Abstract
In 1981, the soil of cadmium (Cd)-polluted rice fields was replaced with new soil in Kashine, a Cd-polluted district located on Tsushima Island, Nagasaki Prefecture, Japan. Consequently, the average dietary Cd intake among the inhabitants decreased from 215μg/day in 1969 to 106μg/day in 1983. The authors investigated the health status of Kashine inhabitants before and after the reduction of Cd intake. Concentrations of β2-microglobulin in urine (U-β2-mg) and Cd in urine (U-Cd), hair (H-Cd) and blood (B-Cd) were measured on 35 inhabitants in 1979 and 1996.
The geometric mean of U-β2-mg concentration for 9 subjects with U-β2-mg levels≥1, 000μg/g creatinine (μg/g cr) in 1979 increased by approximately 2.5-fold in 1996. Meanwhile there was littl echange in the geometric mean for 26 subjects with U-β2-mg levels<1, 000μg/g cr in 1996. It was concluded that renal tubular dysfunction among Cd-exposed inhabitants was irreversible and progressive, even after dietary Cd intake decreased.
The geometric mean of U-Cd concentration decreased significantly from 11.0μg/g cr in 1979 to 6.3μg/g cr in 1996. The decrease in U-Cd concentrations was significantly greater among inhabitants with U-β2-mg levels≥1, 000μg/g cr than among those with U-β2-mg levels<1, 000μg/g cr (p=0.03). From these results, it was considered that the level of U-Cd was more decreased by the presence of renal tubular dysfunction.
The geometric mean of H-Cd concentration decreased significantly from 109.1μg/kg in 1979 to 55.1μg/kg in 1996. However, it was unclear whether the decrease of H-Cd depended on the decrease of dietary Cd intake, decrease of body burden or both, because U-Cd concentrations also decreased by approximately 43% during this period. H-Cd concentration was weakly and positively correlated with U-Cd (r=0.38∼0.44), an indicator of body burden of Cd. These results suggested that H-Cd concentration was influenced by the body burden of this metal.
The geometric mean of B-Cd concentration in 33 inhabitants was 5.7μg/l in 1996. The geometric mean was signifcantly greater in subjects with initial U-β2-mg levels≥1, 000μg/g cr than in those with U-β2-mg levels<1, 000μg/g cr. A close positive correlation was found between B-Cd concentrations and U-Cd (r=0.70, p<0.01). It was suggested that the body burden influenced the levels of B-Cd as well as U-Cd, many years after Cd exposure had decreased.
