Elimination
Most cadmium that is ingested or inhaled and transported to the gut via mucociliary clearance is excreted in the feces. Almost all fecal cadmium represents material that was not absorbed from the gastrointestinal tract. Most absorbed cadmium is excreted very slowly, with urinary and fecal excretion being approximately equal. Cadmium is also eliminated through hair and breast milk, but these routes are of limited importance for total excretion and do not significantly alter the biological half-time.
The placenta is only a partial barrier to fetal exposure to cadmium.
Several studies have shown that in the general population urinary cadmium excretion increases with age, this increase coinciding with the increased body burden. Smokers have higher urinary excretion than non-smokers. The amount of cadmium excreted represents only a small fraction of the total body burden unless renal damage is present.
Following oral exposure, the major proportion of administered cadmium is found in the feces, because absorption is low.