Geiger Counter Numbers, How Bad is Bad? Radioactivity Raw Information Overview.
also http://www.radiationnetwork.com/ . Alert is 100 CMP.
I do not know about gamma levels but I’ve researched beta levels extensively now.
30-60 CPM is the “normal” range in the U.S.
The EPA regards anything 3X background as a potential immediate health risk for emergency responders and considers 300 CPM the level at which emergency responders are required to take protective action. (I found an EPA guide for emergency responders for all kinds of “accidents”)
These levels do not cause radiation sickness but increase cancer risks and risks for other radiation-related or exacerbated conditions/illnesses