Is placenta a good indicator of cadmium and lead exposure?

Distribution of lead and cadmium was studied in 25 placentas. Samples were taken from 6 different lobuli, and lead and cadmium concentrations were not determined by graphite furnace atomic absorption spectrometry. Lead and cadmium were not distributed uniformly, and the concentrations differed by a factor > or = 2 among different lobuli within the same placenta in 36% and 52% of the placentas, respectively. Placental lead and cadmium concentrations were also determined in homogenized samples from smelter (n = 49) and control (n = 53) areas in northern Sweden. Mean lead and cadmium concentrations were low, even in the smelter area (geometric means = 10 ng/g and 3 ng/g wet weight, respectively). The significant differences observed (i.e., higher blood lead concentrations in the smelter area during pregnancy and in umbilical cord blood) were not reflected in the placenta. We concluded, therefore, that the placenta is not a suitable organ to use for the monitoring of environmental exposure to lead. It could be used to monitor cadmium exposure, but if pregnancy outcome is to be studied, consideration should be given to the sampling procedure.