Smoke-Free Laws and Disparities in Secondhand Smoke Exposure Among Nonsmoking Adults in the United States, 1999-2014.

Abstract

Little is known about the relationship between smoke-free laws and persistent disparities in secondhand smoke (SHS) exposure among nonsmoking adults in the United States. We constructed time-varying smoke-free law measures representing whether or not at least 50% of each US county's population was covered by smoke-free laws in workplaces and hospitality venues (restaurants/bars). We merged these data with restricted data on cotinine-derived SHS exposure among nonsmokers from the National Health and Nutrition Examination Survey, 1999-2014 (N = 25 444). Using logistic regression, we estimated associations between smoke-free law coverage and SHS exposure among all nonsmokers, and within age strata (25-39, 40-59, 60+). We explored differential associations by gender, race/ethnicity, education, and poverty-income ratio (PIR) by testing the significance of interactions terms for the full sample and within age strata. In adjusted models, hospitality coverage was associated with lower odds of SHS exposure in the full sample (odds ratio [OR] = 0.62; 95% confidence interval [CI] = 0.51-0.76), and within each age group, with ORs ranging from 0.58 (ages 25-39) to 0.67 (ages 60+). Workplace coverage was associated with lower SHS exposure only among younger adults (OR = 0.81; 95% CI = 0.65-0.99). Within the full sample and among adults ages 40-59, hospitality laws were associated with narrowing SHS exposure differentials between males and females. Among adults ages 40-59, workplace laws were associated with narrowing exposure differentials between males and females, but worsening exposure disparities by PIR. Smoke-free laws may reduce SHS exposure among adult nonsmokers, but may be insufficient to improve disparities in SHS exposure. In a repeated cross-sectional sample of adult nonsmokers, smoke-free laws in hospitality venues were consistently associated with lower odds of SHS exposure and appeared to narrow exposure differentials between males and females. Associations between workplace smoke-free laws and SHS exposure were variable by age. Among adults ages 40-59, workplace laws were associated with narrowing exposure differentials between males and females while exacerbating exposure differentials by PIR. Differential patterns of association highlight the need to examine the impacts of tobacco control policies on downstream health equity.