Spatial Distribution of Organochlorine Pesticide Serum Concentrations in Mexican Children and Adolescents Living in and Out the Polluted Atoyac Watershed Basin.

The Atoyac river basin is one of the most polluted watershed basins in Mexico. Recent studies have reported the presence of organochlorine pesticides (OCPs) in this highly urbanized region through environmental monitoring, raising concerns about potential health risks, particularly for children and adolescents. We still lack information about its human exposure through biological samples that represent a more realistic measure of OCPs body burden. To evaluate, we compared the serum concentrations of OCPs in children and adolescents living within and outside the Atoyac watershed basin. We included 428 individuals under 20 years old who participated as controls in a population-based study conducted in three central-southern Mexican states (2021-2024). We collected sociodemographic characteristics through face-to-face interviews and obtained serum samples in which we quantified 24 OCPs by gas chromatography. To georeference, we classified the participants as living within or outside the Atoyac basin and compared their respective serum concentrations for those OCPs detected over 10% of samples. We found two heterogeneous spatial distribution patterns of OCPs serum concentrations. HCB, dieldrin, oxychlordane, and endosulfan sulfate were higher in the Atoyac basin, with the two formers being statistically significant. In contrast, p,p'-DDE was significantly higher outside the Atoyac basin. The two patterns of exposure between the two regions emphasized one pattern driven by industry and agriculture, and the second driven by vector-borne disease control. It reinforces the need for regulation and increased monitoring in the Atoyac river basin to provide information about adverse health effects in children and adolescents.