Statistical observations of the dose-response relationships of cadmium based on epidemiological studies in the Kakehashi River basin.

Statistical analysis was performed on the results of the epidemiological study for Itai-itai disease carried out in 1974 and 1975 by Ishikawa Prefecture Health Authorities in the cadmium-polluted Kakehashi River basin.As indices of the effects of cadmium on health, we used the urinary excretion of retinol binding protein, of suspected patients, and of tubular dysfunction. As indices of cadmium exposure, village average cadmium concentration in rice and urine were employed. Close dose-response relationships between cadmium exposure and health effects were found to exist and the curves obtained indicated sigmoid lines when the inhabitants were stratified according to their village average rice or urinary cadmium concentrations. When retinol binding protein was employed as the index of the effect on health, significant differences, compared with the control, in inhabitants ages 60 to 69 were observed at the levels of 0.50–0.59 μg/g in rice or 9.0–10.9 μg/liter in urine as village averages and 0.60–0.69 μg/g in rice eaten by inhabitants ages 50 to 59. However, in the inhabitants more than 70 yr of age significant differences in the prevalence of tubular proteinuria were observed between the lowest polluted village and the control ones. This fact indicated that the prevalence of tubular proteinuria in these inhabitants increased continuously from the nonpolluted levels of cadmium.Probit analysis of urinary cadmium concentration and renal effects was performed on 262 inhabitants selected for close examination. Probit linear regression lines were obtained when the inhabitants were arranged according to their urinary cadmium concentrations expressed as micrograms per gram creatinine.