A longitudinal study on urinary cadmium and renal tubular protein excretion of nickel-cadmium battery workers after cessation of cadmium exposure

Abstract

Purpose: This study aimed to predict the outcome of urinary cadmium (Cd) excretion and renal tubular function by analyzing their evolution through 10 years after Cd exposure ceased.

Methods: Forty-one female, non-smoking workers were recruited from the year 2004 to 2009 when being removed from a nickel-cadmium battery factory, and they were asked to provide morning urine samples on three consecutive days at enrollment and in every follow-up year until 2014. Urinary Cd and renal tubular function biomarkers including urinary β2-microglobulin (β2-m) and retinol-binding protein (RBP) concentrations were determined with the graphite furnace atomic absorption spectrometry and the enzyme-linked immunosorbent assays, respectively.

Results: The medians of baseline Cd, β2-m and RBP concentrations at enrollment were 6.19, 105.38 and 71.84 μg/g creatinine, respectively. Urinary β2-m and RBP concentrations were both related to Cd concentrations over the years (β absolute-β2-m = 9.16, P = 0.008 and β absolute-RBP = 6.42, P < 0.001, respectively). Cd, β2-m and RBP concentrations in the follow-up years were all associated with their baseline concentrations (β absolute-Cd = 0.61, P < 0.001; β absolute-β2-m = 0.64, P < 0.001; and β absolute-RBP = 0.60, P < 0.001, respectively), and showed a decreasing tendency with the number of elapsed years relative to their baseline concentrations (β relative-Cd = -0.20, P = 0.010; β relative-β2-m = -17.19, P = 0.002; and β relative-RBP = -10.66, P < 0.001, respectively).

Conclusions: Urinary Cd might eventually decrease to the general population level, and Cd-related tubular function would improve under the baseline conditions of this cohort.

Keywords: Cadmium; Exposure cessation; Repeated measurement; Retinol-binding protein; β2-Microglobulin.