Unfortunately, we don't have the data. Yep, it's non linear, but all of our data is basically on two ends of the spectrum. Low amounts of radiation on one end,

Unfortunately, we don't have the data. Yep, it's non linear, but all of our data is basically on two ends of the spectrum. Low amounts of radiation on one end, accumulated from natural sources or working at nuclear plants, and high amounts of radiation on the other, accumulated from survivors of Hiroshima, Cherynobyl, and some nuclear accidents. So, given those data points, with clusters on two ends of this spectrum you're stuck with interpolation. Ideally, we'd like a good, predictive, biological based model that explicitly showed how you go from biological damage to cancer or death. We don't have that (though there are people researching it), so we go with statistical techniques. This results in basically 3 different proposed models. http://en.wikipedia.org/wiki/Linear_no-threshold_model http://en.wikipedia.org/wiki/Linear_no-threshold_model The Linear No Threshold Model: Draw a line between the two regions. Bam! Done. This is clearly wrong for very large doses, but is used mostly to try and estimate the effect of a small change in radiation exposure to predict increase in cancer incidence. This is very important for public policy. Of course, this makes all these models politically contested. http://en.wikipedia.org/wiki/Threshold_model http://en.wikipedia.org/wiki/Threshold_model Threshold Model This model predicts that small amounts of radiation has zero effect on cancer incidence. According to this model, going to higher altitude, or taking a plane flight, won't increase your risk of cancer. http://en.wikipedia.org/wiki/Radiation_hormesis http://en.wikipedia.org/wiki/Radiation_hormesis Radiation Hormesis A little radiation is good for you! The biological argument is that your body gets used to dealing with damage from radiation. Don't tax it too hard and you'll be stronger. So take a plane trip, and enjoy the X-ray scans!