AmandaKDT is absolutely right. You have to talk to the parents. If you haven't already, you don't know if this behaviour is worrying them too. If they are new parents or haven't ever seen a child do this kind of thing, they might be thinking the same as you. "Does my daycare provider think I'm hurting him?"
I too have had children who do this kind of thing. Maybe not to this extent, usually it is the same children that take other things to the extreme. The ones who chew rocks, (no kidding) take every piece of food and roll it around in their fingers, eat paint, etc.
If you keep track of the incidents, when, where, how, you may see a pattern. Does it happen more right before or after a transition in the day, when he's hungry, bored, or tired? Sharing this info with the parents might help them if they discuss it with his doctor.