Assessment of the causality of the cadmium--protein relationships in the urine of the general population with reference to the Cadmibel study.

The assessment of acceptable exposure levels to cadmium in the work or general environment frequently relies on the analysis of the relationships between urinary cadmium (an indicator of the body burden) and proteins used as markers of nephrotoxicity. A possibility which cannot be excluded a priori is that the relationships between cadmium and proteins in urine might sometimes result from renal dysfunction unrelated to cadmium toxicity. To test this hypothesis, we have measured cadmium in the urine of 114 pregnant women of whom about 20% had developed a reversible tubular proteinuria. Cadmium excretion was correlated significantly with age but not with duration of pregnancy nor with low molecular weight urinary proteins. This indicates that tubular dysfunction unrelated to cadmium exposure does not necessarily increase cadmium excretion. Hence, these data support the conclusion of the recent Cadmibel Study on the renal tubular effects of cadmium on the general population of Belgium.