Prenatal exposure levels of polybrominated diphenyl ethers in mother-infant pairs and their transplacental transfer characteristics in Uganda (East Africa)

Polybrominated diphenyl ethers (PBDEs) are ubiquitous environmental pollutants with adverse effects on the foetus and infants. This study aimed at assessing in utero exposure levels and transplacental transfer (TPT) characteristics of BDE congeners in primiparous mothers from Kampala, the capital city of Uganda. Paired human samples (30 placenta and 30 cord blood samples) were collected between April and June 2018; and analysed for a suite of 24 tri-to deca-BDE congeners. Extraction was carried out using liquid-liquid extraction and sonication for cord blood and placenta samples, respectively. Clean-up was done on a solid phase (SPE) column and analysis was performed using gas chromatography/mass spectrometry (GC/MS). Total (∑) PBDEs were 0.25–30.9 ng/g lipid weight (lw) (median; 7.11 ng/g lw) in placental tissues and 1.65–34.5 ng/g lw (median; 11.9 ng/g lw) in cord blood serum, with a mean difference of 1.26 ng/g lw between the compartments. Statistical analysis showed no significant difference between the levels of PBDEs in cord blood and placenta samples (Wilcoxon signed rank test, p = 0.665), possibly because foetus and neonates have poorly developed systems to metabolise the pollutants from the mothers. BDE-209 was the dominant congener in both matrices (contributed 40.5% and 51.2% to ∑PBDEs in placenta and cord blood, respectively), suggesting recent and on-going maternal exposure to deca-BDE formulation. Non-significant associations were observed between ∑PBDEs in maternal placenta and maternal age, household income, pre-pregnancy body mass index (BMI), and beef/fish consumption. This suggested on-going exposure to PBDEs through multiple sources such as dust from indoor/outdoor environments and, ingestion of other foods. Based on absolute concentrations, the extent of transplacental transport was greater for higher congeners (BDE-209, -206 and −207) than for lower ones (such as BDE-47), suggesting alternative TPT mechanisms besides passive diffusion. More studies with bigger sample sizes are required to confirm these findings.