Adipose tissue deposition and placental transfer of persistent organic pollutants in ewes

Persistent organic pollutants (POPs) are known for their persistence, bioaccumulation, and potential to harm human health and wildlife. POPs cross the placenta, potentially predisposing the developing fetus to long-term health effects. Current biomonitoring of fetal exposure is mostly based on blood concentrations at birth. Research on the partition of POP burden between the maternal and fetal adipose tissues is scarce. This study analyzed common POPs (PeCB, HCB, α-HCH, β-HCH, γ-HCH, oxychlordane, p,p'-DDT, p,p'-DDE, and PCB-28, -52, -74, -99, -101, -118, -138, -153, -170, -180, -183, and -187; and PBDE-47, -99, -153) in perirenal adipose tissue of sheep ewe (n = 15) and respective lambs using GC-MS/MS. By near term all lambs had accumulated a mixture of POPs in their adipose tissue. The total burden of all measured POPs was slightly lower in the lambs compared to the ewes. Individual POP concentrations ranged from 3 to 2603 pg/g. Lamb-to-ewe concentration ratios varied from 0.30 for p,p'-DDT to 1.03 for β-HCH, indicating different compound-specific mechanisms for transplacental transfer and/or adipose tissue partitioning. β-HCH was the only POP that had a concentration ratio greater than 1. PCB-183 exhibited a higher lamb-to-ewe concentration ratio than other PCB congeners. In conclusion, while concentrations of POPs in ewes and lambs were low, their similar magnitude confirms significant transfer during pregnancy. Human fetuses may be exposed to higher concentrations due to higher POP levels in human adipose tissue, highlighting the need for more accurate fetal exposure assessment and research on the mechanisms of health effects of POPs.