Maternal–Fetal Transfer and Toxicokinetics of 2,2′,5,5′-Tetrachlorobiphenyl, [¹⁴C]-PCB52, Following Intratracheal Administration

Despite increased recognition of the adverse impacts of PCB exposure on human health, comprehensive risk assessments, particularly regarding inhalation exposure and effects on the developing fetus, are lacking. Out of all PCB congeners, lower-chlorinated PCBs have been more prevalent in indoor and outdoor atmospheres. Thus, we investigated in vivo toxicokinetics and placental transfer of radiolabeled [¹⁴C]-PCB52 (0.157 mg/kg administered intratracheally) in Sprague–Dawley rats at gestational day 11 ± 1. Following dosing, 99.4 ± 0.5% of the administered dose was distributed to the systemic circulation. Radioactivity disappeared biexponentially following lung exposure, with 41.1% of the dose retained after 96 h. PCB52 was rapidly distributed to the maternal serum, lung, heart, and liver, with subsequent accumulation in the ovaries, brain, white and brown adipose, muscle, and mammary glands. The time to reach a maximum concentration in the maternal serum was 0.21 h, with an apparent terminal elimination half-life of 40.7 h. The peak concentration of [¹⁴C]-PCB52 and its metabolites in the placenta, fetus, and amniotic fluid was achieved 1.7 h after exposure, with a fetal half-life of 34.8 h. The maternal serum level was significantly correlated with levels in amniotic fluid, placenta, fetus, and the maternal brain. However, PCB52 exposure in the placenta, fetus, and amniotic fluid was limited with their respective maternal serum exposure ratio values of 0.5, 0.27, and 0.05. These results demonstrate for the first time a comprehensive whole-body disposition of PCB52 in dams and fetuses after lung exposure during gestation. PCB52 and its metabolites accumulate predominantly in the ovaries, brain, and mammary glands. The apparent half-life of PCB52 in developing fetuses and placenta is comparable to that of maternal serum. This study provides novel quantitative foundations for the development and evaluation of physiologically based toxicokinetic modeling to inform the exposure and risk assessment for public health decisions.