As for the environmental issues, i definitely think something needs to be done to make all sunscreens less harmful to the environment especially for the oceans reefs. I can remember many times going to a crowded beach and seeing the sunscreen oil slick in the water. Hopefully someone can find a solution to this problem.

Thanks for this. One of the more attractive features of nanoparticle-based sunscreens is that the nanoparticles can be finely tuned to suppress potentially harmful chemical activity – such as the generation of free radicals in sunlight. But evidence has recently come to light from a rather unusual source that not all manufacturers are taking the necessary steps to avoid the generation of hydroxyl radicals when nanoparticles in sunscreens are exposed to ultraviolet light (see http://community.safenano.org/blogs/andrew_maynard/archive/2008/06/21/nano-sunscreens-leave-their-mark.aspx ).

(I suspect am preempting your next blog entry here…)

It's unclear how much of an issue this in terms of possible skin damage or environmental harm (as the sunscreens are washed off and dispersed), but if there is no regulatory distinction between chemically active and chemically benign nano-ingredients, responsible manufacturers end up being put at a disadvantage while less-responsible (or aware) ones continue to use materials with a poorly understood risk profile.

Something FDA will hopefully be thinking about as the Sunscreen Monograph is updated

Recent studies have found that quantum dots can penetrate abraded skin, and that fullerenes can penetrate flexed skin. And while this does not mean that nanoscale zinc or titanium oxides will also penetrate flexed or abraded skin – the bottom line is we just don’t know.

An additional complicating factor is that different manufacturing processes, as well as different surface treatments can alter physical, chemical and toxicological properties. So not all nanoscale titanium dioxide will have the same profile. This will be the subject of my next blog…

- FoE has not ranked nano-scale ingredients among the worst in their reports because they have not assessed the range of ingredients used in sunscreens. Their reports raise legitimate concerns regarding the safety of nano-scale ingredients only.

- EWG's assessments are driven to a significant degree by extensive evidence showing that nano-scale ingredients don't or barely penetrate healthy skin. This contrasts with the most widely used other ingredients that either absorb themselves or enhance absorption of other ingredients. Further, many sunscreen ingredients breakdown when exposed to the sun, leading to exposures of unknown and unstudied chemicals.

- Ironically, nano-scale sunscreen ingredients are better studied than most sunscreen ingredients even when completely excluding non-nanoscale studies on zinc oxide and titanium dioxide.

Disclosure: I am one of the authors on the EWG sunscreen reports, though I am no longer employed by EWG. The views expressed are my own.