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Cannabis Bong Smoke Isn’t Safe to Inhale, Says Study

By Leo Bear-McGuinness

Published: Mar 30, 2022   

Image credit: Jeff W via Unsplash

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Hit the bong at your own risk. That’s the message from scientists in a new research letter published in JAMA Network Open.

After a unique study, which involved measuring cannabis smoke from eight separate smoking sessions, the researchers concluded that bong smoke isn’t safe to inhale.

Indeed, the researchers found that after just 15 minutes of bong smoking, the average levels of fine particulate matter (PM) in the air can be more than twice the threshold deemed hazardous by the US Environmental Protection Agency (EPA).

Bongs gone wrong

According to some surveys, around 27 percent of young adults believe second-hand cannabis smoke exposure is safe to inhale, even though the smoke often contains high levels of PM.

To determine just how much PM is produced from bong smoking, two researchers from the University of California, Berkeley, brought an aerosol monitor to eight different “social smoking sessions” that took place in the same living room.

“These were social/recreational sessions and organized independently by another college student separate from the study,” S. Katharine Hammond, a professor of environmental health sciences at Berkeley and co-author of the study, told Analytical Cannabis in an email.

“We were able to use these opportunities to make our measurements. We had no interaction with the smokers during the bong smoking event.”

PM measurements were taken before, during, and after each smoking session. The monitor itself was placed in the room “where a nonsmoker might sit” to help make the findings more relevant to inhalers of second-hand smoke.

Hammond and her colleague found that bong smoking significantly increased the levels of PM in the room; in one case, the post-smoking levels were 1000 times higher than the levels recorded before smoking.

During the first 10 minutes of smoking, average PM concentrations increased to 410 micrograms per cubic meter (μg/m3), then to 570 μg/m3 after 15 minutes, to 1000 μg/m3 after 30 minutes, and went as high as 2500 μg/m3 in one session. All these measurements are significantly higher than the “hazardous” air quality threshold of 250 μg/m3 set by the US EPA.

After some calculations, the researchers concluded that cannabis bong smoking in the home generates four times as much PM concentrations than cigarette or tobacco hookah smoking.

And these high levels of PM could pose a health risk to the smokers and those sitting near them.

“There is extensive evidence of the adverse health effects of particulate matter at concentrations substantially below those measured in homes during and after bong smoking,” Hammond told Analytical Cannabis.

“To quote from the recent EPA report: there are ‘consistent positive associations between short-and long-term PM exposure and respiratory and cardiovascular effects and mortality.’”

No smoke without risk

Cannabis smoke is known to contain many of the same chemicals present in tobacco smoke. Yet the effects of these chemicals may be altered when present with cannabinoids, according to some research.

One scientific review published in Cancer Epidemiology Biomarkers & Prevention in 2015 found no association between cannabis use and lung cancer despite marijuana smoke containing many known carcinogens in amounts comparable with those found in tobacco smoke. One explanation for this null association, as posited by the review, is that cannabinoids like THC counteract the carcinogens with their tumor-suppressant effects, which have been evidenced in several cell culture and animal models studies.

But other, more recent studies have documented the negative health risks second-hand cannabis smoke can pose.

A study published in Pediatric Research last year found that the children of regular cannabis consumers who smoke or vape come down with viral respiratory infections more often than children whose parents don’t smoke. However, other risks known to be associated with second-hand tobacco smoke, such as ear infections or asthma attacks, weren’t reported more frequently in the children of frequent cannabis users.

Another paper published in EClinicalMedicine last year found that cannabis smoking raises the levels of the toxic chemicals acrylonitrile and acrylamide in the blood, but not to the same extremes seen in tobacco smokers.


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