It is far and away irrisponsible to call a health effect a myth because one paper suggests an opposite effect for light to moderate users. Considering we DO know what we are inhaling, and we DO know it causes massive problems for other smoked substances, it is rational to think that there are likely related effects. Until we can identify that these effects are NOT occurring, we should definitely assume that you can get lung cancer by inhaling massive amounts of carcinogens.