Sites of lead and nickel accumulation in the placental tissue.

1. There is a variety of quantitative analytical data regarding the total concentrations of heavy metals in human placentae. However, little is known about sites of metal accumulation in the placental tissue structural zones in relation to the environment. In this study, the lead and the nickel particulate deposits in the placental chorionic plate, the chorionic villous tree and the basal plate, using tissue histochemical reactions for lead and nickel, have been estimated. The degree of metal contamination of placentae was assessed according to an arbitrary scale. Both metals have shown a common mode of accumulation in the placental tissue structural zones. Among the observed contaminated structures in the placental tissue, the syncytiotrophoblast was the most frequent site for lead and nickel particulate deposits. 2. The frequency distribution of both metals within the mentioned placental zones, using four metal contamination degrees, was determined. A heavily contaminated zone was found to be the chorionic villous tree, especially in samples from the industrial region. 3. A comparison between two Slovak regions (an industrial and a rural one) using statistical tests was performed. The frequency of samples without any lead occurrence in the chorionic villous tree was found to be 10% in the industrial region, and 16% in the rural region. Regarding the nickel deposits, the frequency of non-contaminated samples in the industrial region was 2%, whereas in the rural region 6%. A relationship between traffic related pollution and human placenta contamination was found in both investigated regions.