Urinary cadmium elimination as a biomarker of exposure for evaluating a cadmium dietary exposure-biokinetics model

The Cadmium Dietary Exposure Model (CDEM) utilizes national survey data on food cadmium concentrations and food consumption patterns to estimate dieta ry intakes in the U.S. population. The CDEM has been linked to a modificati on of the cadmium biokinetic model of Kjellstrom and Nordberg (KNM) to deri ve predictions of kidney and urinary cadmium that reflect U.S. dietary cadm ium intake and related variability. Variability in dietary cadmium intake w as propagated through the KNM using a Monte Carlo approach. The model predi cts a mean peak kidney cadmium burden of approximately 3.5 mg and a 5th-95t h percentile range of 2.2-5.1 mg in males. The corresponding peak renal cor tex cadmium concentration in males is 15 mug/g wet cortex (10-22, 5th-95th percentile). Predicted kidney cadmium levels in females were higher than ma les: 5.1 (3.3-7.6) mg total kidney, 29 (19-43) mug/g wet cortex. Predicted urinary cadmium in males and females agreed with empirical estimates based on the NHANES III, with females predicted and observed to excrete approxima tely twice the amount of cadmium in urine than males. An explanation for th e higher urinary cadmium excretion in females is proposed that is consisten t with the NHANES III data as well as experimental studies in humans and an imals. remakes may absorb a larger fraction of ingested dietary cadmium tha n males, and this difference may be the result of lower iron body stores in females compared to males. This would suggest that females may be at great er risk of developing cadmium toxicity than males. The predicted 5th-95th p ercentile values for peak kidney cadmium burden are approximately 60% of th e peak kidney burden (8-11 mg) predicted for a chronic intake at the U.S. E nvironmental Protection Agency (EPA) chronic reference dose of 1 mug/kg-d.