Derivation of predicted no effect concentrations (PNEC) for 2,4,6-trichlorophenol based on Chinese resident species

2,4,6-Trichlorophenol (2,4,6-TCP) is a common chemical intermediate and a by-product of water chlorination and combustion processes, and is a priority pollutant of the aquatic environment in many countries. Although information on the toxicity of 2,4,6-TCP is available, there is a lack of information on the predicted no-effect concentration (PNEC) of 2,4,6-TCP, mainly due to the shortage of chronic and site-specific toxicity data. In the present study, acute and sub-chronic toxicity of 2,4,6-TCP on six different resident Chinese aquatic species were determined. PNEC values were calculated and compared by use of two approaches: assessment factor (AF) and species sensitivity distribution (SSD). Values for acute toxicity ranged from 1.1 mg L(-1) (Plagiognathops microlepis) to 42 mg L(-1) (Corbicula fluminea) and the sub-chronic no observed effect concentrations (NOECs) ranged from 0.05 mg L(-1) (Mylopharyngodon piceus) to 2.0 mg L(-1) (C. fluminea). PNECs obtained by the assessment factor approach with acute (AF=1000, 0.001 mg L(-1)) or chronic (AF=10, 0.005 mg L(-1)) toxicity data were one order of magnitude less than those from SSD methods (0.057 mg L(-1)). PNEC values calculated using SSD methods with a 50% certainty for 2,4,6-TCP was less than those obtained by use of the USEPA recommend final chronic value (FCV) method (0.097 mg L(-1)) and the one obtained by use of the USEPA recommend acute-to-chronic (ACR) methods (0.073 mg L(-1)). PNECs derived using AF methods were more protective and conservative than that derived using SSD methods.