What We Still Don’t Know About Sunscreens

"A yearlong study by the Food and Drug Administration has produced sobering data indicating that a form of vitamin A, retinyl palmitate, may accelerate development of skin tumors and lesions when applied in the presence of sunlight."

http://roomfordebate.blogs.nytimes.com/2010/07/05/what-we-still-dont-know-about-sunscreens/