Radiation: Dose and Risk

So, I'm in process on putting together a post that will, hopefully, add some context to the concept of radiation exposure and relative risk. It's coming together slowly because (shocker) many of America's nuclear energy and radiation scientists are kind of busy right now, and answering my questions isn't the first thing on their to-do lists. But, in the meantime, I did want to share one really interesting tidbit that I picked up from an email exchange with Kathryn A. Higley, PhD, head of Oregon State University's Dept. of Nuclear Engineering & Radiation Health Physics.

One of the key things I'm trying to better understand, myself, right now, is the connection between radiation dose experienced, and risk of cancer later. It turns out, this is a little weird—both because of how the science works, and because of the somewhat arbitrary cutoff lines we've set for concepts like "annual dose".

Dr. Higley doesn't have good data on specific radiation doses humans are being exposed to at the Fukushima Daiichi power plant—partially, because that information keeps changing as the situation changes. But she told me that one plant worker received a 10 rem dose—twice the annual occupational dose, i.e. twice what regulators have deemed safe for someone who works in a nuclear power plant to receive every year. By contrast, somebody who gets a CAT scan is exposed to a dose of 1-2 rem.

But what kind of risk does that actually translate into? The outcome is a lot less scary sounding than I'd expected. "We assume (and it is subject to some strenuous scientific debate) that any incremental exposure to radiation can increase your risk," Dr. Higley wrote to me. "But the radiation worker that was reported to get a dose of 10 rem would only see his/her risk go up by .5 – 1%."

That is: Twice the annual safe dose of radiation equals a 1% increase in a person's lifetime risk of developing cancer. That's not trivial. But it's also not something I'd panic over, either. In fact, I think this is what makes debates over nuclear energy so damn complicated. Reasonable people can look at the increased risks, and come to completely different conclusions about whether or not those risks are acceptable.