Since the Fukushima nuclear disaster, you've probably heard me and other people talk about the radiation exposure we experience in everyday life. All humans, throughout history, have been exposed to background radiation produced constantly by the natural environment. Then there's added exposures from modern sources: X-rays and medical scans, living near power plants (both coal and nuclear, and the coal is actually worse), and flying in airplanes.
That last source of exposure works because the higher you get, the less you can rely upon Earth's atmosphere to shield you from radiation in space. It's the same reason why there's an increase in radiation exposure associated with climbing a mountain. All of these exposures are small. Small enough that most people don't need to worry about them. (For instance, a pregnant woman can safely take an airplane trip. You'd have to be a pregnant flight attendant, regularly working long-haul flights, before the exposures would start adding up to a quantifiable risk.)
But because we use these small-dose numbers to talk about relative risk and when radiation should and shouldn't scare us, it's interesting to know where they're coming from ... and how accurate they are. That's why I was interested in something weird noticed by Ellen McManis. She operates a research nuclear reactor at Reed College in Portland, Oregon, and like many of us, she's curious about how much radiation people are actually being exposed to as a part of everyday life. Unlike us, however, McManis actually has access to things like dosimeters. With the help of her colleague, Reuven Lazarus, she recently took one on a cross-country plane flight—from Portland to DC, with a layover in Chicago. To her surprise, she found that the dose her dosimeter registered was actually a lot lower than the dose she'd been expecting.