Sun and Active Patients
Sun and Active Patients
abstract & commentary
Synopsis: Repeated exposure to ultraviolet light can result in premature aging of the skin as well as an increased risk of precancerous and cancerous (basal cell carcinoma, squamous cell carcinoma, and malignant melanoma) lesions.
Source: Davis J. Sun and active patients. The Physician and Sports Medicine 2000;28:779-785.
Davis reminds us that sunburn (the acute manifestation of overexposure to sunlight) is not the only danger of excessive exposure to sunlight. Solar radiation spans wavelengths from 270-5000 Newton meters (Nm), and includes infrared light, the light that warms us (wavelength > 800 Nm), visible light at the mid spectrum range (400-800 Nm), and ultraviolet (UV) A, B, and C from 320-400 Nm, 290-320 Nm, and 200-290 Nm respectively.
UVA, the wavelength of light responsible for aging, is poorly absorbed by the ozone layer; whereas UVB, responsible for producing sunburns as well as precancerous and cancerous lesions, is moderately absorbed by the ozone layer. UVC, also found in halogen light bulbs, is well absorbed by the ozone layer and therefore very little UVC reaches our skin.
Since there is less atmospheric ozone filtration when the sun is directly overhead (10 a.m.-2 p.m.), the chance of sunburn is greatest at this time. Not only does the sun’s radiation cause sunburn and pre-cancerous and cancerous lesions, but it also triggers dermatological diseases such as xeroderma pigmentosum, oculocutaneous albinism, and lupus erythematosis. Additionally, sunlight can precipitate photosensitivity induced by oral medications, such as sulfa drugs and oral contraceptives, and NSAIDs, such as naproxen sodium.
Exposure to UVA and UVB can suppress certain delayed-type hypersensitivity responses such as allergic contact dermatitis; however, the immunosuppressive effect of UV rays may also be responsible for the reoccurrence of cold sores (herpes simplex labialis).
Davis’ suggestions for protection against the harmful side effects of UV light include avoiding the sun during midday when UV rays are more intense, wearing clothing (hats, long pants, long sleeved shirts) to shield the skin from UV rays where feasible, and using physical sunscreens such as titanium dioxide and zinc oxide or chemical sunscreens of at least a no. 15 sun protective factor (SPF).
Comment by Letha Y. Griffin, MD, PhD
Although most sports medicine physicians are excellent at reminding athletes to stay well hydrated during the heat of summer, few emphasize the significant risk of exposure to the UV rays present in our surroundings. Unfortunately, athletes exercising in the heat are unable to use clothing such as long sleeved shirts and long pants to screen out the harmful effects of UV light, as such would promote overheating during exercise. Sun visors or hats, though, are often feasible. Moreover, athletes should be reminded to wear chemical or physical sun screens and to apply them liberally and frequently when exercising in the sunlight. One should remember that although infrared radiation is absorbed by water droplets and clouds, UVA and UVB are not well absorbed by clouds and hence one can still be exposed to the harmful effects of the sun’s radiation even on cloudy days.
Coaches should be reminded to try to minimize the number of practice sessions scheduled for midday when the heat index is higher and the risks of exposure to the harmful effects of sunlight are also higher.
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