Useful chart for comparison
http://www.informationisbeautiful.net/visualizations/radiation-dosage-ch...
This is a great chart although I think it fails to address the difference between internal and external doses, which we need to get from other sources BUT this gives a really good breakdown in a simple illustration.
Obviously if you drink irradiated milk and water the radiation can concentrate in the body and provide a much more damaging effect while it is pasing through the system or is bioaccumulated there.
Posted by Bill

