[The human placenta's lead level as a parameter of the ecological lead exposure. Its validity in comparison to the lead level in blood, the activity of the delta-aminolevulinic acid dehydratase and the concentration of the free erythrocyte porphyrins of newborns and their mothers (author's transl)].

In order to estimate the ecological exposure of lead, placenta- and blood-investigations were made at four collectives from variously industrialized regions (Ruhrregion, Middle Frankonia Centre, Bavarian Forest). 148 normal births and 19 premature births (in each case mothers and newborns) were listed as well as twelve abortions. We investigated the lead-level in blood, the activity of delta-aminolaevulinic acid dehydratase (ALA-D) the concentration of free erythrocyte porphyrine (FEP) and the placentas' lead concentration. Though in the Ruhrregion (Dortmund) significantly higher lead levels in blood were found compared to the Bavarian Forest, the results together, were in the normal range, less than 35 mug%. In an average the mothers' lead level in blood was around 1.4 times (ca. 5 mug%) above that of their newborns; analysing this statistically, highly significant correlations were found. However for the ALA-D activity and the FEP-results no direct dependence of the lead levels in blood could be found. In the placentas mean lead concentrations between 1.94 mug and 2.23 mug per gram dry-weight (30.6 mug-38.9 mug/100 g wet-weight) were gained. In the contrary to the measured results of lead in blood the average placentas' lead level of the most and least industrialized regions were almost identical. A correlation between the mothers' respectively their children's lead levels in blood and the placental lead concentrations could not be proved. No relation could be found between the results and the gestation ages. As final results: 1. The placenta is no ideal investigation object concerning the environment's lead exposure. 2. It has no special barriere - or depot - function in lead metabolism. 3. In order to estimate the environment's lead exposure the determination of the lead level in blood will also be in future the optimal method. This investigation is of special value because of its validity of the results and the practicability of winning the samples compared to other parameters and biological materials.