Estimated bioconcentration factors (BCFs) for the C₄through C₈perfluorinated alkylsulfonic acid (PFSA) and alkylcarboxylic acid (PFCA) congeners

Abstract

Bioconcentration factors (BCFs) were estimated for all congeners in each of the C(4) through C(8) homologue groups for perfluorinated alkylsulfonic acids (PFSAs) and alkylcarboxylic acids (PFCAs). Predictive equations were developed between molecular areas and volumes using optimized gas-phase geometries from the AM1 and PM3 semiempirical computational basis sets and previously determined BCFs for representative straight-chain members of each contaminant class. Molecular area approaches for estimating PFSA and PFCA BCFs resulted in more variability both between and within homologue groups than the use of molecular volumes as proxies for hydrophobicity of the perfluoroalkyl chain. An increasing degree of perfluoroalkyl chain branching within each homologue group reduces the estimated BCF, suggesting that the more linear PFSA and PFCA congeners will display the highest BCFs in aquatic organisms.

Using COSMOtherm to predict physicochemical properties of poly- and perfluorinated alkyl substances (PFASs)

“…[2,[51][52][53] However, they estimated properties for all theoretically possible isomers, whereas in reality only some of these occur. [32] In our estimations, the branched isomers of PFCAs exhibit a partitioning behaviour that may differ considerably from that of the linear counterparts, if all theoretically possible branched isomers are considered.…”

Congener specific organic carbon normalized soil and sediment-water partitioning coefficients for the C1 through C8 perfluoroalkyl carboxylic and sulfonic acids

“…[96][97][98] This proteinophilic behavior in vivo results in large bioconcentration factors (BCFs) and bioaccumulation factors (BAFs) in protein rich tissues such as the liver, blood, and kidneys for longer chain PFAs. [1,2,4,6,14,22,25,41,61,78,[99][100][101][102][103][104] The affinity for protein surfaces has also been recently exploited by the use of molecularly imprinted chitosan polymer adsorbents to remove PFAs from waste streams. [105] Perhaps because of the focus on their proteinophilic nature and the hydrophilic head group/oleophobic tail combination, a limited number of studies have investigated the partitioning of PFAs between more traditional organic materials and aqueous phases.…”

“…[99] The surfactant nature of PFAs has led a number of researchers and regulatory agencies to question the applicability of well established partitioning coefficients such as K ow and octanol-air (K oa ) constants, as well as the more general fugacity approach, in describing (either directly or as modified surrogate proxies) the behavior of PFAs in abiotic and biotic systems. [6,102,128] For example, it has been stated that soil and sediment adsorption coefficients (K d ) of PFAs "cannot be estimated with conventional quantitative structure relationship models (QSARs)."…”

“…Due to the increasing awareness of the large number of potential PFA congeners, [114] and the experimental costs in measuring a range of partitioning constants for each isomer, our recent efforts [85,99,[109][110][111]115] have been concentrated on using computational tools and available experimental datasets to predict the physicochemical properties of these compounds. In the present study, we synthesize the current state of the art regarding partitioning of PFAs between organic carbon and aqueous environments and present a congener specific model that estimates the organic carbon normalized soil and sediment-water partitioning (K oc ) coefficients for the C 1 through C 8 PFCA and PFSA isomers.…”

Toxicological Effects of Perfluoroalkyl and Polyfluoroalkyl Substances

“…Several controlled laboratory and fi eld bioaccumulation experiments with aquatic species indicate that PFHxA is not bioaccumulative (Martin et al 2003a , b ;Conder et al 2008 ;Rayne et al 2009 ;Yeung and Mabury 2013 ). Recent studies discussed toxicokinetics in mammals showing rapid elimination in rats, mice, monkeys and humans with elimination half-lives proportional to body weight with no difference between genders (Russell et al 2013 ).…”