Glow in the Dark Kid

"Mom, is it OK for me to go back to school?," asks my 11-year old wounded road warrior. We're driving back after getting his shoulder x-rayed - he broke my tail light (and his pediatrician suspects, his clavicle) after hitting my car with his new bike.

"Sure you can go back to school, why not?" "I'm radioactive now, aren't I?" "Ah....well, actually you are, but not from the x-ray!"

Slate magazine's Explainer column last week looked at the radioactivity of everyday materials in "Is Cat Litter Really Radioactive?". (The short answer is yes.) People living in the US are exposed to roughly 360 millirems of radiation a year. Most of this is from naturally occurring sources, such as cosmic radiation and radon (and cat litter). About 10% of the exposure is from your own body, which contains measurable amounts of carbon-14 and potassium-40, both are which are radioactive. Your basic banana contains about 47 μg of potassium-40. Crash Kid's x-ray probably exposed him to less than 10 mrems, about what he gets every year from flying to visit his grandparents in California. To put this all in perspective, an acute dose of 50,000 mrem could give you radiation sickness.

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Oh...the fracture is limited to the tail light!