Low-level cadmium exposure in Toyama City and its surroundings in Toyama prefecture, Japan, with references to possible contribution of shellfish intake to increase urinary cadmium levels

Objectives: This study was initiated to examine if exposure to cadmium (Cd) was high also outside of the previously identified Itai-itai disease endemic region in the Jinzu River basin in Toyama prefecture in Japan. Methods: Morning spot urine samples were collected in June–August 2004 from 651 adult women (including 535 neversmokers) in various regions in Toyama prefecture, and subjected to urinalyses for cadmium (Cd), a1-microglobulin (a1-MG), h2-microglobulin (h2-MG), N-acetyl-h-d-glucosaminidase (NAG), specific gravity (SG or sg) and creatinine (CR or cr). Three months later, the second urine samples were collected from those with elevated Cd in urine (e.g., R4 Ag/g cr), together with answers to questionnaires on shellfish consumption. Results: The geometric mean (GM) Cd, a1-MG, h2-MG and NAG (after correction for CR) for the total participants were 2.0 Ag/g cr, 2.4 mg/g cr, 104 Ag/g cr and 2.8 units/g cr, respectively; further analysis with never-smoking cases only did not induce significant changes in these parameters. Analyses of the second urine samples from the high Cd subjects showed that there was substantial decrease (to about a half) in Cd in the 3-month period, and that the decrease was accompanied by reduction in a1- MG and NAG (h2-MG did not show elevation even in the first samples). The urinalysis results in combination with the results of the questionnaire survey suggest that the high urinary Cd was temporary and might be induced by intake of shellfish that is edible whole. Conclusions: The overall findings appear to suggest that Cd exposure in Toyama populations (outside of the Itai-itai disease endemic region) was at the levels commonly observed on the coast of the Sea of Japan, and that the Cd level in urine might be modified by the intake of some types of seafood. Further studies are necessary to elucidate the relation of urinary Cd with seafood intake.