Bioconcentration of hydrophobic chemicals in fish: Relationship with membrane permeation

Abstract

Abstract A model is presented for the bioconcentration in fish of nonpolar hydrophobic chemicals that are not metabolized. The model assumes that diffusion rates through membrane-diffusion layer barriers influence uptake and depuration kinetics in fish. For extremely hydrophobic (log Kd, oct > 3 to 4) chemicals, uptake rate constants in fish are independent of the solute's hydrophobicity, whereas for low to moderately hydrophobic chemicals proportionality between these parameters is observed. Additionally, elimination rate constants for low to moderately hydrophobic chemicals are independent of the solute's hydrophobicity. In contrast, the elimination rate constants for extremely hydrophobic chemicals, such as polychlorobenzenes and -naphthalenes, are inversely proportional to hydrophobicity. In the model presented, this is due to the rates of release from the lipid compartments of the fish. The general relationships between bioconcentration kinetic parameters and hydrophobicity are in agreement with experimental data.