Yet another source of excellent information on radiation.

I ran across the following website while searching for the effects of weather on background radiation. This site has a large amount of information!

Welcome to the Health Physics Society

Find information and answers to your questions about radiation and radiation safety/protection. For many years radiation has been beneficial to human beings for medical diagnosis and therapy, scientific research, and generating electrical power. However, when used in unsafe ways, radiation can harm people. Care must be taken to properly use radiation and to minimize unnecessary radiation exposures. The health physicist's job is to manage the beneficial use of radiation.

Here is the link to HPS. Enjoy!
http://hps.org

HPS FAQ's. Here:
http://hps.org/publicinformation/ate/cat10.html

Health Physics also has a app for iPhone on the iTunes App Store. Search for "Health Physics"
The app provides free access to many HPS Journals.