Bad Wigins wrote:
All you chickens so scared shitless of the life-giving sun will be fat and useless before age 35 because your T levels will spiral away to nothing just like Ryan Hall, due to not getting vitamin D the way nature intended, including seasonal variations. You all keep your skin in a state of perpetual winter and will lose first your muscle and then your bones. Then you will be all proud of your spotless fair skin as you sit helpless in a wheelchair with two broken hips.
^^^this is a display of ignorance.
Solar radiation is as carcinogenic as, if not more than, smoking. Sure, there are centenarians who have been life long smokers. But you don't want to bet on having superior genes.
Several posters have it right and some don't get the full picture, while a few are out right ignorant. It is a real issue, not just some trace chemicals thing that might be cancer-prone. The UV-A part of the radiation spectrum is the most problematic, as culprit of skin cancers and AGEING. UV-B on the other hand, gets you sun burns and makes some contribution to skin cancers BUT it also is what's needed to produce vitamin-D in your body (15min/day of sun exposure in summer will be sufficient).
Here're some ways to avoid UV radiation:
1) do your runs in the dark (at night)
2) do them early in the am or late in the pm. When sun is low in the horizon, the path of sun light going through the atmosphere is lengthened and thus reduced by ozone absorption (take vit-D supplement or drink fortified milk to keep at healthy vit-D level). NOTE that this has LITTLE to NO help regarding reducing UV-A, which is outside the ozone absorption band (so if you don't get in the shade, you'll still get aging skin and cancer risks);
3) run at the times as in 2) nd run in the shade. You get more shade when sun angle is low;
4) wear hats/caps and proper clothes for long sun light exposures (regarding blocking UV-A, it's easier to block in the mid-day than early-am/late-pm by wearing a cap as the sun is right above your head.)
5) wear sunscreen with proper UV-A protection (at this moment, New York city is considering putting sun screen dispensers in public places. you're lucky if you're a new yorker)
6) don't run.
Having said the above, I rarely use sun screen. But I try to avoid long exposure in the sun in daily life. And most my runs are done in the afternoon at a local greenway with a lot of shade after work or early morning on weekends.
My advice:
Use sun screen if you can when you should.