Prevalence and factors associated with self-reported exposure to secondhand cannabis smoke in the United States and Canada in 2019.

Little is known about exposure to secondhand cannabis smoke (SHCS) among residents of detached single-family homes and multiunit housing (MUH). Using data from the 2019 International Cannabis Policy Study, the prevalence of (a) self-reported exposure to SHCS at home (n = 33,024) and (b) self-reported SHCS incursions into MUH (defined as SHCS from another unit/the outdoors, n = 15,634) was estimated in (1) Canada; (2) US states where non-medical cannabis use was legal, and (3) US states where it remained illegal. Factors associated with exposures and incursions were assessed using weighted logistic regression. Overall, 16.9% of residents in Canada, 20.6% in US legal states, and 15.5% in US illegal states reported exposure to SHCS in their homes at least once in the previous month. One quarter (25.7%) of Canadian MUH residents, 26.6% from US legal states, and 20.1% from US illegal states reported at least monthly incursions. Sociodemographic factors associated with incursions suggested MUH residents reporting incursions lived in qualitatively different MUH than those not reporting incursions. Irrespective of the legality of non-medical cannabis use, smoke-free policies in MUH should protect residents from involuntary exposure to all types of secondhand smoke.