Unique Physicochemical Properties of Perfluorinated Compounds and Their Bioconcentration in Common Carp Cyprinus carpio L.

Abstract

Carp (Cyprinus carpio L.) was exposed to perfluorinated compounds (PFCs)-perfluoroalkyl carboxylic acids (number of carbon atoms, C = 8, 11, 12, 14, 16, and 18) and perfluorooctane sulfonate (PFOS)-in bioconcentration tests to compare the bioconcentration factors (BCFs) and physicochemical properties of each specific compound. Despite having the same number of carbon atoms (C = 8), the BCFs of perfulorooctanoic acid (PFOA) and PFOS differed by more than two orders of magnitude (PFOA BCF = < 5.1 to 9.4; PFOS BCF = 720 to 1300). The highest BCFs were obtained from perfluorododecanoic acid (BCF = 10,000 to 16,000) and perfluorotetradecanoic acid (BCF = 16,000 to 17,000). The longest observed depuration half-lives were for perfluorohexadecanoic acid (48 to 54 days) and PFOS (45 to 52 days). The concentrations of PFCs were highest in the viscera, followed by the head, integument, and remaining parts of the test fish. PFCs concentrations in the integument, which was in direct contact with the test substances, were relatively greater than that of other lipophilic substance (hexachlorobenzene). It is likely that Clog P would be a better parameter than log K (ow) for the prediction of BCFs for PFCs. Threshold values for PFCs bioaccumulation potential (molecular weight = 700, maximum diameter = 2 nm) seemed to deviate from those generally reported because of the specific steric bulk effect of molecule size.

Development and evaluation of a mechanistic bioconcentration model for ionogenic organic chemicals in fish

“…Accordingly, whereas the neutral form can sorb to neutral (storage) lipids and phospholipids to a similar degree, the charged form is expected to sorb preferentially to phospholipids. This behavior is qualitatively consistent with the low wet-weight concentrations reported for PFAAs in adipose tissue of rainbow trout compared to liver and kidney [30,31]. Note that because D OW is expected to be larger than D MW for the majority of IOCs, mechanistic BCF modeling approaches using D OW only are expected to result in bias toward underestimation, particularly for chemicals exhibiting a high degree of ionization and affinity for phospholipids.…”

“…Additionally, the proposed model does not consider the possibility of concentration-dependent bioaccumulation potential, as reported in a semi-static exposure study with green mussels [61]. Note that this concentration-dependent bioaccumulation behavior was not consistently observed in experimental BCFs reported for carp exposed in flow-through experiments [31]. Values for key biological (e.g., W B , f SL and f PL ) and physicalchemical (e.g., D OW and D MW ) model input parameters are summarized in Supplemental Data, Section S8.…”

“…Whereas a great deal of attention has focused on elucidating the nature and strength of PFAA interactions with serum albumin and liver fatty acid proteins [24,25] (see Supplemental Data, Section S3), several studies have also demonstrated that PFAAs interact strongly with phospholipid bilayers [26][27][28][29]. The observation that elevated wet-weight concentrations of these compounds occur in organs expected to have relatively high phospholipid contents (e.g., liver $2% neutral lipid, 4.5% phospholipid, 15-20% protein vs muscle $0.4% neutral lipid, 0.4% phospholipid, 20% protein) [15,[30][31][32] is also highly suggestive. Though site-specific binding interactions (e.g., protein binding) exhibited by PFAAs may not be adequately characterized by the available approaches to describe sorption to biological macromolecules [33,34], it must also be recognized that other endogenous and exogenous ligands may have greater binding affinity and presence at binding sites, particularly when considering environmentally relevant exposure scenarios.…”

“…Seven compounds originally included in Fu et al [12] were not used for model evaluation in the present study due to low quality scores (i.e., PPDB reliability scores of 1, 2, or 3), leaving BCF data for 26 organic acids and 22 organic bases. The empirical BCF data for PFAAs reported by Martin et al [30] and Inoue et al [31] were also compiled (see Supplemental Data, Section S6) but kept separate from the model test set described above.…”

Progress toward understanding the bioaccumulation of perfluorinated alkyl acids

“…Recent bioconcentration measurements of PFCAs in carp (Cyprinus carpio) [13] have largely confirmed the BCFs reported by Martin et al [9] and demonstrated that long chain PFCAs are highly bioaccumulative. The assessment of aquatic bioaccumulation of PFASs using laboratory exposures has moved on to the precursor chemicals, including 8:2 fluorotelomer alcohol and FOSA [14], 8:2 fluorotelomer acrylate [15], and perfluorophosphonates and perfluorophosphinates [16].…”