Renal Function after Reduction in Cadmium Exposure: An 8-Year Follow-up of Residents in Cadmium-Polluted Areas

Background and Objective: Long-term exposure to cadmium (Cd) causes renal dysfunction, but the change in renal function with exposure is unknown. We assessed the evolution of Cd-induced renal effects after a reduction in dietary exposure to Cd in rice. Methods: Four hundred twelve residents in previously Cd-polluted and nonpolluted areas were examined twice, in 1998 and in 2006. Changes in blood Cd, urinary Cd, and kidney function [N-acetyl-β-D-glucosaminidase (NAG), β₂-microglobulin, and albumin in urine] were measured. Results: In the most polluted area, mean blood Cd was 8.9 μg/L and 3.3 μg/L in 1998 and in 2006, respectively, and urinary Cd was 11.6 and 9.0 μg/g creatinine. Urinary albumin in 1998 increased with urinary Cd, but no such exposure-response relation appeared for 2006 albumin versus urinary Cd 1998, indicating recovery. Other biomarkers of kidney function were also elevated in 1998. Partial recovery was observed for NAG among women and was suggested for β₂-microglobulin among young individuals. The probability of having β₂-microglobulin levels above the 95th percentile in 2006 was high in those with elevated β₂ -microglobulin in 1998 [odds ratio (OR) = 24.8; 95% confidence interval (CI): 11.2, 55.3] compared with albumin (OR = 3.0; 95% CI: 1.2, 7.5) and NAG (OR = 2.6; 95% CI: 1.6, 4.4). Conclusions: Results suggest that a Cd-mediated increase in urinary albumin excretion is reversible upon substantial reduction of exposure. For markers of tubular effects, we observed a tendency toward improvement but not complete recovery. Data from repeated observations suggest that β₂-microglobulin may be more informative than NAG as an indicator for an individual's future tubular function.