I anticipate that we'll start hearing more and more about nanotechnology -- or the engineering of extremely tiny particles for use in food, medication, supplements, and personal care -- over the next two years as more science emerges. In the meantime, it turns out that even if the EWG says nanosize particles are safe for use in physical sunscreens, they may not be very safe for the environment.
A study performed at the University of Toledo showed that nanoparticles may damage beneficial microbes that play important roles in ecosystems and in treating wastewater. The nano-titanium dioxide particles get washed off in the shower and end up in municipal sewage treatment plants. Other nanoparticles that may negatively affect beneficial bacteria in the environment include silver, zinc oxide, and copper oxide.