Dietary accumulation of C12‐ and C16‐chlorinated alkanes by juvenile rainbow trout (Oncorhynchus mykiss)

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Abstract
Dietary exposures using juvenile rainbow trout (Oncorhynchus mykiss) were conducted with four 14C‐polychlorinated alkanes (C12H20Cl6 [56% Cl by weight], C12H16Cl10 [69% Cl], C16H31Cl3 [35% Cl], and C16H21Cl13 [69% Cl]) in order to measure bioaccumulation parameters, metabolism, and tissue distributions. These chlorinated alkanes are found in industrial chlorinated paraffin (CP) products, although their method of synthesis is different than that of CPs. Trout were exposed for 40 d to nominal concentrations of 20 and 200 ng/g of each chlorinated alkane, as well as to 2,000 ng/g for C16H21Cl13, followed by an elimination period of up to 173 d. Whole‐body half‐lives in the rainbow trout ranged from 37 ± 2 d for C16H31Cl3 to 87 ± 11d for C12H16Cl10, and assimilation efficiencies of C16H31Cl3 (33 to 35%) and C12H16Cl10 (34 to 38%) were highest among the four alkanes. Biomagnification factors ranged from 0.44 for C16H21Cl13 to 2.15 for C12H16Cl10. Accumulation of C16H21Cl13 (molecular weight = 674) may be sterically hindered due to its large molecular size. Lower chlorinated alkanes, e.g., C16H31Cl3, had shorter half‐lives than highly chlorinated alkanes, probably due to increased metabolism. High‐performance liquid chromatography 14C analysis offish tissue extracts revealed that the chlorinated alkane mixtures were selectively biotransformed with certain unknown components persisting in tissues. Lower chlorinated alkanes had greater proportions of polar 14C, which implies greater metabolism of these compounds. Highly chlorinated, short‐carbon‐chain (C10–13) alkanes and lower chlorinated, medium‐carbon‐chain (C14–18) alkanes appear to have the greatest potential for biomagnification among CP components. No reduced growth rates or hepatic monooxygenase enzyme induction were seen in any of the chlorinated alkane exposures when compared with controls.