The principal factor determining how much cadmium is absorbed is the route of exposure. Once exposed, how much
cadmium is absorbed depends on many factors:
- smoking, and
- nutritional status.
As a cumulative toxin, cadmium body burden increases with age. Women have been shown to have higher blood levels of cadmium than men. Typically
women, with lower iron status, are believed to be at risk for greater absorption of cadmium after oral exposure (Olsson et al. 2002).
Once in the lungs, from 10% to 50% of an inhaled dose is absorbed, depending on particle size, solubility of the specific cadmium compound inhaled,
and duration of exposure (Jarup 2002). Absorption is least for large (greater than 10 micrometers [µm]) and water-insoluble particles,
and greatest for particles that are small (less than 0.1 µm) and water soluble. A high proportion of cadmium in cigarette smoke is absorbed because the cadmium particles found in that type of smoke are very small (ATSDR 1999).
Most orally ingested cadmium passes through the gastrointestinal tract unchanged as normal individuals absorb only about 6% of ingested cadmium,
but up to 9% may be absorbed in those with iron deficiency (ATSDR 1999). Also, cadmium in water is more easily absorbed than cadmium in food
(5% in water versus 2.5% in food) (IRIS 2006). The presence of elevated zinc or chromium in the diet decreases cadmium uptake.
Absorption through the skin is not a significant route of cadmium entry; only about 0.5% of cadmium is absorbed by the skin (ATSDR 1999).