I'm just a regional guy so I don't spend hours at a time above 360 but I do get up there and I have put some thought into the cosmic radiation thing, but a few weeks ago I was waiting out a ground stop and me and the other guy got talking about radiation. We were talking about how many times a day we get hit by radar (gnd wx, airborne wx, atc, etc) and how many more radio waves (tv, music radio, all kinds of comm, wifi, etc) are flying thru the air compared to just 100 years ago. We got to thinking and were wondering if all of this could cause an increase in the cancer rate. Haven't done any research or anything, just saw this thread and it reminded me of the conversation from a few weeks ago and thought I'd throw the topic out there.
Oh yeah another thing I heard that I didn't think I saw in here is that I heard that if we had to wear a dissimeter (I think thats what a radiation monitor is called) like the things guys in nuke places work we would only be able to work 2 to 3 factory type shifts a week before we hit our "OHSA" radiation limit. And that on a typical work week/month pilots are more than twice over the nuke factory worker limit for exposure to radiation.