Bioconcentration and metabolism of [14C]3-chloro-P-toluidine hydrochloride by Bluegill Sunfish

Bluegill sunfish (Lepomis macrochirus) were continuously exposed to 0.1 μg/ml of uniformly radiolabeled [14C]3‐chloro‐p‐toluidine hydrochloride (CPTH) for 28 d, after which the fish were transferred to flowing untreated water for a 28‐d depuration period. At periodic intervals during the treatment and depuration periods, samples of water and fish were analyzed for [14C] residues to determine the degree of CPTH absorption. Samples of bluegill that were exposed to the radiolabeled chemical for 28 d were analyzed to determine the distribution of the radiolabel and to isolate and identify possible metabolites. The steady‐state concentrations in the bluegill tissues were reached by day 7 of exposure to the radiolabeled compound, with mean concentrations in the edible, nonedible, and whole‐body tissues determined to be 2.9, 12.0, and 7.5 μg/g of tissue, respectively. Bioconcentration factors of 33×, 150×, and 88× were calculated for the three types of tissues. About 64% of the accumulated radiolabeled CPTH and metabolites were eliminated from the fish on day 28 of depuration. The distribution of radioactivity was found to be similar in all tissue groups. One metabolite was confirmed as N‐acetyl‐3‐chloro‐p‐toluidine, with two metabolites suggested to be 4‐acetamido‐2‐chlorobenzoic acid and 4‐amino‐2‐chlorobenzoic acid. The N‐acetylated breakdown product has been previously reported to occur in both mammals and birds; thus, the metabolism of CPTH in fish may parallel that observed in these other species. Although the effects of biomagnification cannot be fully assessed at this time, we can conclude that when bluegill sunfish are continuously exposed to sublethal levels of CPTH, bioconcentration will not occur to an appreciable extent, and that residues will be rapidly excreted upon removal of the fish from the CPTH source. Furthermore, published information pertaining to various aquatic organisms indicates that bioaccumulation will not be a problem if the bioconcentration factor is below 100.