6t%3D1426277337000%26v%3D2%26position%3D3%26c hina_variant%3DFalse&utm_medium=10today.0313&position=3&part=sl&china_variant=False> fortune.com / BY RYAN BRADLEY Companies are using them to make everything from snack foods to clothing to sunscreen. The problem? We know very little about the long-term effects on o... re