A Follow-up Study on Renal Tubular Dysfunction in Women Living in the Cadmium-polluted Jinzu River Basin in Toyama, Japan

A follow-up study on renal tubular dysfunction was carried out on 193 female inhabitants of the cadmium (Cd)-polluted Jinzu River basin and 40 reference subjects living in an adjacent area in 1994-95. They were 54 to 70 years old when the initial examination was conducted in 1983-84. In the Cd-polluted Jinzu River basin, extensive reclamation of polluted rice fields has been conducted since 1979; as a result, the average Cd concentrations in polished rice consumed by the subjects in the 1994-95 study (0.12ppm in 1994, 0.14ppm in 1995) were significantly lower than those in the 1983-84 study (0.26ppm in 1983, 0.29ppm in 1984). The average Cd levels in urine in the follow-up study (7.5μg/g Cr. in 1994, 7.7μg/g Cr. in 1995) were also significantly lower than those in the initial study (13.5μg/g Cr. in 1983, 13.3μg/g Cr. in 1984). However, the mean values for urinary excretion of β2-microglobulin (β2-m) (3.9mg/g Cr. in 1994, 3.7mg/g Cr. in 1995) and glucose (203mg/g Cr. in 1994, 251mg/g Cr. in 1995) in the follow-up study were significantly higher than those obtained at the initial examination (2.0mg/g Cr. and 125mg/g Cr. in 1983 and 1.1mg/g Cr. and 78mg/g Cr. in 1984 for β2-m and glucose excretion, respectively). The magnitude of increase in urinary excretion of β2-m and glucose in inhabitants of the Cd-polluted area was significantly higher than that of the inhabitants of the reference area. Moreover, an increase was observed in the prevalence of renal tubular dysfunction determined by urinary β2-m exceeding 10mg/g creatinine and urinary glucose exceeding 150mg/g creatinine only among inhabitants of the Cd-polluted area; it is noteworthy that 31 new cases of renal tubular dysfunction were observed in the follow-up study. These results indicate that renal tubular dysfunction among inbabitants of the Cd-polluted Jinzu River basin is irreversible and progressive, and many new cases of renal tubular dysfunction were also noted over a period of 11 years, despite the fact that Cd exposure had decreased over the past 11 years.