Radiation in Perspective

Radiation exposure is measured in units called rem, most often expressed as millirem (mrem), which are one-thousandth of a rem. These units are used to describe how radiation affects the human body.

Everyone is exposed to small amounts of radiation every day from natural sources such as the earth, the sun, and naturally occurring radioactive materials in our environment. Medical procedures like X-rays and CT scans can also contribute to an individual’s exposure.

Health effects from radiation depend on the amount of exposure, the length of time, and how the exposure occurs. Very low levels of radiation, such as those encountered in everyday life or from properly regulated activities, have not been shown to cause immediate health effects. Higher doses received over a short period of time can cause biological effects, which is why strict limits and safety standards are in place.

Federal radiation safety standards are established and enforced by the U.S. Nuclear Regulatory Commission (NRC). These standards limit radiation exposure to:

• No more than 5,000 mrem per year for workers who are trained and monitored to work with radiation
• No more than 100 mrem per year for members of the public from licensed nuclear facilities

These limits are set well below levels known to cause harm and are designed to protect public health with a wide margin of safety.