Development and evaluation of a mechanistic bioconcentration model for ionogenic organic chemicals in fish. (21st November 2012)

• Record Type: Journal Article
• Authors: Armitage, James M.; Arnot, Jon A.; Wania, Frank; Mackay, Don
• Is Part Of: Environmental toxicology and chemistry. Volume 32:Number 1(2013:Jan.)
• Page Start: 115
• Page End: 128
• Publication Date: 2012-11-21
• Subjects: Pollution -- Environmental aspects -- Periodicals; Environmental chemistry -- Periodicals; 615.902
• DOI: 10.1002/etc.2020
• Languages: English
• ISSNs: 0730-7268

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>A mechanistic mass balance bioconcentration model is developed and parameterized for ionogenic organic chemicals (IOCs) in fish and evaluated against a compilation of empirical bioconcentration factors (BCFs). The model is subsequently applied to a set of perfluoroalkyl acids. Key aspects of model development include revised methods to estimate the chemical absorption efficiency of IOCs at the respiratory surface (<italic>E</italic><sub>W</sub>) and the use of distribution ratios to characterize the overall sorption capacity of the organism. Membrane–water distribution ratios (<italic>D</italic><sub>MW</sub>) are used to characterize sorption to phospholipids instead of only considering the octanol–water distribution ratio (<italic>D</italic><sub>OW</sub>). Modeled BCFs are well correlated with the observations (e.g., <italic>r</italic><sup>2</sup> = 0.68 and 0.75 for organic acids and bases, respectively) and accurate to within a factor of three on average. Model prediction errors appear to be largely the result of uncertainties in the biotransformation rate constant (<italic>k</italic><sub>M</sub>) estimates and the generic approaches for estimating sorption capacity (e.g., <italic>D</italic><sub>MW</sub>). Model performance for the set of perfluoroalkyl acids considered is highly dependent on the input parameters describing hydrophobicity (i.e., log <italic>K</italic><sub>OW</sub> of the neutral form). The model applications broadly support the hypothesis that phospholipids contribute substantially to the sorption capacity of fish, particularly for compounds that exhibit a high degree of ionization at biologically relevant pH. Additional empirical data on biotransformation and sorption to phospholipids and subsequent incorporation into property estimation approaches (e.g., <italic>k</italic><sub>M</sub>, <italic>D</italic><sub>MW</sub>) are priorities with respect to improving model performance. Environ. Toxicol. Chem. 2013;32:115–128. © 2012 SETAC</p> </abstract>