In Ontario, 7.5% of the population reported being exposed to cannabis smoke in their residences prior to the legalization of recreational cannabis in Canada in 2018. Similarly, 6.6% of Ontarians reported exposure to tobacco smoke over the same time period. These results provide an understanding of the demographic factors that put individuals at higher risk of exposure to ETS and ECS. Without taking housing type into account, we found that individuals exposed to ECS differed significantly from those not exposed in terms of marital status, household income, past 12 month cannabis use, and never use of cigarettes. However, within MUH, these demographic factors were no longer predictive of ECS exposure, indicating that the predictors of exposure are those associated with living in MUH. These results suggest that all individuals living in MUH are at risk of ECS exposure, regardless of demographic factors. It follows that the primary point of intervention should be policies aimed at reducing cannabis smoking inside MUH. This can be accomplished through targeted education campaigns to raise awareness of the health risks of exposure; and by encouraging and supporting the adoption of smoke-free housing policies at municipal and provincial levels. Smoke-free policies in MUH may also support cessation behavior, including reducing smoking and increasing quit attempts among residents who smoke [16,17].

Past year cannabis use was strongly associated with ECS within MUH. It is possible that individuals who are cannabis smokers may be better able to detect ECS compared to individuals who are not familiar with its odor. It is also possible that there is a clustering of cannabis users, whereby individuals who smoke cannabis are more likely to live in MUH where other cannabis users live. The variances between those reporting exposure to ECS and ETS in MUH suggests that there may be a systematic difference in the individuals who are at risk of ECS or ETS—either in the factors which cause individuals to self-report exposure or in the type of MUH in which they reside. Past year cannabis users also had a higher odds of reporting both ETS and ECS, but never smokers only had a higher odds of reporting ETS. It is possible that past year tobacco users are more able to identify cannabis as distinct from tobacco smoke, whereas never smokers are unable to detect the difference between tobacco and cannabis use due to a lack of experience. These hypotheses should be explored in more detail in future research but suggest that self-report measures may underestimate the extent of exposure to both ETC and ECS.

Interestingly, the demographic factors related to ECS were different than those associated with ETS. Within MUH, older age and being male was significantly associated with lower odds of ETS, but not with ECS. A similar study of self-reported involuntary ETS exposure in MUH also found lower odds of exposure amongst males and older individuals [15], Moreover, having never been married was strongly associated with ETS, but not with ECS.

This study is subject to a number of limitations. The CAMH Monitor uses RDD, which inherently excludes individuals without a phone number. There may be a systematic difference in the individuals who are choosing to report, thus this study may be subject to response bias. This measure only asks about ETS and ECS from adjacent neighboring units or outside of the building and does not include other important exposure environments such as within the household, at work, or outside the home.

This study uses the definition of involuntary exposure to ETS and ECS from sources outside the home (e.g., from a neighboring unit) because this is relevant to public health and important for the development of smoke-free policy regulations in MUH. The issue of secondhand exposure from smoking that occurs inside the home is an important source of exposure for children and other individuals living in the home. Consequently, the estimates here underestimate the total burden of environmental smoke. The focus of this paper is with the narrow definition used for regulatory policy. Studies that measure air quality and cannabis smoking behavior in different environments and dwelling types will increase our understanding of exposure. Measuring exposures in children living in MUH is also an important avenue of research. With the growing use of cannabis, monitoring the prevalence of ECS and ETS in MUH is needed to fully understand the extent of involuntary exposures within an evolving policy and regulation landscape.