Background: Exposure to secondhand smoke (SHS) from burning tobacco causes disease and death in nonsmoking children and adults. No risk-free level of SHS exposure exists. Methods: National Health and Nutrition Examination Survey (NHANES) data from 1999–2012 were used to examine SHS exposure among the nonsmoking population aged ≥3 years. SHS exposure among nonsmokers was defined as a serum cotinine level (a metabolite of nicotine) of 0.05–10 ng/mL. SHS exposure was assessed overall and by age, sex, race/ethnicity, poverty level, education, and whether the respondent owned or rented their housing. Results: Prevalence of SHS exposure in nonsmokers declined from 52.5% during 1999–2000 to 25.3% during 2011–2012. During this period, declines were observed for all population subgroups, but disparities exist. During 2011–2012, SHS was highest among: children aged 3–11 years (40.6%), non-Hispanic blacks (46.8%), persons living below the poverty level (43.2%), and persons living in rental housing (36.8%). Among children aged 3–11 years, 67.9% of non-Hispanic blacks were exposed to SHS compared with 37.2% of non-Hispanic whites and 29.9% of Mexican Americans. Conclusion: Overall, SHS exposure in the United States has been reduced by half since 1999–2000. However, 58 million persons were still exposed to SHS during 2011–2012, and exposure remains higher among children, non-Hispanic blacks, those living in poverty, and those who rent their housing. Implications for Public Health Practice: Eliminating smoking in indoor spaces fully protects nonsmokers from SHS exposure; separating smokers from nonsmokers, cleaning the air and ventilating buildings cannot completely eliminate exposure. Continued efforts to promote implementation of comprehensive statewide laws prohibiting smoking in workplaces and public places, smoke-free policies in multiunit housing, and voluntary smoke-free home and vehicle rules are critical to protect nonsmokers from this preventable health hazard in the places they live, work, and gather. © 2015, Department of Health and Human Services. All rights reserved.
