De Silva Amila O, Benskin Jonathan P, Martin Leah J, Arsenault Gilles, McCrindle Robert, Riddell Nicole, Martin Jonathan W, Mabury Scott A
Department of Chemistry, University of Toronto, Ontario, Canada.
Environ Toxicol Chem. 2009 Mar;28(3):555-67. doi: 10.1897/08-254.1. Epub 2008 Oct 21.
Two major industrial synthetic pathways have been used to produce perfluorinated acids (PFAs) or their precursors: Telomerization and electrochemical fluorination (ECF). Products of telomer and ECF origin can be distinguished by structural isomer profiles. A mixture of linear and branched perfluoroalkyl isomers is associated with ECF. Telomer products characteristically consist of a single perfluoroalkyl geometry, typically linear. In biota, it is unclear if the isomer profile is conserved relative to the exposure medium and hence whether PFA isomer profiles in organisms are useful for distinguishing environmental PFA sources. A companion study suggested isomer-specific disposition following a single oral gavage exposure to rats. To confirm these findings under a more realistic subchronic feeding scenario, male and female rats were administered PFA isomers by diet for 12 weeks, followed by a 12-week depuration period. The diet contained 500 ng/g each of ECF perfluorooctanoate (PFOA, approximately 80% n-PFOA), ECF perfluorooctane sulfonate (PFOS, approximately 70% n-PFOS), and linear and isopropyl perfluorononanoate (n- and iso-PFNA). Blood sampling during the exposure phase revealed preferential accumulation of n-PFOA and n-PFNA compared to most branched isomers. Female rats depurated all isomers faster than males. Both sexes eliminated most branched perfluorocarboxylate isomers more rapidly than the n-isomer. Elimination rates of the major branched PFOS isomers were not statistically different from n-PFOS. Two minor isomers of ECF PFOA and one branched PFOS isomer had longer elimination half-lives than the n-isomers. Although extrapolation of these pharmacokinetics trends in rats to humans and wildlife requires careful consideration of dosage level and species-specific physiology, cumulative evidence suggests that perfluorocarboxylate isomer profiles in biota may not be suitable for quantifying the relative contributions of telomer and ECF sources.
两种主要的工业合成途径已被用于生产全氟辛酸（PFAs）或其前体：调聚反应和电化学氟化（ECF）。调聚反应和ECF来源的产物可以通过结构异构体谱来区分。线性和支链全氟烷基异构体的混合物与ECF有关。调聚产物的特征是由单一的全氟烷基几何结构组成，通常是线性的。在生物群中，尚不清楚异构体谱相对于暴露介质是否保守，因此生物体中的PFA异构体谱是否有助于区分环境PFA来源也不明确。一项配套研究表明，大鼠单次经口灌胃暴露后存在异构体特异性处置情况。为了在更现实的亚慢性喂养情况下证实这些发现，对雄性和雌性大鼠通过饮食给予PFA异构体12周，随后进行12周的净化期。饮食中每种含有500 ng/g的ECF全氟辛酸（PFOA，约80%为正PFOA）、ECF全氟辛烷磺酸（PFOS，约70%为正PFOS）以及线性和异丙基全氟壬酸（正和异PFNA）。暴露阶段的血液采样显示，与大多数支链异构体相比，正PFOA和正PFNA优先积累。雌性大鼠比雄性大鼠更快地清除所有异构体。两性清除大多数支链全氟羧酸盐异构体的速度都比正异构体快。主要支链PFOS异构体的清除率与正PFOS在统计学上没有差异。ECF PFOA的两种次要异构体和一种支链PFOS异构体的消除半衰期比正异构体更长。尽管将大鼠的这些药代动力学趋势外推至人类和野生动物需要仔细考虑剂量水平和物种特异性生理学，但累积证据表明，生物群中的全氟羧酸盐异构体谱可能不适用于量化调聚反应和ECF来源的相对贡献。
