Association of self-reported asthma symptoms and allergic rhinoconjunctivitis with truck traffic frequency and environmental tobacco smoke exposure among preschool children in Gauteng townships, South Africa

This study aimed to investigate the association between self-reported asthma symptoms, allergic rhinoconjunctivitis, truck traffic frequency, and environmental tobacco smoke exposure among preschool children in Gauteng townships, South Africa. This cross-sectional study was conducted in 42 randomly selected preschools in Mabopane and Soshanguve, Gauteng Province, South Africa. A total of 1844 questionnaires were returned, of which 1840 were included after data cleaning. Associations between demographic, behavioural, and environmental factors and respiratory and allergic health outcomes were assessed using mixed-effects logistic regression models with a random intercept for preschool to account for clustering. The prevalence of self-reported asthma and wheeze ever was 6.8% and 15.4%, respectively. Allergic rhinoconjunctivitis was present in 8.6% of the total study population and in 8.9% of participants with a classifiable outcome. Environmental tobacco smoke (ETS) exposure at home was associated with higher odds of self-reported wheeze ever (AOR = 1.75; 95% CI: 1.20–2.55; p = 0.004) and allergic rhinoconjunctivitis (AOR = 1.65; 95% CI: 1.01–2.68; p = 0.044), but not self-reported asthma (AOR = 1.36; 95% CI: 0.81–2.27; p = 0.242). ETS exposure at preschool, transport, and restaurants showed no significant associations with any outcome. Truck traffic frequency associations were inconsistent across categories, with some inverse associations and no clear exposure-response pattern. Household ETS exposure was linked to wheeze ever and allergic rhinoconjunctivitis, but not asthma; truck traffic associations were inconsistent, with no clear exposure–response pattern.