Rising Mercury Part 2 - Health Concerns

Skin Cancer
Runners and cyclists spend a lot of time training outside, in the sun, and are therefore at a greater risk for developing skin cancer compared to the vampires from Twilight. In order to protect your skin from the effect of these harmful rays, Deena Kastor recommends using a waterproof sunscreen that's at least SPF 30 (apparently 56% of runners don't wear any sunscreen). In order to avoid the "caking" effect, apply sunscreen 20min before you head out to give it time to absorb into your skin. Also, consider wearing protective clothing (i.e., fabrics with an SPF rating), sunglasses, and/or a hat.

Hydration
Drink too little, and you'll dehydrate... drink too much and you run the danger of suffering from hyponatremia. The ACSM recommends drinking between 16-27oz of fluid per hour. In order to figure out how much fluid you should be drinking, weigh yourself before and after running for 1 hour. Every pound lost equates to 16oz of fluid (make sure to keep your electrolyte levels in check with energy gels, sports drinks, etc. for runs lasting more than 60 minutes). I also came across this article which separates "facts from fiction" with respect to hydration:

• It IS BETTER to drink small amounts of fluid throughout the day vs. trying to drink a whole bunch right before you head out the door because you realize that you haven't been drinking a whole ton and probably should (the stomach can only process 7oz fluid / 15min)
• Caffeine does NOT cause dehydration (at least if your "used to it" and consume moderate amounts throughout the day)
• You do NOT need to limit your sodium consumption... in fact, athletes probably need to consume more than the average person to replace what is lost (however, most people consume way too much sodium, so you can probably get away with just eating normally)