John Wiley & Sons, Ltd.

A reductionist mechanistic model for bioconcentration of neutral and weakly polar organic compounds in fish

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The bioconcentration factor (BCF) of neutral and weakly polar organic chemicals in fish is modeled using independently calibrated models of chemical partitioning (φsys, KFW), respiratory exchange (k1, k2 = k1/KFW), and biotransformation (kM) as BCF = φsysKFW/(1 + kM/k2). Existing k1 models tend to overestimate for chemicals with logKOW < 3.5, which constituted 30–50% of the examined chemicals. A revised k1 model covering a wider logKOW range (0–8.5) is presented k1 = (5.46 × 10−6MW + 0.261/KOW)−1, where MW is the molecular weight. The biotransformation rate constant kM is modeled using biota internal partitioning and Abraham parameters as reactivity descriptors. The reductionist model was tested using 3 different BCF data sets (EPI, n = 548; Hertfordshire, n = 210; Arnot‐Gobas, n = 1855) and compared to 3 state‐of‐the‐art models: (i) the EPI Suite BCFBAF module, (ii) CAESAR, and (iii) the EPI/Arnot mechanistic kinetic model. The reductionist model performed comparably with the alternative models (RMSEs = 0.72–0.77) with only 5 fitting parameters and no training against experimental BCFs. Respiratory elimination and biotransformation dominate the total depuration (i.e., (k2 + kM)/kT ≥ 0.8) for approximately 98% of the data entries, thus validating the reductionist approximation. Mechanistic models exhibit greater insights and sensitivity to biological variation. The present study shows that a streamlined mechanistic model of BCF is possible for assessment purposes. Environ Toxicol Chem © 2013 SETAC

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