What's New?
•	August Newsletter
•	August ORS
•	August Journal

Upcoming Events
•	IRPA 12 19-24 October 2008
•	HPS Midyear Meeting Recent Advances in Planning and Response to Radiation Emergencies 31 January - 3 February 2009 San Antonio, Texas
•	54th Annual Meeting of the Health Physics Society 12-16 July 2009 Minneapolis, Minnesota

23 July 2008

Half-life

The time in which one-half of the activity of a particular radioactive substance is lost due to radioactive decay. Measured half-lives vary from millionths of a second to billions of years. Also called physical or radiological half-life.