Abstract
INTRODUCTION: Tobacco smoke exposure (TSE) among individuals who do not smoke has declined in the USA, however, gaps remain in understanding how TSE patterns across indoor venues-including in homes, cars, workplaces, hospitality venues, and other areas-contribute to TSE disparities by income level. METHODS: We obtained data on adults (ages 18+, N=9909) and adolescents (ages 12-17, N=2065) who do not smoke from the National Health and Nutrition Examination Survey, 2013-2018. We examined the prevalence of self-reported, venue-specific TSE in each sample, stratified by poverty income ratio (PIR) quartile. We used linear regression models with a log-transformed outcome variable to explore associations between self-reported TSE and serum cotinine. We further explored the probability of detectable cotinine among individuals who reported no recent TSE, stratified by PIR. RESULTS: Self-reported TSE was highest in cars (prevalence=6.2% among adults, 14.2% among adolescents). TSE in own homes was the most strongly associated with differences in log cotinine levels (β for adults=1.92, 95% CI=1.52 to 2.31; β for adolescents=2.37 95% CI=2.07 to 2.66), and the association between home exposure and cotinine among adults was most pronounced in the lowest PIR quartile. There was an income gradient with regard to the probability of detectable cotinine among both adults and adolescents who did not report recent TSE. CONCLUSIONS: Homes and vehicles remain priority venues for addressing persistent TSE among individuals who do not smoke in the USA. TSE survey measures may have differential validity across population subgroups.