BACKGROUND: Airline pilots and flight crews may be exposed to higher radiation levels and therefore greater risk of developing cancer. They and frequent fliers can be subjected to a considerable amount of radiation in flight. The type of radiation is generally classified as cosmic radiation and can include subatomic particles and gamma and X-rays, from the sun and other sources in space. The atmosphere around equatorial regions tends to be thick and acts as a radiation shield. This layer is thinner near the poles, and therefore courses that carry planes over polar regions are the most susceptible to cosmic radiation. Higher cruising altitudes reduce atmospheric protection and people experience more exposure to radiation.
HOW RADIATION AFFECTS CELLS: Most of us are aware that the sun's ultraviolet (UV) radiation can damage surface skin cells, even leading to skin cancers, but at high energies it can become ionizing radiation. Ions are electrically charged atoms, a byproduct of a high-energy light ray (X-rays or gamma rays) knocking electrons off of atoms. The resulting free electrons then collide with other atoms to create even more ions. This is dangerous because an ion's electrical charge can lead to unnatural chemical reactions inside cells. It can break DNA chains, causing the cell to either die or develop a mutation and become cancerous, which can then spread. And if the mutation occurs in a sperm or egg, the result can be birth defects, which is why pregnant women should never be subjected to X-rays.