Abstract
Fifteen states have legalized the sales of recreational marijuana, and California has the largest sales of any state. Cannabis is most often smoked indoors, but few measurements have been made of fine particle mass concentrations produced by secondhand cannabis smoke in indoor settings. We conducted 60 controlled experiments in a 43 m 3 room of a residence, measuring PM 2.5 concentrations, emission rates, and decay rates using real-time monitors designed to measure PM 2.5 mass concentrations. We also measured the room's air exchange rate. During each experiment, an experienced smoker followed an identical puffing protocol on one of four different methods of consuming marijuana: the pre-rolled marijuana joint (24 experiments), the bong with its bowl containing marijuana buds (9 experiments), the glass pipe containing marijuana buds (9 experiments), and the commercially available electronic vaping pen with a cartridge attached containing cannabis vape liquid (9 experiments). For comparison, we used the same puffing protocol to measure the PM 2.5 emissions from Marlboro cigarettes (9 experiments). The results indicated that cannabis joints produced the highest indoor PM 2.5 concentrations and had the largest emission rates, compared with the other cannabis sources. The average PM 2.5 emission rate of the 24 cannabis joints (7.8 mg/min) was 3.5 times the average emission rate of the Marlboro cigarettes (2.2 mg/min). The average emission rate of the cannabis bong was 67% that of the joint; the glass pipe's emission rate was 54% that of the joint, and the vaping pen's emission rate was 44% that of the joint. The differences compared to the joint were statistically significant. • 60 experiments comparing indoor PM 2.5 from secondhand marijuana & tobacco smoke. • The marijuana joint's emission rate was 3.5 times that of the tobacco cigarette. • All the cannabis sources had PM 2.5 emission rates greater than tobacco cigarettes. • The order of cannabis emission rates was joint, bong, glass pipe, and vaping pen. • The vaping pen's mean decay rate exceeded the other sources' mean decay rates.
Highlights
The District of Columbia and 15 US states – Alaska, Arizona, Cali fornia, Colorado, Illinois, Maine, Massachusetts, Michigan, Montana, Nevada, New Jersey, Oregon, South Dakota, Vermont, and Washington – have legalized recreational marijuana sales, but few research studies have measured exposure to secondhand marijuana smoke in everyday settings
A smoking ma chine may reduce experimental variability, we focused on determining whether the differences between the mean emission rate of the prerolled marijuana joints and the mean emission rates of the other sour ces, including the tobacco cigarettes, were statistically significant
The background concentrations were subtracted from the measured PM2.5 concentrations in Table 1, and the last two columns show the background PM2.5 concentrations were much smaller than the background-corrected maximum PM2.5 concentrations measured in the Measured Maximum PM2.5 Concentrationa ymax μg/m3
Summary
The District of Columbia and 15 US states – Alaska, Arizona, Cali fornia, Colorado, Illinois, Maine, Massachusetts, Michigan, Montana, Nevada, New Jersey, Oregon, South Dakota, Vermont, and Washington – have legalized recreational marijuana sales, but few research studies have measured exposure to secondhand marijuana smoke in everyday settings. We reviewed 729 papers on exposure to mari juana in the scientific literature, and we found almost no published papers measuring fine particle mass concentrations from secondhand cannabis smoke in homes. Both marijuana and tobacco cigarettes pro duce fine particle mass concentrations (PM2.5) consisting of airborne particles less than 2.5 μm in diameter. The PM2.5 ymax concentrations in the 9 Marlboro tobacco cigarette ex periments had a mean of 154 μg/m3 and ranged from 22 to 209 μg/m3. Each marijuana source produced a larger mean maximum concentration ymax than the tobacco cigarettes
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