I have read that sunburn is caused from oxidation in and around the skin cells gathers the radiation that burns us.
I sit in baseball fields every other weekend 9 months out of the year. I do NOT burn. Last Sunday, I could hear those sitting under the stadium seats telling my daughters "you need to get your mama under here, she's turning red out there." Pink-up, I did. Burn, I did NOT. I got up Monday all nice and brown, and I'm very fair skinned, thanks to my red-headed daddy.
Following a holistic life-style, taking anti-oxidents, using coconut oil on my skin (a natural sunscreen that allows you to continue making vitamin D while not burning) keeps me from sun-burning ... even when we're winning and I'm sitting behind homeplate from 9am - 6pm.