“Occasional and low cumulative marijuana use was not associated with adverse effects on pulmonary function.

Marijuana may have beneficial effects on pain control, appetite, mood, and management of other chronic symptoms.

Our findings suggest that occasional use of marijuana for these or other purposes may not be associated with adverse consequences on pulmonary function.”

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3840897/

https://jamanetwork.com/journals/jama/fullarticle/1104848

“A common misconception about medical marijuana is that if inhaled, it will have detrimental effects on the patient’s lungs. However, according to a 2012 study published in the Journal of the American Medical Association (JAMA), this notion is simply untrue; in fact, this study points to an idea quite the opposite: that medical marijuana just might improve lung health under certain conditions.” HTTPS://AGRIMEDINDUSTRIES.COM/2018/06/08/STUDY-SHOWS-MARIJUANA-HAS-A-POSITIVE-IMPACT-ON-LUNG-HEALTH-UNDER-CERTAIN-CONDITIONS/