UCSF

To assess the exposure of patrons and workers to secondhand cannabis smoke in the smoking lounge of a cannabis store, we measured airborne PM_2.5, cannabinoids, and nicotine in a cannabis store and a nearby coffee shop. PM_2.5 concentration was measured with laser photometers. PM_2.5 samples were collected on filters and cannabinoids were quantified by liquid chromatography with tandem mass spectroscopy and nicotine was quantified by gas chromatography. Activity and demographic data were recorded. The average PM_2.5 concentration over nine experiments conducted between September 2018 and August 2019 was 840 (standard deviation of 674 µg/m³). Concentrations of THC, CBD, and CBN in the particulate matter averaged 79.0 µg/m³, 0.708 ng/m³, and 8.60 ng/m³, respectively. Nicotine concentrations were below the level of quantification. Although a variety of consumption methods were observed, 91% of the observed consumption events were smoking. The business installed a ventilation system halfway through our study.  Before the ventilation system was installed, the average PM_2.5 was 905 µg/m³, afterwards it was 795 µg/m³.  This 12.2% decrease was not statistically significant.  Our results show that smoking cannabis indoors can create high concentrations of particulate air pollution that are known to cause adverse health effects.