Biomonitoring of Cadmium - Relationship between Cadmium in Kidney, Blood and Urine, Interpretation of Urinary Cadmium, and Implications for Study Design

摘要

Cadmium is an environmental contaminant which accumulates in thekidney and can potentially affect human health at relatively lowconcentrations. Biomarkers such as cadmium in urine or blood arenormally used to assess the body burden of cadmium. We studied therelationship between cadmium in urine, blood, and kidney by using109 healthy environmentally exposed kidney donors. The variability inurinary cadmium excretion, its interpretation, and effects on the studydesign were further examined using repeated urinary samples from 30non-smoking healthy men and women. The results showed a strongassociation between cadmium in urine and kidney (rp=0.7), with anexcretion corresponding to a biological half-time of about 30 years. Akidney cadmium of 25 μg/g corresponded to a urinary cadmium of0.42 μg/g creatinine (i.e. a urine to kidney ratio of 1:60). Previousestimates of the urine to kidney cadmium ratio (1:20) may thusunderestimate the kidney cadmium at low urinary cadmium excretion.On average, 70% of the urinary cadmium excretion could be explainedby kidney cadmium. Urinary cadmium excretion was also affected bycadmium in blood and urinary albumin excretion. There was acircadian rhythm in the urinary cadmium excretion over 24h, affectingboth the interpretation of urinary cadmium measures and theappropriate study design. There was an association between urinarycadmium and urinary proteins within individuals. Hence, when urinarycadmium is used as a biomarker for cadmium body burden, normalshort-term variability in renal function may result in an overestimationof the nephrotoxicity of cadmium.