I must ask if you read the entire study,
i didnt, i only read the parts about water filtration because thats what concerned me, i saw that it may filter more thc than tar, but even so that could be because it filter barely any tar and barely any thc.

But this is what caught my interest

Nonetheless, it is still premature to judge that waterpipes are actually unhealthful, since they may filter out other, non-solid smoke toxins occurring in the gas phase of the smoke, which was not analyzed in the study. Noxious gases known to occur in marijuana smoke include hydrogen cyanide, which incapacitates the lung's defensive cilia; volatile phenols, which contribute to the harshness of the taste; aldehydes, which promote cancer; and carbon monoxide, a known risk factor in heart disease. Previous studies indicate that water filtration may be quite effective in absorbing some of these [Nicholas Cozzi, Effects of Water Filtration on Marijuana Smoke: A Literature Review, MAPS Newsletter, Vol. IV #2, 1993]. If so, waterpipes might still turn out to have net health benefits.
This would mean that with a bong you are preventing many of these harmful chemicals from entering your body, and with a pipe you still get the same if not more tar.