debate goes on for ever, why does the research only come now in the past 5 years or so. why didnt it come out in the 70s with conventional smoking. there are now also nicotene free steam stones that have no tabacco in them. they look like gravel that soaked in honey. I think its correct in saying that the volume taken in, in an hour session is greater than 100 cigarettes. but I disagree to believe that its half as bad as 50 cigarettes. for example if you go into a closed room for 1 hour with a hookah or even two pipes with guys smoking strongly. 2 pipes puffing & blowing out clouds of smoke even a non smoker wont be bothered. but lets go into the same room with one guy smoking on a cigarette & see if the non smoker can sit in that room for the hour. then again noboday smokes for an hour, the pipe only burns for about 30 min.