@burcidi-- UV rays! Most people don't realize this but UV rays are a mutagen too. That's how people get skin cancer if they're exposed to too many UV rays without protection.
I had an aunt pass away from skin cancer and I never step out of the house without applying lotions with UV protection. I also avoid being in the sun if I can between 11am and 4pm.
By the way, just because a lotion has SPF doesn't mean that it has UV protection. They're different things! There are different sun rays and UV is the most dangerous and it causes mutations in our cells and DNA!