Insights from human biomonitoring studies of children's exposure to indoor air pollutants in school and home environments: A systematic review

Human biomonitoring offers critical insight into the total internal dose of indoor air pollutants, yet standardised protocols for school-age population remain undefined. This review systematically evaluated biomarkers, biological matrices, and analytical strategies for assessing school-aged children's exposure to volatile (VOCs) and semi-volatile organic compounds (SVOCs) in home and school environments. A systematic search across four databases identified 79 peer-reviewed studies involving children aged 6–12. Data were synthesised to evaluate the performance of biomarkers relative to concurrent environmental monitoring data, with a focus on methodological applicability and study design heterogeneity. The analysis revealed a geographic bias toward high-income regions and a critical data gap regarding educational settings, with only 15% of studies investigating schools. Methodologically, urine emerged as the consensus biological matrix, though the utility of metabolites varies by half-live times. A key divergence was identified in exposure pathways: active air sampling effectively predicts the internal dose of VOCs, confirming inhalation as the primary pathway, while settled dust collection is a superior predictor for SVOCs, validating that accidental ingestion is dominant. Furthermore, clinical outcomes proved more sensitive than general oxidative stress markers for verifying the health risks of environmental tobacco smoke. Currently, cross-study comparisons are hindered by methodological fragmentation and predominant cross-sectional designs that fail to capture peak exposure activities. Future research must adopt a novel methodological framework that combines harmonised longitudinal biomonitoring with source-specific environmental sampling. This integrated approach is crucial for attributing pollutant sources and accurately characterising the health risks of children in the indoor environment. • Data is biased towards high-income regions, and only 15% of studies assessed schools • Inconsistent sampling protocols hinder global cross-study comparisons • Inhalation dominates for VOCs exposure, whereas dust ingestion drives SVOC exposure • Urine is a consensus biological matrix, but sampling timing requires standardisation • A novel framework is needed to combine biomonitoring with source-specific sampling