Associations of Heat Exposure with Acute Kidney Injury and Kidney Function in Mexican Agricultural Workers

Agricultural workers endure physically demanding, high heat work daily, increasing the risk of kidney injury and reduced kidney function. However, few studies have examined individual measures of heat exposure and risk of kidney injury and impaired function. We assessed the association between measures of heat exposure with acute kidney injury and kidney functioning among agricultural workers, compared to a group of office workers in the same region.

We recruited 77 adult males working in agriculture and 21 adult males in office jobs in Sonora, Mexico in 2019. We administered a demographic questionnaire to participants. A proxy physiological strain index (PSI), based on point measurements of heart rate and tympanic temperature, was used to estimate individual heat exposure. Kidney function was measured using the estimated glomerular filtration rate (eGFR). Kidney injury was assessed via urinary neutrophil gelatinase-associated lipocalin (uNGAL). We compared uNGAL and eGFR over time in the two study groups. We assessed proxy PSI associations with uNGAL and eGFR using linear mixed-effects models, adjusting for age, body mass index, and urinary specific gravity factor.

We observed statistically significant differences between agricultural and office workers for eGFR (GM: 121.85 vs. 115.66 mL/min/1.73 m², p = .04). Among agricultural workers, creatinine-adjusted uNGAL levels rose in summer compared to spring (GM: 4.47 vs. 1.98 mg/g creatinine, p < .01), and eGFR declined during the same period GM:(108.41 vs. 122.38 mL/min/1.73 m², p < .01). In mixed models, proxy PSI was inversely associated with eGFR (β-coefficient:-2.87, 95% CI: -4.02, -1.72).

Season and proxy PSI predicted kidney functioning in agricultural workers in this study. As climate warming continues, high-risk occupational groups such as agricultural workers will face increasing heat-related health risks.