I wouldn't worry about radiation from altitude, more likely to be a problem simply going to the airport. All those aircraft and occasionally some forget to turn off the radar plus the airports weather radar, trust me, you'd be baked long before you got in the air.
Just joking, I have heard of very little problems, I know it has been looked into but as of yet they have found nothing. If you were cruising at 60,000 then you might have a concern, but in the mid 30's, which is where most airliners fly, you'll be find. Making an issue out of nothing, get more radiation from all the mircowaves, security systems, cell phones, sun, etc... while on the ground