The relationship between placental cadmium, zinc, and copper

A number of interactions between the essential metals zinc (Zn) and copper (Cu), and the toxic metal cadmium (Cd), have been described in animal, but not in human tissues. The purpose of this study was to determine whether Cd levels are directly related to Zn or Cu levels in the human placenta at term, and whether this relationship is affected by parity or smoking. Atomic absorption spectroscopy was used to determine Cd, Zn and Cu in perfused placental cotyledons from 292 low-risk parturients. Plasma thiocyanate levels were used to determine smoking status. Linear regression and repeated measures analysis of variance (ANOVA) were used to examine relationships between the elements and the effects of parity and smoking status. Results show significant correlations between placental Cd and both Zn (r-0.41; p < 0.01) and Cu (r-0.35; p < 0.01), but only in multiparous patients. These relationships were not altered by smoking. These results suggest that Cd-Zn and Cd-Cu interactions occur in the placenta at "normal" levels of Cd exposure and over a very short time period.