millirems
rem = rad factor where factor is a number greater than or equal to 1 that takes into account the type of radioactive emission and sometimes the type of tissue being exposed. For beta particles, the factor equals 1. For alpha particles striking most tissues, the factor is 10, but for eye tissue the factor is 30. Most radioactive emissions that people are exposed to are on the order of a few dozen millirems mrem or less; a medical X-ray is about 20 mrem. A sievert Sv is a related unit and is defined as 100 rem. What is a persons annual exposure to radioactivity and radiation? Table 15.3 "Average Annual Radiation Exposure Approximate " lists the sources and annual amounts of radiation exposure. It may surprise you to learn that fully 82% of the radioactivity and radiation exposure we receive is from natural sources sources we cannot avoid. Fully 10% of the exposure comes from our own bodieslargely from carbon-14 and potassium-40. Table 15.3 Average Annual Radiation Exposure Approximate .