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

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.

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.

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).

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