Titanium Dioxide. Titanium is one of the physical sun blocking agents found in certain sunscreens. I recommend the physical blocks (zinc and titanium) because they have a very good safety profile and work very effectively. If you are going to be in the sun - use a minimum of SPF 15 - follow product directions.
You need metal. Sorry, I don't mean the music. You should always have a metal such as zinc or titanium oxide in your sunscreen. Uva radiation, which are the aging rays are not prevented by the spf rating. Spf only refers to uvb, the cancer-causing rays. Think of the metal as reflecting the suns rays away from you. It is absolutely essential to total sun protection.