Flight crews are exposed to tremendous amounts of radiation and suffer much higher cancer numbers as a result. One crew member I am aware of carried a dosimeter with him on flights. He was disciplined and told not to take unauthorized equipment in the cockpit when he tried to discuss the results.
“ Air travel increases your exposure to cosmic radiation. A return transatlantic flight exposes you to around 0.1 mSv or around five times the radiation of a chest X-ray.”
“ Aircrew (consisting of flight attendants, pilots, or flight engineers/navigators) are exposed to cosmic ionizing radiation (CIR) at flight altitude, which originates from solar activity and galactic sources. These exposures accumulate over time and are considerably higher for aircrew compared to the general population, and even higher compared to U.S. radiation workers.”

Ask a doctor how he would feel about a pregnant crewmember getting the equivalent of 20 chest X-rays a month. It’s kind of the dirty little secret no one wants discussed.