UCSF

Introduction: Cannabis regulation and use are undergoing dramatic changes. New cannabis products and new ways of using are emerging.  These changes have the potential to affect exposure to cannabis smoke and other emissions from cannabis use.  Cannabis smoke is known to contain fine, respirable particles (PM_2.5) and other toxicants and carcinogens. 

Objectives: To assess the potential for exposure to PM2.5 from novel cannabis aerosols, we measured PM_2.5 concentrations in a cannabis retail outlet (a dispensary) that permits on-site consumption of cannabis via non-combustion methods including vaporization and dabbing.

Methods: PM2.5 concentrations in the dispensary were measured around the clock for five weeks using 2 laser photometer instruments (429,604 data points collected over 38.69 days).  The instruments were calibrated gravimetrically using a controlled cigarette generation system at regular intervals during the experiment. Outdoor PM_2.5 concentrations were taken from a nearby EPA monitoring station.

Results: The average PM_2.5 concentration in the dispensary retail space, during business hours, was 84 ± 124 µg/m³, with a median of 47 µg/m³.  The average PM_2.5 concentration when the business was closed was 3 ± 7 µg/m³ with a median of 2 µg/m³.   The highest daily concentrations correlated with the hours with the most customers.

Conclusion: Our results suggest that the use of cannabis products indoors, even by non-combustion methods, increases the concentration of PM_2.5. These findings are of concern to the public health because the business studied was in compliance with local laws and because PM_2.5 exposure is a known cause of cardiopulmonary and metabolic disease.