Longitudinal Nephrotoxic Metal Exposure in a Cohort of Farm Workers in Sonora (December 2025)-Longitudinal Nephrotoxic Metal Exposure in a Cohort of Farm Workers in Sonora

Longitudinal Nephrotoxic Metal Exposure in a Cohort of Farm Workers in Sonora

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This study investigates longitudinal exposure to nephrotoxic metals among male agricultural workers in Sonora, Mexico, comparing their metal(loid) urinary concentrations to office workers and other populations. Given global concerns about rising chronic kidney disease (CKD) among outdoor workers, potentially linked to exposure to metals such as arsenic (As), cadmium (Cd), lead (Pb), nickel (Ni), chromium (Cr), mercury (Hg), and uranium (U), this study addresses an understudied population near the US-Mexico border.<br /><br />Methods involved collecting first-morning urine samples at the start (spring) and end (summer) of the grape harvest season in 2019 from 77 agricultural workers and 21 office workers. Urine was analyzed for metal(loid) concentrations using inductively coupled plasma-mass spectrometry (ICP-MS), adjusted for specific gravity and creatinine to account for hydration status.<br /><br />Findings revealed that agricultural workers had significantly higher urinary levels of As, Pb, Ni, and U compared to office workers. Notably, uranium levels increased over the work season, possibly reflecting exposure to regional uranium deposits and occupational dust inhalation, while As, Pb, and Ni levels decreased over time. Urinary Cd levels in farmworkers were similar to levels reported in agricultural populations from Guatemala and Nicaragua, but As and U levels were higher than in these groups and substantially above Mexican American populations from NHANES data. Regression analysis showed that farmworker occupation was associated with higher As levels, and residence in Puebla was linked to elevated Cd, Pb, and Ni.<br /><br />The study's strengths include its longitudinal design, controlling for potential confounders by recruiting from a single farm with shared housing, meals, and water, and the use of first-morning void samples. Limitations include a small, male-only cohort restricting generalizability, lack of environmental samples preventing source apportionment, and analysis of total rather than species-specific metals.<br /><br />Conclusions emphasize the elevated metal(loid) exposures among Mexican agricultural workers relative to office workers and US populations, underscoring the need for further research to identify exposure sources and health impacts. Future work should incorporate additional biomarkers, environmental sampling, and explore interventions such as water filtration and personal protective equipment. Policy recommendations include establishing nationwide metal(loid) exposure surveillance in Mexico to inform regulation and public health interventions aimed at reducing CKD risk in this vulnerable occupational group.

Keywords

nephrotoxic metals

agricultural workers

Sonora Mexico

urinary metal concentrations

chronic kidney disease

arsenic exposure

uranium exposure

longitudinal study

occupational health

metal exposure surveillance