| 1. |
- Droge, Steven T. J., et al.
(författare)
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Screening the baseline fish bioconcentration factor of various types of surfactants using phospholipid binding data
- 2021
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Ingår i: Environmental Science. - : Royal Society of Chemistry (RSC). - 2050-7887 .- 2050-7895. ; 23:12
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Tidskriftsartikel (refereegranskat)abstract
- Fish bioconcentration factors (BCFs) are commonly used in chemical hazard and risk assessment. For neutral organic chemicals BCFs are positively correlated with the octanol-water partition ratio (K-OW), but K-OW is not a reliable parameter for surfactants. Membrane lipid-water distribution ratios (D-MLW) can be accurately measured for all kinds of surfactants, using phospholipid-based sorbents. This study first demonstrates that D-MLW values for ionic surfactants are more than 100 000 times higher than the partition ratio to fish-oil, representing neutral storage lipid. A non-ionic alcohol ethoxylate surfactant showed almost equal affinity for both lipid types. Accordingly, a baseline screening BCF value for surfactants (BCFbaseline) can be approximated for ionic surfactants by multiplying D-MLW by the phospholipid fraction in tissue, and for non-ionic surfactants by multiplying D-MLW by the total lipid fraction. We measured D-MLW values for surfactant structures, including linear and branched alkylbenzenesulfonates, an alkylsulfoacetate and an alkylethersulfate, bis(2-ethylhexyl)-surfactants (e.g., docusate), zwitterionic alkylbetaines and alkylamine-oxides, and a polyprotic diamine. Together with sixty previously published D-MLW values for surfactants, structure-activity relationships were derived to elucidate the influence of surfactant specific molecular features on D-MLW. For 23 surfactant types, we established the alkyl chain length at which BCFbaseline would exceed the EU REACH bioaccumulation (B) threshold of 2000 L kg(-1), and would therefore require higher tier assessments to further refine the BCF estimate. Finally, the derived BCFbaseline are compared with measured literature in vivo BCF data where available, suggesting that refinements, most notably reliable estimates of biotransformation rates, are needed for most surfactant types.
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| 2. |
- Kierkegaard, Amelie, et al.
(författare)
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Bioconcentration of Several Series of Cationic Surfactants in Rainbow Trout
- 2021
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 55:13, s. 8888-8897
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Tidskriftsartikel (refereegranskat)abstract
- Cationic surfactants have a strong affinity to sorb to phospholipid membranes and thus possess an inherent potential to bioaccumulate, but there are few measurements of bioconcentration in fish. We measured the bioconcentration of 10 alkylamines plus two quaternary ammonium compounds in juvenile rainbow trout at pH 7.6, and repeated the measurements at pH 6.2 for 6 of these surfactants. The BCF of the amines with chain lengths <= C-14 was positively correlated with chain length, increasing similar to 0.5 log units per carbon. Their BCF was also pH dependent and approximately proportional to the neutral fraction of the amine in the water. The BCFs of the quaternary ammonium compounds showed no pH dependence and were >2 orders of magnitude less than for amines of the same chain length at pH 7.6. This indicates that systemic uptake of permanently charged cationic surfactants is limited. The behavior of the quaternary ammonium compounds and the two C-16 amines studied was consistent with previous observations that these surfactants accumulate primarily to the gills and external surfaces of the fish. At pH 7.6 the BCF exceeded 2000 L kg(-1) for 4 amines with chains >= C-13, showing that bioconcentration can be considerable for some longer chained cationic surfactants.
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| 3. |
- McLachlan, Michael S., et al.
(författare)
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A framework for understanding the bioconcentration of surfactants in fish
- 2023
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Ingår i: Environmental Science. - 2050-7887 .- 2050-7895. ; 25:7, s. 1238-1251
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Tidskriftsartikel (refereegranskat)abstract
- Surfactants are a class of chemicals released in large quantities to water, and therefore bioconcentration in fish is an important component of their safety assessment. Their structural diversity, which encompasses nonionic, anionic, cationic and zwitterionic molecules with a broad range of lipophilicity, makes their evaluation challenging. A strong influence of environmental pH adds a further layer of complexity to their bioconcentration assessment. Here we present a framework that penetrates this complexity. Using simple equations derived from current understanding of the relevant underlying processes, we plot the key bioconcentration parameters (uptake rate constant, elimination rate constant and bioconcentration factor) as a function of its membrane lipid/water distribution ratio and the neutral fraction of the chemical in water at pH 8.1 and at pH 6.1. On this chemical space plot, we indicate boundaries at which four resistance terms (perfusion with water, transcellular, paracellular, and perfusion with blood) limit transport of surfactants across the gills. We then show that the bioconcentration parameters predicted by this framework align well with in vivo measurements of anionic, cationic and nonionic surfactants in fish. In doing so, we demonstrate how the framework can be used to explore expected differences in bioconcentration behavior within a given sub-class of surfactants, to assess how pH will influence bioconcentration, to identify the underlying processes governing bioconcentration of a particular surfactant, and to discover knowledge gaps that require further research. This framework for amphiphilic chemicals may function as a template for improved understanding of the accumulation potential of other ionizable chemicals of environmental concern, such as pharmaceuticals or dyes.
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| 4. |
- Ribbenstedt, Anton, 1986-, et al.
(författare)
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In Vivo Bioconcentration of 10 Anionic Surfactants in Rainbow Trout Explained by In Vitro Data on Partitioning and S9 Clearance
- 2022
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 56:10, s. 6305-6314
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Tidskriftsartikel (refereegranskat)abstract
- Bioconcentration factors (BCFs) in rainbow trout were measured for 10 anionic surfactants with a range of alkyl chain lengths and different polar head groups. The BCFs ranged from 0.04 L kg–1 ww (for C10SO3) to 1370 L kg–1 ww (C16SO3). There was a strong correlation between the log BCF and log membrane lipid–water distribution ratio (DMLW, r2 = 0.96), and biotransformation was identified as the dominant elimination mechanism. The strong positive influence of DMLW on BCF was attributed to two phenomena: (i) increased partitioning from water into the epithelial membrane of the gill, leading to more rapid diffusion across this barrier and more rapid uptake, and (ii) increased sequestration of the surfactant body burden into membranes and other body tissues, resulting in lower freely dissolved concentrations available for biotransformation. Estimated whole-body in vivo biotransformation rate constants kB-BCF are within a factor three of rate constants estimated from S9 in vitro assays for six of the eight test chemicals for which kB-BCF could be determined. A model-based assessment indicated that the hepatic clearance rate of freely dissolved chemicals was similar for the studied surfactants. The dataset will be useful for evaluation of in silico and in vitro methods to assess bioaccumulation.
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