Dietary accumulation and depuration of hydrophobic organochlorines: Bioaccumulation parameters and their relationship with the octanol/water partition coefficient

Abstract

Dietary accumulation of 23 hydrophobic organochlorines (OCs) by juvenile rainbow trout (Oncorhynchus mykiss) was studied with the objective of obtaining relationships between bioaccumulation parameters and the octanol/water partition coefficient (Kow). A wide range of OCs were used including 16 polychlorinated biphenyls (PCBs 18, 28, 44, 52, 66, 101, 105, 118, 128, 138, 153, 187, 189, 195, 206, and 209), hexachlorobenzene, mirex, tris(4-chlorophenyl)methane (TCPMe), tris(4-chlorophenyl)methanol (TCPMeOH), and three toxaphene congeners (Cl7-chlorobornane [CHB] [Hp-sed], Cl8-CHB [T2], and Cl9-CHB [T12]). Tris(4-chlorophenyl)methane (half-life [t1/2] = 65 d) was more persistent than TCPMeOH (t1/2 = 20 d), and TCPMe was not biotransformed to TCPMeOH by rainbow trout. Cl7-chlorobornane (t1/2 = 32 d) was more rapidly eliminated, and appears to be more readily metabolized, than Cl8-CHB (t1/2 = 43 d) and Cl9-CHB (t1/2 = 42 d). With the exception of TCPMeOH, Cl7-CHB, and PCB 18, all of the OCs had biomagnification factors (BMFs) >1, implying a potential to biomagnify. Half-lives had a significant curvilinear relationship with Kow (R2 = 0.85, p < 0.001), with a maximum t1/2 for OCs with log Kow ∼ 7.0. Decreasing t1/2 for OCs of log Kow > 7.0 may be related to slow kinetics of these super hydrophobic OCs and the short exposure phase, which results in insufficient time for the super hydrophobic OCs to reach slower clearing compartments of the rainbow trout. Assimilation efficiency was not as well described by Kow as by t1/2 and BMF, although a significant curvilinear relationship was observed (R2 = 0.53, p = 0.004). The BMF had a significant curvilinear relationship with log Kow (R2 = 0.84, p < 0.001). Recalcitrant OCs with a log Kow of ∼7.0 would appear to have the greatest potential for food chain biomagnification in fish.