Original sentence: The reason is that waterpipes and filters filter out more psychoactive THC than they do tars, thereby requiring users to smoke more to reach their desired effect.The study does not, however, rule out the possibility that waterpipes could have other benefits, such as filtering out harmful gases such as carbon monoxide
Edited sentence: However the studys authenticity is doubted as THC is not water soluble and can not be contained in water.They claimed the reason is that waterpipes and filters filter out more psychoactive THC than they do tars, thereby requiring users to smoke more to reach their desired effect