DOSE-RESPONSE RELATIONSHIP BETWEEN TOTAL CADMIUM INTAKE AND PREVALENCE OF RENAL DYSFUNCTION USING GENERAL LINEAR-MODELS

To determine the maximum allowable intake limits for chronic dietary e xposure to cadmium (Cd), the dose-response relationship between total Cd intake and prevalence of renal dysfunction was examined using gener al linear models considering the effect of age as a confounder. The ta rget population comprised 1850 Cd-exposed and 294 non-exposed inhabita nts of Ishikawa, Japan. They were divided into 96 subgroups by sex, ag e (four categories) cadmium concentrations in rice (three categories) and length of residence (four categories). As indicators of the cadmiu m-induced renal dysfunction, glucose, total protein, amino nitrogen, b eta(2)-microglobulin and metallothionein in urine were employed. Gener al linear models were fitted statistically to the relationship among p revalence of renal dysfunction, sex, age and total Cd intake. Prevalen ce of abnormal urinary findings other than glucosuria had significant associations with total Cd intake. When total Cd intake corresponding to the mean prevalence of each abnormal urinary finding in the non-exp osed subjects was calculated using general linear models, total Cd int akes corresponding to glucosuria, proteinuria, aminoaciduria (men only ) and proteinuria with glucosuria were determined to be ca. 2.2-3.8 g and those corresponding to prevalence of metallothioneinuria were calc ulated as ca. 1.5-2.6 g. The low-molecular-weight protein in urine was confirmed to be a more sensitive indicator of renal dysfunction, and these total Cd intake values were close to those calculated previously by simple regression analysis, suggesting them to be reasonable value s as the maximum allowable intake of Cd.