Don't get caught up in paranoid delusions about "nuclear" hazards...
Regarding radioactive materials, the shipping requirements are very stringent. Only low level stuff is normally shipped commercially, higher-level stuff is handled by specialty couriers or the government.
The radiation measureable at the surface of the container would be negligible, and only the guy handling it would even be exposed to that. The radiation level drops per the radius cubed, so a pilot sitting even ten feet away would be exposed to 1/1,000 the level at one foot from the conatainer.
You would not be exposed to any contamination unless the container ruptured.
Regarding occupational exposure, I have a close relative who is health physicist, and we ran the numbers for exposure to cosmic and solar radiation at altitude. There is a very, very slight increase in cancer risk based on the increase in radiation exposure. We used a long-haul guy as an example, a regional or 135 pilot flying lower altitudes and up and down a lot would experience negligible risk. I try to offset what little risk there is with anti-oxidants.
Actually I think the real health risks we confront are caused by crycadian disruptions, dehydration, vibration (prop planes), chemical exposure (jet A)and poor diet. Drink lots of water and take your vitamins.
Airline pilots, boxers, and jack-hammer operators all have an unusually high incidence of ALS (Lou Gherig's Disease). The only obvious common factor here is vibration/impact. Remember most of the old guys who worked long to become a statistic had significant prop time. I doubt jets don't contribute to this problem. I'd like to see a study on props vs. jets.