Location and home rules of cannabis use - Findings from marijuana use and environmental survey 2020, a nationally representative survey in the United States.

Cannabis combustion and aerosolization may be associated with adverse health for users and nonusers through secondhand and thirdhand exposure. As cannabis regulation becomes more lenient, understanding where cannabis is used and whether homes have rules restricting use is needed. This study aimed to identify locations, presence of other people, and in-home rules of cannabis use in the United States (U.S.). This secondary analysis of 3,464 inhalation-based (smoking, vaping, dabbing) cannabis users in past 12 months drew from a cross-sectional probability-based online panel of 21,903 U.S. adults in early 2020, providing nationally representative estimates. We describe presence of other people and location at most recent use (smoking, vaping, dabbing, respectively). We also describe household restrictions on in-home cannabis smoking by cannabis smokers vs non-smokers, and by presence of children in home. Cannabis smoking, vaping, and dabbing most often occurred at users' own homes (65.7%, 56.8%, and 46.9%, respectively). More than 60% of smoking, vaping, and dabbing occurred with someone else present. About 68% of inhalation-based cannabis users (70% and 55%, smokers and non-smokers, respectively) did not have complete restrictions on in-home cannabis smoking; among them, over a quarter lived with children under 18. In the U.S., inhalation-based cannabis use most commonly occurs at home, with others present and a substantial proportion of users lacking complete in-home cannabis smoking restrictions, raising risks of secondhand and thirdhand smoke exposure. These circumstances demand residential interventions for developing bans on indoor cannabis smoking, especially around vulnerable children.