.... if eaten, according to the recent study from the University of Utah, which showed that inadvertently consuming even small amounts of zinc oxide nanoparticles in sunscreen endangers colon cells. And ingesting the stuff isn't that much of a stretch, considering all that transpires--and perspires--during the summer when you're under the pounding sun. And that your kids are playing and eating and swimming with sunscreen on their hands. Plus, consider that most of your chapsticks have an SPF (and some, yes, with nanoparticles). The study found that a nano-based formula was twice as toxic to colon cells as the formula that used larger particles.