I dont need a study
Im going from personal experience
I have a tiny ass .2 bowl on my bong and i can do one bowl of that and be good
When i smoke a pipe i have to go through much more than that.
Also i know a guy who drank a bunch of bongwater and he didnt get high:wtf:
Also look at bong water, smell it, taste it, would you rather that crap be in your lungs???