Radiation is energy in motion. Radioactive materials are naturally present all around us—in the air we breathe, the food we eat, our homes, and even within our own bodies. Exposure to radiation from these natural sources is known as background radiation. The type of radiation we are most concerned with is called ionizing radiation—a form of energy released by radioactive materials. Ionizing radiation has enough energy to penetrate living tissue and cause physical and chemical changes within the body. In addition to natural sources, ionizing radiation also comes from man-made sources such as:
- Medical treatments and diagnostic tools (e.g., X-rays)
- Consumer electronics (e.g., older TV sets)
- Nuclear power plants
Radiation exposure is measured in units called millirems. On average, a person receives about 620 millirems per year from both background and man-made sources. Half of this radiation comes from natural sources, including radon in the air, cosmic rays, and the Earth itself. The other half comes from man-made sources, including medical procedures, as well as commercial and industrial sources.