Ultra-Violet & Cosmic Radiation

Copyright Max Wettstein, Not Medical Advice

    Ultra-Violet (UV) radiation is produced from high-energy rays emitted from the sun that lie beyond the visible light spectrum, (beyond the violet/blue end).  When it comes to potential damage to our skin and eyes, we are primarily concerned with UVA and B radiation.  UVA, the sun’s “aging” rays, contribute to early wrinkling and cataracts and these rays travel through clouds, glass, and some clothing.  UVB, known as the sun’s “burning” rays, cause eyelid and other skin cancers, (Melanoma), and sunburn of the eye, (Photokeratitis).  UVB is the more damaging of the two forms, as it is responsible for what we know as “sunburn” and Melanoma.  Both UVA and UVB overexposure may contribute to age-related, macular degeneration of the eye in the area of the central retina.

    Most of us are already aware of the hazards of UV radiation, but as pilots flying at high altitudes we experience greater exposure, so we need to pay even more attention to our own protection, when it comes to both our skin and our eyes.  Scientists estimate that there is a 4% increase in UV radiation per 1000 feet of elevation/altitude gain, (Dr. V.B. Nakagawara, O.D.).  Also, for every 1% of Ozone depletion, exposure to UVB radiation increases by 2%.  Ozone naturally filters out UVB, but at high altitude and at latitudes near the Poles, ozone levels are reduced.  A recent study of Nordic airline pilots conducted over five decades reported that they experienced a .5 percent increase of skin cancers.  Another survey headed by Dr. Gary Butler, (Director of ALPA, Flight Occupational Exposure Research), which was given to over 11,500 airline pilots with at least 20 years experience, reported a 3.5 increased-ratio in melanoma occurrences when compared to the rest of the general population.  So there is an increased skin cancer rate among airline pilots.  It is worth noting however, that neither one of these studies were able to accurately factor in leisure-time sun exposure habits of airline pilots.  Aside from occupational and lifestyle factors, those with fair complexions, red or blonde hair, blue eyes, freckles and who sunburn easily, are most susceptible to development of melanoma.  Lastly, it also worth noting that circadian rhythm disturbances (jetlag), which changes the homeostasis of melatonin, may increase susceptibility to melanoma, as melatonin has been reported to have cancer-protective qualities.

    Okay, I think that is about all of the bad news, so you know what comes next: What can we do to protect ourselves?  The short answer: apply sunscreen with SPF, wear sunglasses with UVA and B protection, and use the shades in the cockpit.  I suppose you could also bid for redeyes.   Sunscreen options are pretty basic.  Just look for a SPF (Sun Protection Factor) of at least 30.  SPF only blocks UVB.  For full skin protection, choose zinc or titanium oxide, but you may look funny with a white nose.  Remember, your eyes are exposed to the same level of UV radiation as your skin is, so wearing sunglasses is essential.  Color and shade have absolutely nothing to do with how much UV blocking power a pair of sunglasses may provide.  The label needs to specifically state UVA and UVB blockage, (rays between 290 and 400 nanometers, nm.).  Expect at least 99% UVB blockage and 60% UVA blockage.  Glare off of cloud decks and reflective surfaces in the cockpit, (like your giant watch), can subject your eyes to 10 to 12 times more light than that needed to see.  For glare protection, look for polarized lenses.  For comfortable vision on sunny days, your glasses should block 75 to 90% of visible light, a level which will also shield against ‘blue light’.  Top-down gradient tinting will be lighter at the bottom of the lens, allowing for a clearer view of the instrument panel.

     There is another type of radiation we are constantly exposed to, known as Cosmic or Galactic radiation.  This type of “ionizing radiation” is transmitted through outer-space in the form of photons and other subatomic particles, and originates from cosmic events such as stellar and solar flares, supernova explosions, and galactic nuclei explosions, not to sound like the late Dr. Carl Sagan.  According to Dr. Gary Butler, Ionization is the primary process by which radiation exposure affects biological organisms.  When atoms or subatomic particles become ionized, they become electrically charged and produce ions.  The earth, being a celestial body, is constantly bombarded by these ionized particles, which vary with the 11-year cycle of rise and fall of solar activity.  The earth’s geomagnetic field provides some protection from incoming radiation, deflecting the incoming cosmic rays, with the least amount of protection provided at latitudes near the Poles.  Exposure increases near the Poles, but does not increase with Flight Level.  So after dropping all of this heavy, Stephen Hawking-esque, sci-fi lingo on you, do you even need to be concerned for your health?  Well the good news is that based on the latest studies of cosmic radiation exposure levels for airline pilots in North America, we are not at any greater risk from an occupational hazard standpoint.  So far, dosages measured have been considerably lower than the occupational limit of 20 mSv per year, than the ICRP recommends for a non-pregnant adult.  Other than causing static on our radios and random interruptions of our navigation systems, we have no reason to fear a solar flare…that scientists are aware of yet anyway.   

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