A good article on nano-particles in sunscreen including detailed information on the EWG's findings:

http://askanesthetician.wordpress.co...and-sunscreen/

This is why I wanted to find a barrier (zinc/titanium dioxide) sunscreen:

"Sunscreens without zinc or titanium contain an average of 4 times as many high hazard ingredients known or strongly suspected to cause cancer or birth defects, to disrupt human reproduction or damage the growing brain of a child. They also contain more toxins on average in every major category of health harm considered: cancer (10% more), birth defects and reproductive harm (40% more), neurotoxins (20% more), endocrine system disruptors (70% more), and chemicals that can damage the immune system (70% more) (EWG 2007)."