Abstract Early-life exposure to environmental pollutants poses a critical risk to pediatric health, yet few studies have integrated chemical contaminants with urban land-use characteristics to assess their combined associations with the developing gut microbiome. In this study, we evaluated the associations between fecal heavy metal (HM) concentrations and residential land-use cover area (measured as area-based metrics within specific buffers), as well as gut microbial composition and predicted functional pathways, in 78 preschool children from the greater Taipei area. Using Bayesian kernel machine regression (BKMR), we characterized nonlinear and interactive exposure-response relationships. Elevated fecal cadmium (Cd) levels were significantly and positively associated with increased abundance of Bacteroides (q = 0.02), while nominal positive associations were observed with Klebsiella and Veillonella. Fecal lead (Pb) showed a suggestive positive association with Phocaeicola (q = 0.07). Crucially, residential land-use features modified these associations: increased gas station coverage was linked to lower Bacteroides and Veillonella levels but higher Klebsiella abundance, whereas green-space coverage was positively associated with Veillonella. The BKMR model highlighted synergistic negative associations between fecal Cd and gas station area coverage within a 1500-m residential buffer on Veillonella and Bacteroides, suggesting that the spatial distribution of physical urban infrastructure may be linked to the apparent effects of chemical contaminants on the gut microbiota. These environmental contaminants were further associated with alterations in predicted microbial functional pathways involved in energy metabolism, secondary metabolite biosynthesis, and genetic information processing. These findings suggest that children’s gut health may be associated with a complex interplay of urban chemical and structural factors. Our results underscore the need for science-informed urban management and health-protective zoning, which may inform strategies such as optimizing land-use cover area of gas stations near residential areas and increasing urban greenery to mitigate environmental risks during critical developmental windows.
Kao et al. (Fri,) studied this question.