Fine Particulate Matter Levels Up With Social Cannabis Smoking

PM₂.₅ level increases with smoking in the home, decays gradually after smoking stops, and remains elevated indoors 12 hours later

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WEDNESDAY, April 6, 2022 (HealthDay News) -- In-home social cannabis bong smoking is associated with markedly increased levels of fine particulate matter in indoor air, according to a research letter published online March 30 in JAMA Network Open.

Patton Khuu Nguyen and S. Katharine Hammond, Ph.D., both from University of California at Berkeley, measured fine particulate matter (PM₂.₅) levels from social bong smoking to quantify secondhand cannabis smoke (SHCS) levels from cannabis smoking in the home. Measurements were taken before, during, and after eight cannabis social-smoking sessions in a living room.

The researchers found that home cannabis bong smoking significantly increased PM₂.₅from index levels (conditions existing before the smoking began) in all sessions by 100-fold to 1,000-fold for six of the eight sessions. Two sessions had high levels to start with, but PM₂.₅significantly increased more than 20-fold (P < 0.001 for all sessions). Mean PM₂.₅ after 15 minutes of smoking (570 μg/m3) was more than twice the U.S. Environmental Protection Agency hazardous air quality threshold (>250 μg/m3). During smoking, the concentration increased to a mean of 1,300 μg/m3. Half an hour after smoking ceased, mean concentration declined to 78 percent of peak and reached 31 percent after 110 minutes. Twelve hours after smoking stopped, PM₂.₅remained elevated at 50 μg/m3, more than 10 times the background concentration. Compared with cigarette or tobacco hookah (waterpipe) smoking, cannabis bong smoking in the home generated four times greater PM₂.₅ concentrations.

"This study’s findings suggest SHCS in the home is not safe and that public perceptions of SHCS safety must be addressed," the authors write.

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