School of Environmental and Chemical Engineering, Shanghai University, Shanghai 200444, PR China.
School of Environmental and Chemical Engineering, Shanghai University, Shanghai 200444, PR China; Guangdong Key Laboratory of Environmental Catalysis and Health Risk Control, Guangzhou Key Laboratory of Environmental Catalysis and Pollution Control, School of Environmental Science and Engineering, Institute of Environmental Health and Pollution Control, Guangdong University of Technology, Guangzhou 510006, PR China.
Environ Int. 2021 Jan;146:106224. doi: 10.1016/j.envint.2020.106224. Epub 2020 Nov 1.
Persistent halogenated organic pollutants (HOPs) are a class of toxic chemicals, which may have adverse effects on fetuses via transplacental transfer from their mothers. Here, we review reported internal exposure levels of various HOPs (organochlorinated pesticides, polychlorinated biphenyls, polybrominated diphenyl ethers, short- and medium-chain chlorinated paraffins, and per- and poly-fluoroalkyl substances) in placenta, and both maternal and umbilical cord sera. We also present analyses of the transplacental transfer and placental distribution characteristics of each class of compounds, and discuss effects of several factors on the transfer and accumulation efficiencies of HOPs, as well as the main mechanisms of HOPs' transfer across the placental barrier. Reported compound-specific transplacental transfer efficiencies and distribution efficiencies, expressed as umbilical cord:maternal serum and placental:maternal serum concentration ratios (R and R, respectively), are summarized. Average published R values of the HOPs range from 0.24 to 3.08 (lipid-adjusted) and from 0.04 to 3.1 (based on wet weights), and are highest for perfluoroalkylcarboxylates (PFCAs) and tetrabromobisphenol A. Average published R values range from 0.14 to 1.02 (lipid-adjusted) and from 0.30 to 1.4 (based on wet weights). The broad R and R ranges may reflect effects of various factors, inter alia physicochemical properties of HOPs, metabolic capacities of mothers and fetuses, placental maturity, and differential expression of influx/efflux transporters in the placenta. Generally, HOPs' R values decline linearly with molecular size, and are curvilinearly related to solubility. Plasma protein binding affinity and the difference between maternal and fetal metabolic capacities may also affect some HOPs' transfer efficiencies. HOPs' molecular size may be influential. Transplacental transport of HOPs likely occurs mostly through passive diffusion, although influx/efflux transporters expressed on maternal and/or fetal sides of the placenta may also facilitate or hinder their transport. Overall, the review highlights clear gaps in our understanding of mechanisms involved in HOPs' transplacental transport.
持久性卤代有机污染物（HOPs）是一类有毒化学物质，它们可能通过母体向胎儿的胎盘转移而对胎儿产生不良影响。在这里，我们回顾了各种 HOPs（有机氯农药、多氯联苯、多溴二苯醚、短链和中链氯化石蜡以及全氟和多氟烷基物质）在胎盘以及母体和脐带血清中的内部暴露水平。我们还介绍了每种化合物的胎盘转移和胎盘分布特征的分析，并讨论了几个因素对 HOPs 转移和积累效率的影响，以及 HOPs 通过胎盘屏障转移的主要机制。总结了报告的化合物特异性胎盘转移效率和分布效率，分别表示为脐带：母体血清和胎盘：母体血清浓度比（R 和 R）。HOP 的平均公布 R 值范围为 0.24 至 3.08（脂质调整）和 0.04 至 3.1（基于湿重），最高的是全氟烷基羧酸（PFCAs）和四溴双酚 A。HOP 的平均公布 R 值范围为 0.14 至 1.02（脂质调整）和 0.30 至 1.4（基于湿重）。广泛的 R 和 R 范围可能反映了各种因素的影响，除其他外，HOPs 的物理化学性质、母亲和胎儿的代谢能力、胎盘成熟度以及胎盘内外流/流入转运体的差异表达。通常，HOPs 的 R 值随分子大小线性下降，与溶解度呈曲线关系。血浆蛋白结合亲和力以及母体和胎儿代谢能力的差异也可能影响一些 HOPs 的转移效率。HOPs 的分子大小可能具有影响力。HOPs 的胎盘转移可能主要通过被动扩散发生，尽管胎盘母体和/或胎儿侧表达的流入/流出转运体也可能促进或阻碍其转运。总的来说，该综述突出了我们对 HOPs 胎盘转移机制理解中的明显差距。
