What type of problem does he have?

Well i know this kid and he is pretty normal except for the fact that today I saw him scraping dirt (or God knows what) off his shoe and then eating it. He also picks his boogers and then eats them. I am POSITIVE of this because i saw it with my own eyes. He is not mentally retarded because he is smart in school but this isn't normal and i *really* wanted to know what was the matter with him.