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

Part 1. Changes in the level of exposure to cadmium after soil replacement of polluted paddy fields and the related effects on the prognosis of renal tubular dysfunction

Abstract

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.