The point I was trying to get to with the cigarettes is that some PN's are caused by chemical exposure. Have you ever looked at what chemicals are in a cigarette besides the nicotine?

Maybe seeing the list will show you what I mean...it's a very long list. Chemical list for cigarettes.http://quitsmoking.about.com/cs/nico...ngredients.htm

Has to make one wonder especially in a case of PN when no cause is found.