Toxicokinetics and biotransformation of pentachlorophenol in the topsmelt (Atherinops affinis)

The toxicokinetics and biotransformation of pentachlorophenol (PCP) were determined in the topsmelt (Atherinops affinis) In a static system, topsmelt (n = 9) were exposed to 50 μg/L of U-¹⁴C]PCP for 24 hours to determine the absorption rate constant (Ka), the whole-body bio-concentration (at steady-state conditions), the elimination rate constant UQ, and the elimination half-life (t_1/2). Kinetics were determined by direct quantitation of radioactivity in the exposure water. Following exposure, fish were placed in a flow-through metabolism chamber for 24 hours to allow depuration of retained residues, which were collected on XAD-4 resin. Excreted residues were identified and quantified by high-pressure liquid co-chromatography, fraction collection, and liquid scintillation counting. The Ka and Ke, calculated using a simplified model, were 0.012 M-1 0.005/h and 0.014±;0.003/h, respectively, while the 24 hour total concentration factor was 278.0×182.0 and the t_1/2 was 52.7±;11.2. During 24 hours of exposure to dean seawater, topsmelt depurated 32.9% of retained residues, and while PCP was primarily excreted unchanged (64.9%), significant amounts of both pentachlorophenylsulfate (18.9%) and pentachloro-β-D-glucuronide (16.2%) were also formed.