Factor analysis of essential and toxic elements in human placentas from deliveries in artic and subarctic areas of Russia and Norway

Concentrations in human placenta of 11 essential elements (P, Ca, Mg, Cu, S , Na, Fe, Zn, K, Se, Mn) and 5 toxic elements (Ba, Sr, Pb, Ni, Cd) are comp ared for each of two arctic communities in eastern Norway and western Russi a, and for another in each country located at more southerly latitudes. All but Mg, Fe, P and K were present in higher concentrations in the Russian s tudy group. The observed inter-element correlations are reflected by the fo ur major factors identified in a principal component analysis. The total va riation explained was 67.3%, of which more than half (35.3%) was contribute d by Factor 1. P, Ca, Mg, Ba, Sr, Pb, and Ni were major contributors to thi s factor. The placental concentrations of these elements depended strongly on gestational age, increasing from about week 35 and peaking near weeks 39 and 40, and exhibited skewed frequency distributions and a dependence on m aternal smoking. The gestational-dependent mineralization of the placenta i s interpreted to reflect the deposition of metal phosphates coinciding with smoking-induced tissue damage. The loadings of the remaining three factors are reviewed in the context of common uptake mechanisms, similar biochemis tries and unique transport pathways. The inter-element relationships and gr ouping of the elements observed should constitute a scientific base for the use of placenta composition in environmental monitoring and epidemiologica l studies.