Assessment, detection, and validation of clinical associations of thirdhand smoke exposure (ADVOCATE) study protocol.

Background: Thirdhand smoke (THS) pollution is the residue of secondhand smoke (SHS) remaining in homes long after active smoking has ceased. This study is the first to characterize the clinical correlates of THS exposure (THSe) in children independent of secondhand smoke exposure (SHSe). The prevalence, sociodemographic characteristics, tobacco smoke exposure patterns, sources, clinical, and biomarker effects associated with THSe will be examined.

Method: Smoking and nonsmoking parents and their 0-11-year-olds (N = 1013) were recruited. Children were categorized into tobacco smoke exposure (TSE) groups via biochemical validation with salivary cotinine and hand nicotine: (1) no exposure group (NEG); (2) THSe-only group (TEG); and (3) Mixed SHSe and THSe group (MEG). At enrollment, 6-weeks, and 6-months, parental assessments and children's biological and home samples were obtained and analyzed for SHSe, THSe, THS pollution, inflammatory and oxidative stress markers.

Results: The mean (SD) child age was 5.8 (3.4) years; 50.7% were female; and 97% were non-Hispanic (97.0%); 67.5% were White, 25.7% were Black, 6.8% were Other/unknown race. In total, 57.9%, 18.2%, and 21.9% were classified in the NEG, TEG, and MEG, respectively. Sample and data analyses are ongoing.

Conclusion: This project will provide unique insights into how THSe in the absence of SHSe affects the clinical, inflammatory, and oxidative responses in children.

Impact: This is the first prospective longitudinal study to examine the prevalence of thirdhand smoke exposure in children of nonsmokers. Unlike prior tobacco smoke exposure research, this study will examine the contribution of thirdhand smoke exposure to pediatric health outcomes. Results will provide unique insights into how thirdhand smoke exposure in the absence of secondhand smoke exposure affects the clinical, inflammatory, and oxidative responses in children of nonsmokers.