Influence of Cannabis Cultivation on Outdoor Air Quality: Meteorological Drivers in Urban VOC-Limited Regimes

Cannabis cultivation is a source of biogenic volatile organic compounds (BVOCs), which can contribute to ozone (O3) formation and growth of ultrafine particles (UFPs; <100 nm). This study used mobile monitoring to evaluate outdoor air quality near a large (440,000 m2) commercial cannabis cultivation facility (CCF) in Delta, BC, Canada. Measurements of O3 and UFPs were collected during summer under peak photochemical conditions at urban and Rural upwind and downwind locations and also on roads directly surrounding the greenhouses. Dispersion modeling (CALPUFF v7.2.1) was used to estimate the BVOC concentrations. Median O3 was enhanced by 3 ppb at the downwind Urban area of the CCF. UFP concentrations increased by 700% in the greenhouse area when wind transported urban NOx emissions toward the CCF. Conversely, UFPs decreased in the Urban area when downwind of the facility, suggesting enhanced formation of more volatile products under high-NOx conditions. Our results indicate that large CCFs should be preferentially sited in Rural areas rather than near urban centers in order to avoid an increase in tropospheric O3 concentrations. Future mobile monitoring with real-time VOC observations and boundary layer characterization would improve attribution of secondary pollutant formation near cannabis facilities.