Objectives: To estimate rates of cadmium (Cd) uptake from the digestive tract and changes in Cd in biological specimens after intake of Cd mainly in rice.
Methods: Twenty-five young non-smoking Japanese female volunteers (20-23 in age) were recruited and a 20-d experimental study was conducted. With polished rice containing 0.004 ppm and 0.340 ppm of Cd, Meal L and Meal H were prepared. Approximately 12% of total Cd in Meal L and 92% of total Cd in Meal H originated in rice. The volunteers ate Meal L for 11 d to achieve a stable intake-output balance of Cd. Fifteen of the 25 volunteers ate Meal H on the 12(th) day (Group D1), and the remaining 10 ate Meal H on the 12(th), 13(th) and 14(th) day (Group D3). All 25 subjects then resumed the consumption of Meal L to the end of the study (20(th) day). All meals, feces and urine were collected during the study, and Cd intake from the daily meals (Cd-I), Cd in feces (Cd-F) and Cd in urine (Cd-U) were determined. For measurement of Cd in blood (Cd-B), venous blood was collected from all volunteers on the day before the study and again on the 12(th) and 20(th) day; venous blood was also collected from 4-8 volunteers at additional time points.
Results: Mean Cd-I was 4.51 microg/d (range: 1.85-6.93) or 48.48 microg/d (range: 27.98-56.27) when they ate Meal L or Meal H. Cd-F and Cd-B exhibited faster responses to the change in Cd-I than did Cd-U. The Cd(uptake) rate, defined as (1-Cd-F(excess) /Cd-I(excess)) (Fig. 1), was 47.2% (range: -9.4-83.3%) in Group D1 and 36.6% (range: -9.2-73.5%) in Group D3, and the Cd(balance) rate, defined as (1-Cd-F(output) /Cd-I(intake)), was 23.9% (range: -4.0-37.7%) in Group D1 and 23.7% (range: -8.2-56.9%) in Group D3.
Conclusions: Cd-F and Cd-B are better biological monitoring parameters for assessing change in Cd-I than Cd-U. The Cd(uptake) and Cd(balance) rates appeared to be higher than those in previous papers when ingested Cd mainly originated in rice.