. Receiving a chest X-ray is an example of exposure.
Contamination results when a radioactive material is either on the surface (external contamination) of a patient, or has somehow entered into the body (internal contamination). External contamination is often easily removed by removing the contaminated clothing and washing the affected area with soap and water or other mild cleansing solution. Internal contamination is treated using techniques that are outlined in the section on decontamination. Harsh detergents and abrasive materials should be avoided in external decontamination. These agents may break the integrity of the skin and convert an easily managed external contamination to a more difficult to treat case of internal contamination.