Work supported by research grants NSF-GH33634 and NSF-GI-31605-IES-7. Mention of commercial products is for identification only and does not constitute endorsement by any agency of the U.S. Government.

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Some hydrophobic chemicals may reach plateau levels in fish only after several months of continuous exposure. Therefore, an accelerate•l test procedure, based on kinetics, was developed using an isomer of PCB's (polychlorinated biphenyls): 2,2',4,4'-tetrachlorobiphenyl. The rates of uptake and clearance of 2,2',4,4'•tetrachlorobiphenyl were determined by analysis of rainbow trout (Salmo gairdneri Richardson). These trout were exposed to 1.6 and 9.0 gg/liter for five days and then transferred to fresh water. A nonlinear regression analysis was used to estimate the rate constants for uptake and clearance, and the bioconcentration factor at steady-state was calculated from the rate constants. For 2,2',4,4'-tetrachlorobiphenyl, the bioconcentration factor at steady-state was 9550 q-1610 in trout muscle.The accuracy of the bioconcentration factor determined by this accelerated test procedure was compared with experimental observations in a 42-day test. The concentration of 2,2',4,4'-tetrachlorobiphenyl in trout muscle was 82 ___ 20/•g/g after 42 days continuous exposure to 14/•g/liter. This was in good agreement with 92 q-18 /•g/g predicted from the accelerated procedure. The 42-day level was about 43% of the theoretical steady-state for 2,2',4,4'•tetrachlorobiphenyl in trout muscle. Therefore, this accelerated procedure can provide information about the potential of a chemical to bioconcentrate in fish in a much shorter period of time than can be provided by previously described methods.The objective of this investigation was the development of an accelerated test procedure for measuring the bioconcentration potential of chemicals in fish. The bioconcentration factor is expressed as the ratio of the concentration in the fish (at steady-state) to the

The uptake and depuration rate constants for ['4C]2,3,7,8-tetrachlorodibenzo-p-dioxin ("C-TCDD) in growing rainbow trout were obtained in a laboratory experiment involving a 6-h static water uptake exposure at 107 ng/L @pt) followed by a 139-d flow-through depuration period. Improved mathematics were developed for estimating uptake and depuration rate constants and an equilibrium bioconcentration constant that accounts for growth dilution of the total chemical body burden. The uptake and depuration rate constants ( k ; and k2) for I4C-TCDD in rainbow trout (whole fish) were determined to be 108 f 3 ml water/g whole fish/d and 0.012 f 0.001 d-', respectively. Based on these data, the equilibrium bioconcentration constant for TCDD, defined as the ratio of uptake to depuration rate constants, was 9,270 f 1,050, and the elimination halflife, of the total body burden was 58 f 5 d. Clinical observations of the fish concurred with those previously reported by other researchers.

The toxicity of three samples of pentachlorophenol (PCP) containing various impurities was evaluated in 90‐d, partial life‐cycle toxicity studies with fathead minnows (Pimephales promelas Rafinesque). Samples of purified PCP, Dowicide EC‐7, and a composite of commercial PCP were used in the studies. The exposure concentrations were 10 to 142 μg/L of the purified PCP; 8 to 139 μg/L of the Dowicide EC‐7; and 6 to 121 μg/L of the commercial composite of PCP. The purified PCP contained relatively high amounts of chlorinated phenoxyphenols; Dowicide EC‐7 contained more types of impurities, but generally at lower concentrations than in either the purified PCP or the commercial composite; and the commercial composite contained relatively large quantities of hexachlorobenzene, chlorinated phenoxyphenols, chlorinated dibenzodioxins, and chlorinated dibenzofurans. Concentrations of the purified PCP equal to or greater than 85 μg/L reduced the growth of the fathead minnows but did not adversely affect survival. Dowicide EC‐7 concentrations as high as 139 μg/L did not adversely affect growth or survival of fathead minnows. The commercial composite of PCP reduced growth at concentrations of 13 μg/L or higher and reduced survival at concentrations of 27 μg/L or higher. Degeneration of the fins and opercles, and malformations of the anterior regions of the skull were also noted in fathead minnows exposed to the commercial composite of PCP. Impurities clearly increased the toxic effects of PCP in fathead minnows.