Dietary accumulation and quantitative structure-activity relationships fordepuration and biotransformation of short (C-10), medium (C-14), and long (C-18) carbon-chain polychlorinated alkanes by juvenile rainbow trout (Oncorhynchus mykiss)

Juvenile rainbow trout (Oncorhynchus mykiss) were exposed to three [C-14]-p olychlorinated alkanes (PCAs) (C10H15.3Cl6.7 C14H23.3Cl6.7, and C18H31.4Cl6 .6) at nominal concentrations of 1.5 and 15 mu g/g for 40 d, followed by 16 0 d of clean food, to measure bioaccumulation parameters and biotransformat ion. These PCAs are identical in carbon-chain length and chlorine content t o industrial chlorinated paraffin products, although their method of synthe sis differs from that of chlorinated paraffin products. Half-lives ranged f rom 26 to 91 d, biomagnification factors ranged from 0.9 to 2.8, and both e xhibited increasing trends with increasing carbon-chain length. Data from t his work and others on PCAs were used to determine biotransformation rates and to examine quantitative structure-activity relationships for bioaccumul ation 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 K-ow. The PCA biotransformation rates (p er day) ranged from -0.00028 to 8.4 and exhibited negative relationships wi th the number of carbon atoms, of chlorine atoms, of total carbon and chlor ine atoms, and log K-ow. Results suggest that PCAs with a total number of c arbon and chlorine atoms between 22 and 30 are slowly, or are not, biotrans formed in juvenile rainbow trout. Increasing carbon-chain length and chlori ne 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 chlorinat ed PCAs indicate that information is needed regarding the environmental con centrations of these PCAs in aquatic food chains.