Background: Two forms of environmental tobacco smoke (ETS) exposure have been described: second-hand smoke (SHS), which is the direct exposure to tobacco smoke; and third-hand smoke (THS), which is the exposure to residuals from tobacco smoke after the cigarette has been extinguished. The effects of SHS exposure on children’s respiratory health are known, but not of THS exposure. We evaluated the association between both exposures and respiratory complaints in children aged 0-13 years, and assessed whether the risk of respiratory complaints due to these exposures was higher in children with genetic predisposition for asthma compared to those without.
Methods: A cross-sectional survey (91 items) was performed in 10,000 families with a child aged 0-13 years living in South-Limburg, the Netherlands, assessing child and family characteristics, child’s respiratory health, and parental smoking behaviour. Data were analyzed with (adjusted) multiple logistic regressions.
Results: 1899 families responded. SHS exposure was not associated with an increased risk of respiratory complaints in children. THS exposure was associated with respiratory tract infections in the past 12 months (ORadjusted: 2.13; 95% CI: 1.04-4.36; p=0.04) and recent wheezing (ORadjusted: 2.61; 95%CI: 1.19-5.71; p=0.02) in children. There was no interaction between genetic predisposition for asthma and ETS exposure.
Conclusions: Unlike previous studies, our study could not reveal a significant association between SHS exposure and an increased risk of respiratory complaints in children, most likely due to study limitations concerning cross-sectional design, response rate, selection bias and parental underreporting of SHS exposure to their children. THS exposure was significantly associated with an increased risk of respiratory complaints in children. This adds to the limited knowledge about the health effects of THS exposure in children and suggests that more research on this topic is needed. A genetic predisposition for asthma combined with ETS exposure did not increase the risk of respiratory complaints in children.