We have plenty of evidence that the inhalation of combustion products will have negative health effects. If that's all the study says, then it does not add to

We have plenty of evidence that the inhalation of combustion products will have negative health effects. If that's all the study says, then it does not add to existing knowledge, and really isn't about cannabis at all. That's a kind of uselessness. So why was the study conducted (this way), and why does CNN consider it newsworthy? The answers to those questions might be more interesting than the study itself.