SUNSCREEN in UV

I'm rather shocked that the true meaning of SPF is not discussed. SPF is the hour exposure equivalent. So 30 SPF allows you to be exposed for 30 hours, while receiving the exposure of 1 unprotected hour. Understanding this, there are a variety of questions that come into play. 1. What is your body's ability to  handle and repair exposure damage. 2) Can higher levels of exposure be beneficial? For 1, there is a threshold of repair and replacement that the body can handle with no adverse effects. For 2, they answer is yes. People living in Denver which have higher background radiation levels actually have lower cancer risk because the cellular repair mechanisms are more activated. To be in a zero-exposure environment would lead to the shutdown of the mechanisms and mutations would become prolific. So, my own reasoning is this: Use a SPF which is rated for how may hours I can handle before burning. I estimate 1 hour, (less in spring and more going into fall). So if I will be out for 8 hours, I use SPF 8. I get no more damage than by body can handle, and I develop a tan (natural protection) which is usable even when not wearing sun screen. 

I think a lot of the controversy comes from people not understanding what SPF means. I've been pitched sunscreens that don't cause cancer, and I believe them on a compositional basis. However the USE of that same sunscreen may. There is actual statistically significant* (*formal definition) evidence that people who use sunscreen have HIGHER risk even though they don't burn. My take on it is this: think about it this way: if you use sunscreen as a block, you never let your body develop it's own protection. Any time you are not wearing sunscreen you're in a more vulnerable state, letting those photons damage DNA. However if you use sunscreen to develop your tan, providing natural protection, you expose your self to less "chemicals" and reduce your need for such chemicals. 

Finally, do wear "appropriate" sunscreen but *always* make sure your glasses and sunglasses are UV rated. UV accelerates cataract development, and while we have cataract surgery, nothing is as good as your natural lens!