"Scientists are preemptively testing the potentially ill effects of the tiny molecules and even atoms engineered at the scale of one billionth of a meter or smaller."
Carbon nanoparticles appear to be benign when fed to fruit fly larvae, but adults exposed to the nanoparticles in powdery form are not as lucky. Research led by David Rand and Robert Hurt show two varieties of carbon nanoparticles stuck to the flies, impeded them from climbing and ultimately caused them to die.
See full article at Scientific American:
See Brown news release: news.brown.edu/pressreleases/2009/08/nanotoxicity