Environmental and Health Characterization of the Upper Atoyac River Basin, Puebla–Tlaxcala, Mexico

The Upper Atoyac River Basin (UARB), located in Puebla and Tlaxcala, Mexico, is one of the most environmentally and health-impacted regions in the country. Over recent decades, chronic non-communicable diseases—particularly childhood leukemia and chronic kidney disease—have increased markedly, in association with exposure to complex mixtures of industrial and agricultural contaminants. This cross-sectional study assessed environmental exposures and associated biological effects in adolescents from five UARB communities representing different levels of industrialization. Blood, urine, and urban dust samples were analyzed for metals and metalloids (ICP-MS), polychlorinated biphenyls (PCBs), and organochlorine (OC) and organophosphate (OP) pesticides (GC-MS). In a subgroup, inflammatory cytokines were quantified by flow cytometry. Data were integrated using principal component analysis (PCA) and generalized linear models (GLMs) adjusted for age, sex, body mass index, and community. Results showed widespread exposure to PCBs, OCs, and metals, with heterogeneous patterns across sites. Enrichment factors in urban dust identified As, Sb, and Pb as clear markers of anthropogenic origin. Exposure components dominated by PCBs and OCs were associated with elevated hepatic and hormonal markers, whereas those dominated by metals were correlated with lipid and endocrine alterations. Cytokine profiles revealed a proinflammatory pattern (IL-12, IFN-γ, IL-1β, IL-6, IL-17, IL-23) associated with dioxin-like PCBs and OCs, and a modulatory/epithelial pattern (IL-33, IL-18, IL-10) negatively correlated with metals, suggesting immunosuppression. These findings support a territorial exposure framework, in which adolescents in the UARB are continuously exposed to complex contaminant mixtures arising from industrial, environmental, and everyday settings, resulting in early systemic biological alterations despite being apparently healthy.