JAMA Publishes Study on Secondhand Cannabis Smoke

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The Journal of the American Medical Association, or JAMA, this week published a study comparing data on tobacco smoke with the potential effects of secondhand smoke from cannabis. Titled, “Marijuana, Secondhand Smoke, and Social Acceptability,” the study cited an event, held on 4/20 Day in San Francisco’s Golden Gate Park.

It described 15,000 event attendees, who reportedly smoked marijuana to the extent that a smoky cloud was visible half a mile away, at the University of California, San Francisco. Study authors argued if a similar event had been held for cigarette smokers, outcry and public health laws would have stopped it from taking place. However, unlike cigarettes, those exposed to secondhand cannabis smoke often feel that inhalation is harmless or even good for them.


“The evidence that secondhand exposure to marijuana smoke, like the evidence for all health effects of marijuana, is more limited than for tobacco,” the study read.

“But smoke from any source is a complex mixture of thousands of chemicals, including ultrafine particles and toxic gases. Other than nicotine and cannabinoids, tobacco and marijuana smoke are similar. Indeed, the California Environmental Protection Agency identified marijuana smoke as a human carcinogen based largely on the smoke’s toxicology,” authors added.

While recognizing the lack of research on the effects of secondhand cannabis smoke specifically, authors recommended that lawmakers pursue regulations for public cannabis consumption similar to those currently applied to tobacco smoke.

“This evidence supports maintaining and expanding clean indoor air laws to include marijuana as part of a public health framework for marijuana regulation. Stressing the right of all to breathe clean air should also be at the core of educational and legislative efforts to reinforce the marijuana smoke-free norm for everyone.”

Study authors are Stanton A. Glantz, PhD; Bonnie Halpern-Felsher, PhD; and Matthew L. Springer, PhD, with the Center for Tobacco Control Research and Education, Cardiovascular Research Institute, Department of Medicine (Cardiology), at UCSF.

The National Institute of Drug Abuse, the California Tobacco Related Disease Research Program, and the Elfenworks Foundation funded the study, in part.

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