Prenatal exposure to persistent organic pollutants in Northern Tanzania and their distribution between breast milk, maternal blood, placenta and cord blood

Human exposure to persistent organic pollutants (POPs) begins during pregnancy and may cause adverse health effects in the fetus or later in life. The present study aimed to assess prenatal POPs exposure to Tanzanian infants and evaluate the distribution of POPs between breast milk, maternal blood, placenta and cord blood. For assessment of prenatal exposure, 48 maternal blood samples from Mount Meru Regional Referral Hospital (MMRRH), Arusha Tanzania, were analyzed for organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), brominated flame retardants (BFRs), dioxin-like (DL) activity and perfluorinated alkyl substances (PFASs). For evaluation of POPs distribution between maternal/infant compartments, breast milk, placenta and cord blood corresponding to the maternal blood were analyzed for OCPs, PCBs and BFRs. In maternal blood, p,p´- DDE was detected in 100% of the samples ranging between 29 and 1890 ng/g lipid weight (lw). PCB-153 was the only PCB detected in maternal blood, with detection rate of 29% and concentrations up to 116 ng/g lw. BDE-47 was detected in 65% of the maternal blood samples, ranging between <LOD and 83.2 ng/g lw. DL activity was measured using Dioxin Responsive CALUX® bioassay. The DL activity was above LOQ in 92% of the samples, ranging from <LOQ to 114 pg CALUX TEQ/g lw. PFASs was dominated by PFOS and PFOA, however, the concentrations were low (range ∑PFASs 0.18-3.14 ng/mL). p,p´-DDE was detected in 100% of the breast milk, placenta and cord blood samples and the concentrations were strongly correlated (r = 0.89-0.98) between all compartments. Maternal blood (MB) had significantly lower p,p´-DDE concentrations (ng/g lw) than cord blood (CB) and breast milk (BM). The median CB/MB ratio was 1.3 and median MB/BM ratio was 0.8. p,p´-DDE concentrations in breast milk and cord blood did not show significant difference and median CB/BM ratio was 1. In addition, the relative p,p`-DDE transfer from maternal blood to breast milk and to cord blood increased when p,p`-DDE concentrations in maternal blood increased. This study shows that Tanzanian infants are exposed to a wide range of POPs during fetal life, which raise concerns for potential health effects. In addition, this study found that maternal blood concentrations may lead to underestimation of prenatal exposure, while breast milk collected close to delivery may be a more suitable indicator of prenatal exposure.

Simple physicochemical properties related with lipophilicity, polarity, molecular size and ionization status exert significant impact on the transfer of drugs and chemicals into human breast milk

OBJECTIVES

The transfer of xenobiotic compounds into human breast milk has raised serious concerns in the last few years. The present study is aimed to assess whether simple physicochemical properties exert significant impact on human breast milk transfer of drugs and chemicals.

METHODS

A large data set of 375 xenobiotic compounds with available experimental milk to plasma (M/P) ratios was systematically compiled from the literature and explored with their physicochemical properties being further analyzed with respect to their extent to transfer into breast milk.

RESULTS

Xenobiotic compounds with increased breast milk transfer (M/P ≥ 1) were characterized by enhanced lipophilicity and decreased molecular size (p < 0.05). Enhanced polarity and hydrogen bonding capacity were more frequently observed in xenobiotic compounds with reduced breast milk transfer (p < 0.0001). Xenobiotic compounds presenting increased positive charge at pH 7.4 were characterized by enhanced breast milk transfer (p < 0.001). Xenobiotic compounds presenting increased negative charge at pH 7.4 were characterized by decreased breast milk transfer (p < 0.001).

CONCLUSIONS

The present study supports evidence that simple physicochemical properties related with lipophilicity, polarity, molecular size and ionization status exert significant impact on drugs and chemicals transport into human breast milk.