Nanoparticles of zinc oxide and titanium dioxide are not safe-
This is very important for outdoor enthusiasts.
There has always been controversy over sunscreens — about their effectiveness, screening UVA versus UVB, and migration of sunscreen chemicals into your body. Two you could always count on for safety, however, were the mineral oxides (zinc oxide and titanium dioxide), bright white and inert.
However, people didn’t like the white film they left on their skin.
In recent years very small particles over many elements and chemicals have been developed. The physical and chemical properties of these tiny particles are amazing, useful, and sometimes dangerous. Nano-sized particles of a chemical often behave very differently than powders of a larger size. With zinc oxide and titanium dioxide, the white film and somewhat greasy feel disappears. They are invisible soon after application. They still reflect UV rays. However, they sink deep into your skin. This allows the reflected rays to bounce sideways into your skin. Much worse, some of the oxide sinks right through your skin into your blood. From there they are distributed throughout your body.
These are very hard powders, even nanosized. Your body cannot expel them. They stick in your organs and they provide a surface for many kinds of chemical reactions. Almost all sunscreens with these oxides today are nanosized, and they don’t have to tell you.
Friends of the Earth just put out an alert on them, but I have rejected their use for about three years now. You can still get the effective, safe, old-fashioned oxides, but it usually means ordering online. You won’t find them at the grocery or drug store. I ordered some at Amazon.com.