The UV index was first developed by Environment Canada researchers (go figure – a northern latitude weather service!) in the early 1990s, and it has been adapted internationally. Virtually all of you have heard of this measure of ultraviolet radiation exposure, but only some of us pay it enough mind.
Nearly all types of skin cancer are on the rise, including the most dangerous: melanoma. Most skin cancers (not all) are linked to UV overexposure. Some of the overexposure is due to more and more time spent out in the sun, and some of it is due to the mean migration to the sunbelt states, where exposure rates are even higher.
For example, as of this writing, our local UV index for today is 9, or Very High. That’s the second most dangerous of the five categories. But most of the mid-south, south and southwest today are at 11, or Extreme.
UV consists of longwave rays, UVA, which can penetrate deeper layers of the skin, and shorter wave UVB, which produce more damage and burning at the surface.
Most dermatologists recommend using at least SPF 30 for protection, with application of lotions and sprays 15 minutes before exposure. Repeat applications are recommended regardless of label claims. (Heavens! My mom was a sun worshipper who used baby oil and and a little iodine. She didn’t believe me about the worthlessness of that concoction until my dad’s MD verified what I’d told her.)
The index is tied to the forecast peak emissions from the sun when it is overhead, at noon, at a given location. The most dangerous hours for exposure are from 10 a.m. to 4 p.m. However, exposures in mid- to late afternoon increase dangers for UV damage to the eyes due to the angle of exposure, including cataracts and macular degeneration. The hazards are increased at higher elevations (where there is less atmospheric filtering) and by reflection of UV by sand, water and snow.
Exposure is dependent on the clarity of the atmosphere. Basically, even if you don’t know the index number, if you see a dark blue sky overhead, the UV index will be high to very high. If there is some transparent, thin cloud cover, the UV index is reduced somewhat. But thin cirrus clouds with visible sunshine most certainly do not bring meaningful protection. On a day with leaden, gray solid overcast skies, yes, exposure is minimal.
As I have said on TV countless times, UV exposure is not in any way related to temperature. The heat may temporarily redden your skin if you’re sweating away in a volleyball game, but it's not the UV causing the reddening. If we have an unusually chilly but sunny day in the summer, the UV exposure is every bit as high as it would be at 90 degrees.
Tanning beds and sunlamps present an even greater hazard, since they are purposely designed with reflective surroundings to enhance the UV exposure. There is epidemiological evidence that early use of tanning beds increases the risk of melanoma by 75 percent. The number of sunburns one receives over the course of one's life does cumulative damage and increases the risk of permanent damage including early skin aging and cancer.
Lighter-skinned people are at greatest risk, of course, but that doesn’t mean darker-skinned people are immune to sun damage. Bob Marley died from a melanoma by a toenail at age 36, diagnosed too late. Whether that was from UV exposure is uncertain, but many dark-skinned peoples still contract basal cell carcinomas on exposed areas … just not so many as whites.
Finally, automobiles do afford protection from UV, but not quite as much as might be supposed. Windshields, due to their lamination, bring almost total protection. But in most cars, tempered side and rear windows still allow an average of 35 percet of the UV rays to penetrate. Studies show drivers have higher incidence of skin damage on their left arms. In England and Australia, it’s the opposite.
Most financial experts recommending investing in index funds. Maybe I should put a few bucks in UV index funds. Hmmm?