The workers were 'exposed to' dangerous chemicals. [=they were placed in conditions that left them unprotected from dangerous chemicals]
His mistakes have 'exposed' him 'to' ridicule. [=he has been ridiculed because of his mistakes]
Children are being 'exposed to' violence on television.
(..) Go be a doctor. Go be a doctor while you still can. I can't. I won't. I'll be a doctor, but my work is here with you now. That virus that I was exposed to... ...whatever it is, it has a cure. You held it in your hand. How many other lives can we save? Look... ...if I quit now, they win. (..)1998 The X Files