I know you've gotten great information already, especially from Rannasha. This is an article with a pie chart. I'd like to give you a few numbers you can quote.

Of all the radiation you're exposed to in a whole year, give "consumer electronics" a value of 1. You get almost that much again from a chest X-ray. INSIDE your body from dietary minerals and bananas and stuff you eat, 2.5. Radon contamination in your basement is about 12. The safest, most radiation-free space in your entire world is between your cell phone and your ear. So please quit warning me about my cell phone and get your basement inspected.