Associations Between Residential Indoor Environmental Indicators and Respiratory Allergic Symptoms Among Children in Shenzhen, China

Children are vulnerable to indoor environmental exposures, yet evidence from direct measurements in residential environments remains limited. This study included 115 observations from 74 children in Shenzhen during 2023–2024, with 111 observations available for regression-based analyses. Indoor environmental indicators were evaluated using single-indicator generalized estimating equation (GEE) models, restricted cubic spline (RCS) analyses, and weighted quantile sum (WQS) regression. The primary fully adjusted GEE models included age, sex, body mass index, family history of allergy, indoor temperature, district, and survey year. Asthma-related and allergic rhinitis-related symptoms were reported in 35.7% and 47.8% of the 115 observations, respectively. In the fully adjusted models, illuminance was nominally positively associated with both outcomes, whereas NO2 was nominally inversely associated with asthma-related symptoms. For allergic rhinitis-related symptoms, NH3 showed a nominal positive association, whereas O3 and total volatile organic compounds showed nominal inverse associations. However, none of these associations remained statistically significant after false discovery rate correction. Exploratory RCS analyses suggested potential nonlinear associations for several indicators. Exploratory WQS regression did not identify a significant overall mixture association. Overall, the associations were sensitive to adjustment and multiple-testing correction and should be considered exploratory. Longitudinal studies with repeated exposure measurements are needed to confirm these findings.