The sunshine D-lemma
Sunlight causes skin cancer, but it also produces vitamin D, a substance that seems to prevent some types of cancer and possibly other diseases.
Carcinogen is a word that jumps off the page. It makes us think of nefarious chemicals and noxious pollutants.
So it's startling to see sunlight — or, to be more precise, the invisible, ultraviolet portion of sunlight — labeled a carcinogen, a term that can be applied to anything believed to cause cancer. There are some nuances to the evidence, but overall, there's not much question that exposure to ultraviolet light is a risk factor for all three types of skin cancer: basal cell, squamous cell, and melanoma.