How can breach the subject and get him to listen without puting him on the defensive and being callous.

My boyfriend is a smoker. He knows I'm against it, but because of the extreme infrequency of his use, it's never bothered me. Recently it's become apparent at work that the company he works for could be going under and he would be out of a job. Because of this stress he's started smoking very heavily. Of course, this is a hard time for him and I want to be supportive and not put any undue pressure on him, but the smoking makes his skin, clothes, hair, and (especially) breath reek. It's so offensive to me I don't want to kiss him or be intimate with him, but when I try to talk about it with him, he thinks I am overreacting and being intentionally being mean. I do not want to be insensitive but at the same time I really don't think he understands how much it bothers me. Help!