Polychlorinated biphenyls and their hydroxylated metabolites in placenta from Madrid mothers

Concentrations and congener profiles of polychlorinated biphenyls (PCBs) and their hydroxylated metabolites (OH-PCBs) in placenta samples from a Madrid population (Spain) are reported. Structure dependent retentions of OH-PCBs are known to occur in both humans and wildlife, making it of interest to assess placental transfer of both parent compounds and their metabolites to the developing foetus.

The ΣPCB concentrations found in placenta samples were in the range 943-4,331 pg/g fresh weight (f.w.), and their hydroxylated metabolites showed a 20-time lower concentration level (53-261 pg/g f.w.). The PCB profiles were surprisingly dominated by CB-52 and CB-101 accounting for more than 44% of the total PCB concentration. This is indicating a source of exposure that is not yet identified. The OH-PCB profiles were dominated by 4-OH-CB187 and 4-OH-CB146, representing >50% of the ΣOH-PCB concentration of the placenta samples. Statistical analysis of the data revealed strong correlations between the PCB congeners, among some OH-PCBs, and between OH-PCB metabolites with a meta- and para- substitution pattern. Both PCB and OH-PCB concentrations presented homogeneous distribution, what allowed the establishment of a partial least squares model that correlated the concentrations of OH-PCB with those of PCBs in placenta samples. In addition, causal correlations were observed between the concentrations of OH-PCBs and those of their corresponding PCB precursors.