Assessment of early kidney function biomarkers and environmental exposure to contaminant mixtures in Mexican brick-making workers under precarious labor conditions.

Artisanal brick-making exposes workers to mixtures of environmental contaminants under precarious conditions. This study assessed exposure to PAHs, arsenic, fluoride, lead, and their associations with early kidney damage biomarkers in 109 adults from three brick-making communities in central Mexico. Urinary and blood concentrations of contaminants were measured using validated analytical methods, and renal biomarkers (CYS-C, B2M, OPN, KIM-1, NGAL) were quantified via multiplex ELISA. Median urinary concentrations of 1-OH-PYR (1.3-2.3 µmol/mol uCr), arsenic (20.8-45.3 µg/L), and fluoride (1.6-2.6 mg/g uCr) exceeded reference values in a substantial proportion of participants. Cystatin-C and osteopontin showed significant associations with arsenic, fluoride, and PAH metabolites, including nonlinear relationships. No consistent associations were found for NGAL or KIM-1. These findings provide evidence of early renal alterations related to environmental exposures and support the utility of early-effect biomarkers for public health surveillance in vulnerable populations exposed to nephrotoxic mixtures under informal occupational conditions.