no you don't consume carcinogens from eating it, (correct me i'm wrong anyone, but i'm pretty damned sure of this...) no a water bong does not filter out all the carcinogens, and actually according to those nomrl studies, it showed it was even taking away 'the high' (i want to say thc here, but someone will come back and say thc isn't the only thing that gets you high, which i know, but i can't think of the right word to use in this situation..)