What's the benefit/risks of nanoparticles having a large surface area to volume ratio?

BENEFITS: - Invisible as sunscreens - can be used as catalysts (making reactions more effcient) - used on self-cleaning window panes (catalyse the breakdown of dirt in the presence of sunlight) POSSIBLE RISKS: - Very small, possible to breathe in or pass into cells - Once in the body, may catalyse reactions that are harmful - Risks are hard to identify as modern nanoparticulate materials have only become common recently