The sun part 2: sunscreen

As a tree planter, many of my spring and summer days are spent outside, at high altitudes, and in places most notable for their lack of available shade

And yet I never use sunscreen. In part, this is because I don't have to worry about sunburns as much as do the fair-haired, and because I have a mild aversion to skin creams and lotions. But it's also because I've never understood how sunscreens work; and because I've long heard rumors of dire side effects: for example, my ex-physiotherapist once told me that sunscreen causes skin cancer.

However, I certainly appreciate the power of ultraviolet (UV) sunlight, which can sunburn, bleach pigments, and sterilize drinking water. So I can't help but wonder: are my coworkers and I really better off without sunscreen?