I have no idea what kind of if big factorys use filters to clean out the smoke before the shoot it into the air but… If a water bong cleans most carcinogens out of (at least tobacco and marijuana) smoke couldn’t they set up some why for the smoke to be filtered through some water to help clean it out. Seems that way any thing that can dissolve in water will stay there instead of going up and dissolving in the rain water. I know then we’d have to do something with the dirty water but we could deal with that later.
I never bought the “water-bongs remove carcinogens from smoke” theory myself. The only difference is that the smoke is thoroughly cooled before reaching the lungs, hence making the puff smoother.
Any tars the water might remove would only be a residual amount. After all, its just bubbles of smoke filled air passing through water, its hardly reverse-osmosis going on here.