The critical level of cadmium in renal cortex: the concept and its limitations.

Because renal cortex is a primary target organ of Cd the seriousness of human exposure is commonly assessed in terms of the extent to which it permits renal cortical Cd concentrations to approach a critical value. The critical value has been defined in terms of PCC-10, the population critical concentration at which 10% of exposed individuals may be expected to show abnormal renal function. In chronically exposed human populations, PCC-10 appears to lie in the range of 180 to 220 μg Cd/gram fresh weight of cortex. However, Cd accumulated in the kidney under these conditions is distributed between more than one compartment, in all likelihood differing greatly in their toxicological characteristics. For instance, a major fraction of this Cd is bound to metallothionein, and may as such be relatively inert. Compartmentation of tissue Cd, in turn, is strongly influenced by the nature of exposure, and the PCC-10 value of 200 μg/g may therefore have limited general significance. The problem of risk assessment is further complicated by the high variability of Cd absorption. Nevertheless, human renal Cd levels commonly reach values as high as 1/3 to 1/6 of the chronic PCC-10, and further increases in Cd intake should therefore be avoided.