I suspect they will be determined to be a carcinogen and banned.
***That rings a bell. I think I remember hearing about CNTs causing cancer. The thing is, they’re so small that they disrupt cell membranes very easily.
It's not just the size, it's the shape as well. "Long and skinny". The carcinogenic types of asbestos (not all the different minerals that comprise the broad class "asbestos" are carcinogenic) have a similar shape.