Radiation Limits and Units

Radiation Units & Limits

Radiation exposure levels & dosages are measured in units called roentgens, rads and rems.

• ROENTGEN – a unit of exposure in air used to measure photons or gamma rays.
• RAD [radiation absorbed dose] – measurement of energy which is absorbed by some given mass.
• REM [roentgen equivalent man] – a dose equivalent which measures the dose which is absorbed by a biological system such as a human. The measurement is rad x quality factor.
• PICOCURIE [pCi] – The basis for the Curie is the radioactivity of one gram of radium. Radium decays at a rate of about 2.2 million disintegrations per minute. A picocurie is one trillionth of a curie.  Thus, a picocurie represents 2.2 disintegrations per minute.

Where are our radiation risk?

• About 8% from outer space.
• About 55% from radon gas decay which usually moves from the ground up and migrates into homes and buildings through cracks and holes in foundations.
• The rest comes from medical procedures, fruits and nuts, cigarette smoking, etc.