After knowing that Titanium Dioxide could both harm and help its user, researchers decided to test different forms, or isomers, of TiO2 on pig skin to see which of the compound's structures was safe for use. Personally, I didn't know that pig skin is what is used to test human skin care products most of the time (I'd rather not equate my skin to that of a pig's, but I mean okay). At any rate, the skin was tested under indoor UV rays. There are two widely used crystalline forms of TiO2 used in sunscreen; Anatase and Rutile. On the pig skin, Rutile was found to wash off easily and had little to no effect. This was not the case with Anatase which did not wash off easily and caused significant damage to the top layer of skin, even though the UV rays were weak and indoors.
The picture above shows that the Nano-TiO2, or Rutile, does not penetrate the skin, but only stays on the surface to shield from harmful UV rays; whereas the Anatase and Rutile together as well as the Anatase alone sinks below the surface of the skin. The Anatase and Rutile combined still goes slightly below the surface, so it was concluded by the researchers that Rutile alone is the safest for human use.
So if you are looking for sunscreen (for next year of course since fall is now upon us), be sure to look for Rutile so you end up unscathed by both sun and sunscreen.
1. American Chemical Society (2013, September 25). Common cosmetic and sunblock ingredient, titanium dioxide, may have potential health risks
2. Francesco Turci, Elena Peira, Ingrid Corazzari, Ivana Fenoglio, M. Trotta, Bice Fubini. Crystalline phase modulates the potency of nanometric TiO2to adhere and perturb the stratum corneum of porcine skin under indoor light.. Chemical Research in Toxicology, 2013; : 130912183629009 DOI: 10.1021/tx400285j