Air Pollution Exposure and Gut Microbiota-Related Biomarkers in Healthy School-Age Children: A Biomonitoring Study

The aim of the study was to investigate the relationship between air pollution exposure and gut microbiota-related biomarkers among a cohort of healthy school-age children. A cross-sectional biomonitoring study was conducted among 11-year-old healthy children living in central Italy. Selected urinary (u) volatile organic compounds (VOCs) (benzene, toluene, ethylbenzene, xylenes, methyl tertbutyl ether, ethyl tert-butyl ether, 2-methyl-2- butyl methyl ether, and diisopropyl ether) were measured as exposure biomarkers while u-indican and faecal (f) zonulin were assessed as indicators of gut dysbiosis and intestinal permeability, respectively. Socio-demographic and lifestyle data were collected through questionnaires. u-VOCs showed higher geometric means among children exposed to environmental tobacco smoke, living in urban areas, and those spending a longer time in motor vehicles. u-Ethylbenzene and u-toluene were the most abundant compounds (mean ± SD: 307 ± 118 ng/L and 188 ± 94 ng/L, respectively). Mean f-zonulin and mean u-indican were, respectively, 49.09 ± 18.41 ng/mL and 5.97 ± 3.50 mg/dL. A statistically significant positive correlation was observed between u-ethylbenzene and u-indican (p = 0.02) and between u-toluene and f-zonulin (p = 0.05). These findings provide preliminary evidence that air pollution may influence gut microbial metabolic activity and intestinal barrier regulation in children, supporting the need for larger longitudinal studies.