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Acute toxicity and toxicokinetics of 4‐heptylphenol in juvenile atlantic cod (Gadus morhua L.)

Heptylphenol has been detected in produced water from various oil production platforms in the Norwegian sector of the North Sea and may be of environmental concern due to hydrophobic properties and slow biodegradation in the marine environment. The n‐octanol/water partition coefficient of 4‐heptylphenol (4‐HP) was estimated by a high‐performance liquid chromatographic correlation analysis. Acute toxicity and toxicokinetics of 4‐HP in juvenile Atlantic cod (Gadus morhua L.) were investigated in flow‐through exposure systems using unlabeled and 14C‐labeled 4‐HP, respectively. The results show that 4‐HP was moderately hydrophobic (log Kow = 4.5) and toxic to juvenile cod (96 h LC50 = 2.9 μmol/L). The toxicokinetics of 4‐HP was calculated using a one‐compartment first‐order kinetic (1CFOK) model (k1 = 29.94 ± 1.83, k2 = 0.052 ± 0.011/h, t95 ≈ 58 h and t1/2 ≈ 13 h). The values obtained corresponded to a steady‐state and kinetic bioconcentration factor (BCF) of 555 and 578, respectively. The distribution pattern of 4‐HP (and/or metabolites) at steady state and after 96 h of recovery in uncontaminated seawater was dominated by the gastrointestinal system possibly owing to biotransformation and elimination through these organs. The results also revealed that neither 4‐HP nor possible metabolites bind to macromolecules or tissue structures in the fish.