food for thought
The University of Iceland (Dr Rasmussen I think) published some leading peer reviewed papers in the late 1990s and early 2000s. There was some evidence that cosmic radiation on long haul flights presented a higher risk. A Swesish study found higher breast cancer rates (than normal background levels) in Swedish female aircrew.
The Concorde flight crews had their fare share of acute myeloid leukemias and cancers- notably prostate. Military cancer rates are higher too- both these groups operate at FL40 -55 +.
The higher you go, the bigger the risk - short duration or long.
Lufthansa implemented a protocol on flight and cabin crews to reduce long haul exposure by mixing and matching long haul crews with short haul work.
The experts I know are predicting long term cosmic radiation effects on crews after 10 -15 years of the ultra-long haul A3340/380 fligths ie SIN-JFK.
But then the radiation levels on the ground in Cornwall are pretty high chaps...And frankly you are more at risk from pesticide residues in your cheap and nasty, clean and bright, supermarket food and the parabens in mens and womens toileteries - especially underarm deoderants...
Flying is safer ...