Dietary accumulation and quantitative structure‐activity relationships for depuration and biotransformation of short (C10), medium (C14), and long (C18) carbon‐chain polychlorinated alkanes by juvenile rainbow trout (Oncorhynchus mykiss)

Juvenile rainbow trout (Oncorhynchus mykiss) were exposed to three [14C]-polychlorinated alkanes (PCAs) (C10H15.3Cl6.7, C14H23.3Cl6.7, and C18H31.4Cl6.6) at nominal concentrations of 1.5 and 15 μg/g for 40 d, followed by 160 d of clean food, to measure bioaccumulation parameters and biotransformation. These PCAs are identical in carbon-chain length and chlorine content to industrial chlorinated paraffin products, although their method of synthesis differs from that of chlorinated paraffin products. Half-lives ranged from 26 to 91 d, biomagnification factors ranged from 0.9 to 2.8, and both exhibited increasing trends with increasing carbon-chain length. Data from this work and others on PCAs were used to determine biotransformation rates and to examine quantitative structure-activity relationships for bioaccumulation and biotransformation. Quantitative structure-activity relationships developed for half-life and biomagnification factor showed positive linear relationships with the number of carbon atoms, of chlorine atoms, of total carbon and chlorine atoms, and log Kow. The PCA biotransformation rates (per day) ranged from −0.00028 to 8.4 and exhibited negative relationships with the number of carbon atoms, of chlorine atoms, of total carbon and chlorine atoms, and log Kow. Results suggest that PCAs with a total number of carbon and chlorine atoms between 22 and 30 are slowly, or are not, biotransformed in juvenile rainbow trout. Increasing carbon-chain length and chlorine content result in greater bioaccumulation of PCAs by reducing partition-based (i.e., diffusion) and metabolic (i.e., biotransformation) elimination processes. High bioaccumulation potential and low biotransformation rates of medium (C14-18) and long (C18-30) carbon-chain PCAs and highly chlorinated PCAs indicate that information is needed regarding the environmental concentrations of these PCAs in aquatic food chains.

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