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The article published on March 30, 2020, on the JAMA Network Open website has garnered considerable attention recently. Titled “Fine Particulate Matter Exposure From Secondhand Cannabis Bong Smoking,” the article explores the effects of secondhand cannabis smoke exposure. While secondhand tobacco smoke (SHTS) has been linked to various health issues such as cancer, respiratory and cardiovascular diseases, preterm birth, and compromised immune function, a 2016 study on rats demonstrated that secondhand cannabis smoke (SHCS) can impair the function of endothelial cells in blood vessels, suggesting similar harmful effects. This is the first study to investigate the effects of secondhand cannabis smoke from a bong in a social setting.

Studies on secondhand tobacco smoke primarily focus on very small solid particles measuring less than 2.5µm (less than 0.0025 meters) in size. These fine particles can penetrate deep into the lungs and are associated with eye, throat, and lung irritation. Some controversial studies have even suggested that prolonged exposure to these fine particles may elevate the risk of developing lung diseases such as chronic bronchitis, emphysema, and cancer.

For those unfamiliar with the device, a bong is a water pipe through which the smoke from cannabis combustion is inhaled via a water reservoir, which cools and potentially filters the smoke before inhalation. Bongs are popular in both medical and recreational cannabis markets and are commonly used indoors, often in social settings. This typical usage exposes users and others in the vicinity to SHCS, forming the basis of the study.

The study was observational in nature, meaning the authors had minimal interaction with the subjects. All subjects provided their own cannabis and water pipes, and the experimental environment was typically the room and ventilation system within their own homes. In an article interviewing cannabinoid scientist Matt Elmes, PhD by Project CBD, some limitations of the study were highlighted, 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.” This raises questions about the study’s setting and the lack of control over external factors.

Additionally, the carcinogenic potentials of tobacco and cannabis smoke are distinctively different, with tobacco smoke being associated with an increased risk of head, neck, throat, and lung cancers, while cannabis smoke has not been shown to cause these types of cancers. Therefore, comparing the two types of smoke based on their particle size and potential to cause disease overlooks this important distinction.

The study’s conclusion suggests that contrary to popular belief, bong smoking is not safe and promotes indoor cannabis smoking. However, the study design lacked control over numerous confounding variables and essentially measured particulates in a room where a bong was being smoked. Therefore, comparing the potential of SHCS to cause disease based solely on the number of small particles generated to that of SHTC is misleading. Given these limitations and the unique properties of cannabis smoke, it is unclear whether any meaningful conclusions can be drawn from this study.

In conclusion, smoking cannabis in a well-ventilated room rather than in an enclosed space is advisable.