The average annual cosmic radiation dose for flight personnel was 2.19 mSv (ie, less than one CT scan) http://www.hps.org/publicinformation/ate/faqs/commercialflig...
Flight attendants 2x-5x higher cancer rates http://www.webmd.com/breast-cancer/news/20031021/flight-crew...
http://www.webmd.com/cancer/news/20100209/dry-cleaning-chemi...
The increase in cancer rates is interesting though, although if the main cause was radiation you wouldn't expect a few specific types to increase significantly and not others.
How do you figure? I don't think all of the causes of cancers are well understood. But, I know that cervical cancer is highly correlated with HPV, skin cancer is highly correlated with sun exposure, stomach cancer is highly correlated with H. Pylori, and lung cancer is highly correlated with tobacco smoking. And, for that matter, that cancers seem to have wildly different occurrence rates to begin with.
It's not even necessary to posit a 'radiation-associated cancer' category to account for differential cancer increases, as long as there are some cancers somewhere that pop up in response to things other than radiation. Existence proof: Cervical cancer, associated with a virus. We would not expect cervical cancer rates to jump to the same degree as $generic-cancer, because the radiation-caused rate of cervical cancer is only a small chunk of all cervical cancers: double it and you affect the overall rate little.
With that said, airplanes are doused in some other questionable chemicals as well - I've seen concerns expressed specifically about the breakdown of fire retardants.
To argue that cervical cancers should jump by a smaller amount than other cancers in response to radiation, showing that cervical cancers are largely caused by something other than radiation is useless -- you need to show that other cancers are largely caused by radiation.