A Comparison of the Nephrotoxicity of Low Doses of Cadmium and Lead

Abstract

Environmental exposure to moderate-to-high levels of cadmium (Cd) and lead (Pb) is associated with nephrotoxicity. In comparison, the health impacts of chronic low-level exposure to Cd and Pb remain controversial. The aim of this study was to therefore evaluate kidney dysfunction associated with chronic low-level exposure to Cd and Pb in a population of residents in Bangkok, Thailand. The mean age and the estimated glomerular filtration rate (eGFR) for 392 participants (195 men and 197 women) were 34.9 years and 104 mL/min/1.73 m², respectively, while the geometric mean concentrations of urinary Cd and Pb were 0.25 μg/L (0.45 μg/g of creatinine) and 0.89 μg/L (1.52 μg/g of creatinine), respectively. In a multivariable regression analysis, the eGFR varied inversely with blood urea nitrogen in both men (β = -0.125, p = 0.044) and women (β = -0.170, p = 0.008), while inverse associations of the eGFR with urinary Cd (β = -0.132, p = 0.043) and urinary Pb (β = -0.130, p = 0.044) were seen only in women. An increased urinary level of Cd to the median level of 0.38 μg/L (0.44 μg/g of creatinine) was associated with a decrease in the eGFR by 4.94 mL/min/1.73 m² (p = 0.011). The prevalence odds of a reduced eGFR rose 2.5-, 2.9- and 2.3-fold in the urinary Cd quartile 3 (p = 0.013), the urinary Cd quartile 4 (p = 0.008), and the urinary Pb quartile 4 (p = 0.039), respectively. This study suggests that chronic exposure to low-level Cd is associated with a decline in kidney function and that women may be more susceptible than men to nephrotoxicity due to an elevated intake of Cd and Pb.

Keywords: cadmium; creatinine clearance; creatinine excretion; glomerular filtration rate; lead; nephrotoxicity.

Figure 1

Comparing effects of cadmium and lead on eGFR change. The scatterplots show the relationship between the eGFR and log [excretion of Cd (E_Cd)/creatinine clearance (C_cr)) × 10⁵] and between the eGFR and log [excretion of Pb (E_Pb)/C_cr) × 10⁵] in all subjects (A,B). The linear equations and coefficients of determination (R²) are provided together with standardized β and p-values. The bars represent the mean values for the eGFR across urinary Cd and urinary Pb quartiles (C,D) with adjustments for various covariates and potential interactions. The numbers of subjects are provided for all subgroups. The geometric mean (GM) values (standard deviation) for E_Cd/C_cr × 100 in urinary Cd quartiles 1, 2, 3 and 4 were 0.12 (0.05), 0.30 (0.05), 0.48 (0.07) and 0.88 (0.44) µg/L, respectively. The GM (SD) for E_Pb/C_cr × 100 in urinary Pb quartiles 1, 2, 3 and 4 are 0.41 (0.36), 1.26 (0.10), 1.63 (0.14) and 2.73 (2.86) µg/L, respectively.