Reduction in bioavailability to bluegills of polycyclic aromatic hydrocarbons bound to dissolved humic material

Abstract The uptake, depuration, metabolic fate and bioaccumulation of two polycyclic aromatic hydrocarbons (PAH), [14C]naphthalene (NPH) and [14C]benzo(α)pyrene (BaP), by bluegill sunfish were determined in the presence and absence of dissolved humic material (DHM) (20 mg C/L) The effect of binding to DHM on the bioavailability of PAH was analyzed by multicompartment kinetic models to determine the relative rates of uptake of PAH dissolved in water versus that bound to DHM. DHM reduced the accumulation of BaP by 90% (97% of BaP bound to DHM) but had little effect on uptake of NPH (2% bound to DHM). The rate coefficients for uptake of bound PAH were only 0 to 10% of the uptake of dissolved PAH. The potential for biotransformation has an important role in bioaccumulation by fish. Although accumulation of total radioactivity (PAH and metabolites) is 10-fold greater in fish exposed to BaP than in fish exposed to NPH, BaP is extensively metabolized whereas NPH is not. Consequently, the bioconcentration of the parent NPH greatly exceeds that of the parent BaP. Because more hydrophobic PAH, such as BaP, have a high affinity for binding to DHM and rapid rates of biotransformation, these interactions may act to mitigate the biological impact of those very hydrophobic PAH having the greatest potential for bioaccumulation and transfer to humans via food chains.