Associations between multi-metal joint exposure and decreased estimated glomerular filtration rate (eGFR) in solar greenhouse workers: A study of a unique farmer group.

BACKGROUND

Solar greenhouse workers, a unique farmer group, have been reported to have a higher risk of chronic kidney disease (CKD) compared to the general population, possible due to exposure to multiple metals.

OBJECTIVE

This study aimed to investigate the associations between exposure to multiple metals and the estimated glomerular filtration rate (eGFR).

METHODS

A cross-sectional study was conducted in the Northwest China. Urine samples were tested for concentration of 14 metals, including chromium, manganese, iron et al. Blood creatinine was measured to calculate eGFR, which was to evaluate the kidney function. Linear model and the Bayesian Kernel Machine Regression (BKMR) models were used to evaluate the associations between metals exposure and eGFR.

RESULT: The study included 281 solar greenhouse workers, with 128 (45.6%) males and 153 (54.4%) females. The highest median concentrations of metals were zinc (418.55 μg/L), strontium (368.77 μg/L), and iron (55.73 μg/L), respectively. The linear model analysis showed that urinary levels of copper and zinc were negatively associated with eGFR [β = -0.021, 95% CI (-0.048, -0.007); β = -0.018, 95% CI (-0.068, -0.005)] considering a false discovery rate. BKMR results indicated a significant overall negative effect of 14 metals exposure on the eGFR when all metal levels were above the 50th percentile compared to the median value.

CONCLUSIONS

The decrease in eGFR among solar greenhouse workers was related to mixed metal exposure. Reducing exposure to the metals of copper, zinc, and lead could effectively protects kidney function. Further prospective studies are needed to resolve concerns about reverse causality.