My daughter Teal rang me this week asking what ingredients to avoid in sunscreens. the very next day I received an email promoting one that looked promising, at first glance. It had a list of natural ingredients at the top of the web site but when I read the fine print it contained Micronised Titanium Dioxide. Here is some interesting data on the difference between products at normal size being non-toxic and micronised or nano-particles (really, really small ones) being destructive to cellular health.
Toms Blog on Life and Livingness