Acute Toxicities of Three Para-Phenylenediamine Quinones to Coho Salmon (Oncorhynchus kisutch) Juveniles and Embryonic Cells

The acute toxicities of para-phenylenediamine quinones (PPDQs) to salmonids at the whole-organism level remain unclear. Therefore, in this study, we investigated the acute toxicities of three PPDQs, 6PPDQ, 7PPDQ, and 8PPDQ in coho salmon ( Oncorhynchus kisutch ) juveniles and embryonic cells (CSE-119) using 24-h acute toxicity tests and cytotoxicity assays. The 24-h 50% effect concentration values of 6PPDQ and 7PPDQ for the juveniles were 41.5 ng/L (95% confidence interval: 21.6–61.4) and 5.39 μg/L (2.26–8.53), respectively, while 8PPDQ did not affect mortality at the tested concentration (60.6 μg/L). Further, the 24-h 50% effect concentration value of 6PPDQ for CSE-119 was 14.9 μg/L (13.0–16.7), but 7PPDQ and 8PPDQ did not sufficiently reduce CSE-119 cell viability even at concentration up to 500 μg/L, indicating marked differences in toxicity among the compounds. These findings indicate that, at both the whole-organism and cellular levels, 6PPDQ exhibited the highest toxicity among the three PPDQs, likely due to differences in chemical structure.