Debbie: "Funny how having a chunk cut from your face will make you a true believer in all this stuff."
Me too. Two out of my face, one on my neck and two on my back. All basal cell which has a FAR better outlook than the melanoma my outdoorsy cousin had on his ear, which spread, and killed him at 41.
A few thoughts, having thought about this a lot, talked to numerous doctors (including my wife and a basal-cell specialist):
The derm guy had a expression that I liked: "roof, hat, shirt, sunscreen". Obviously I like being outdoors, but I have to admit that a roof is a better sunscreen than any clothing or SPF-900. I use that roof trick more in the south, especially in the tropics and even more so from 10 am to 2 pm.
He also pointed out that one should RUN OUT OF sunscreen if you're doing it right. The point is to USE IT UP and then get some more.
Sun exposure is a factor on a population basis (Celts in Australia get more skin cancer than Celts in the UK), but it doesn't explain all skin cancer. People want to know what they can do and shade and sunscreen is something doctors can tell you to do (whereas they can't change your genetics, your past sun exposure, or your chemical exposure).
I'm pretty middle-of-the-road on chemical exposure - for instance, I don't rant and rave about BPA in my Nalgene but I observe that WHO's deep wells in Bangledesh brought up a lot of Arsenic-contianing water and caused a lot of skin and organ cancers before they realized it. All 5 of my skin cancers were 12-24 months after living in a place with high Arsenic in the water. In my 51 years, all 5 landed in the same year?!? And now none for the last decade?!? From that temporal cluster, I conclude that FOR ME, I need to avoid Arsenic expsoure. YMMV.
My wife and I have a running joke about "a N of 1" referring to anecdotal evidence which is considered crap in medical circles. Medicos run their studies on 2,000 or 40,000 patients and have statistical power in that. In my work, I have to tease as much understanding as I can from very little data. Looking at my own face in mirror versus my exposure I note two trends: More veggies, especially the brightly colored and cruciferious ones (reportedly high in flavonoids and anti-oxidants), seems to help clear up the little scaly patches, the bits of weaker skin, the places the derm guy calls "pre-cancerous lesions.
The other, odder, trend is that some spots get worse in the winter only to get better in the summer (dramatic change in exposure in Alaska). My theory is that the exposure puts my skin into repair mode. I stress YMMV, but it is consistent for me.