Yes. Pencil lead is actually a non toxic material called graphite. Unpainted pencils only a problem if baby bites off chunks and chokes on them. I don't believe that the paint on pencils is a problem if they are made in the us. I have reservations for any painted material coming out of china as they may have toxic material in the paint.
No. -lead pencils contain graphite, not lead, so lead poisoning is less of a concern. Just remember to exercise common sense! -when older kids gnaw out of habit or nerves--let it slide. Pay too much attention and you risk reinforcing the habit. But, the younger the child, the less of a good idea it is to chew on a pencil--or any writing implement, for that matter!
No. It is not safe for young children to chew on pencils, nor on any breakable items, because they will choke on the parts. The black material is graphite powder held together by mixing in some clay-like materials. The materials mixed in with the graphite, the paint on the pencil, and the eraser plus the metal ring, should all be free of lead, if manufactured in the United States.