What Is the 6PPP-Quinone Concentration That Is Protective for Coho Salmon?

The USEPA developed an Aquatic Life Screening Value (ASLV) of 11 ng/L for 6PPD Quinone (6PPD-Q), a breakdown product of 6PPD, an antiozonant in automobile tires. Because some coho populations are listed, “Take” requires that no individuals be harmed. The question asked in the present study is whether the ASLV for 6PPD-Q is protective for coho salmon. To answer this question, a concentration–response regression was developed for juvenile coho salmon from the raw data used to generate the three published acute mortality studies. The % mortality from the ASLV was read from the concentration–response regression resulting in a mean predicted mortality (95% confidence limits) of 2% (1–14%). Because of the Take restriction on harming a threatened or endangered species, the protective concentration of 6PPD-Q in coho-bearing streams should be set below the concentration–response curve. The LC1 and 95% CL are 8.5 (1.3–17.8) ng/L. The lower CL is 8.5 times lower than the EPA ASLV. A concentration of 6PPD-Q that does not result in mortality of one individual coho salmon should be below the lower 95% CL of the LC1 (approximately 1 ng/L). Results of this study show that the EPA ASLV is not protective for coho.