An article published in the JAMA Network Open website on March 30, 2020 has been receiving a lot of interest lately. The article, titled “Fine Particulate Matter Exposure From Secondhand Cannabis Bong Smoking” [ https://jamanetwork.com/…/jamanetwo…/fullarticle/2790510] examines the question. Secondhand tobacco smoke (SHTS) has been implicated as a causal link to cancer, respiratory and cardiovascular diseases, preterm birth, and decreased immune function. Secondhand cannabis smoke (SHCS) has been shown to impair the function of endothelial cells located in blood vessels in a study performed in 2016 on rats [https://www.ahajournals.org/doi/10.1161/JAHA.116.003858], suggesting it may have similar effects. This is the first study to consider SHCS from a bong in a social setting.Secondhand tobacco smoke studies examine the very small solid particles that are less than 2.5µm (less than 0.0025 meters) in size. Particles this size and smaller can travel deeply into the lungs and it is these particles which are associated with eye, throat and lung irritation. Although controversial, some studies have suggested that breathing these fine particles over a long period of time may increase the risk of developing lung disease such as chronic bronchitis, emphysema and cancer.For anyone unfamiliar with the device, bong is a water pipe in which the smoke from cannabis combustion is inhaled through a water reservoir which cools and perhaps filters the smoke before inhalation. They are popular devices for the medical and recreational cannabis markets and are usually used indoors, often in social settings with others. The typical use exposes users and others in the room to SHCS and was the premise for the study.This study was observational meaning the authors had little interaction with the subjects. All subjects provided their own cannabis, water pipes and the experimental environment was whatever room and ventilation system the subjects had at home. An article interviewing cannabinoid scientist Matt Elmes, PhD by Project CBD (https://www.projectcbd.org/) points out some of the flaws in the study including the fact that “Several smokers smoked at their own volition, ad libitum, in a social setting of their own choosing, not an experimental setting, and without any instructions or limitations from the investigators.” Eames states “Since the participants smoked ‘in a social setting of their own choosing’ and were not given any other instructions, it seems likely that the smoke generated from a single person smoking a bong wasn’t the only thing detected. There could have been several friends in the same room who were also hitting the bong [and possibly smoking tobacco], which would not be unusual. This would seem to be at odds with the air quality studies set up in a single tobacco smoker’s home.” In addition the carcinogenic (cancer causing) potentials of tobacco and cannabis smoke are distinctively different. Whilst tobacco smoke (and presumably SHTS) is associated with an increased risk of head, neck, throat and lung cancers, cannabis smoke has not been shown to cause these cancers. It is these cancers which have been associated with the chemicals contained and particulate matter contained in the second hand smoke. The authors of the study are likely comparing apples to oranges.The conclusion of the authors is that “This cohort study suggests that, contrary to popular beliefs, bong smoking is not safe. Decades ago, many people thought SHTS [secondhand tobacco smoke] presented no health risk to nonsmokers. Scientific research since then changed this perception and led to smoke-free environments. Incorrect beliefs about SHCS safety promote indoor cannabis smoking.”The study design was insufficient in controlling for the many confounding variables and was just essentially measuring particulates in a room where a bong was being smoked. Comparing SHCS potential to cause disease based on the number of small particles generated to that of SHTC is a fallacy. Tobacco smoke and cannabis smoke are not at all the same; equating particle size in smoke to disease causing potential ignores this important difference. A look at the funders of the study (University of California (UC) Smoke- and Tobacco-Free Student Fellowship from the UC Office of the President (UCOP) suggests perhaps another motive in the conclusions drawn.Consideration of this study leaves many others, myself included, to determine that no useful conclusions can be drawn from this article. But smoking cannabis in a well ventilated room rather than “hot boxing” is probably a good idea.