Much of the information included on this site is about ionizing radiation. This is the type of radiation that has enough energy to change atoms in tissues. This is the radiation of chest x rays or nuclear power plant fuel. We take advantage of the properties of ionizing radiation to produce high-quality images of the inside of our body, to generate electric power, and for many manufacturing processes.
We are exposed to ionizing radiation every day. Nearly 80 percent of radiation dose we receive is from naturally occurring sources and almost all of this comes from radioactivity that is in the ground. The other 20 percent of our radiation dose comes from artificial sources—medical x rays, consumer products, industry, research, and power generation. Although the radiation dose received by an individual will vary, on average the total annual radiation dose received by each person in the United States is 0.36 rem.
Ionizing radiation is produced by unstable atoms (radioactive atoms) or by certain types of equipment (x-ray machines and CT scanners). Unstable atoms differ from stable atoms because unstable atoms have an excess of energy or weight (or both). Unstable atoms want to be stable atoms so they get rid of some of that energy or weight (or both) to try to be stable. The energy or weight emitted is ionizing radiation.