When I saw this method of displaying different levels of radiation expsoure from different sources, I thought of Edward Tufte. He's the professor of information display, and you might check out his books if you're not aware of him.
Anyway, I like that the radiation chart from xkcd.com gives a sense of scale with boxes representing quantity, then showing that the entire collection of blue boxes from the first panel fits inside just a three of the green boxes from the second panel, and so on. It helps build our intuition about just how much radiation is contained in those last few yellow boxes. Tufte would also like that words and images are intermingled, and that the author cites the sources of his data. Great job, xkcd.