Determination of hazardous concentrations of 2,4-dinitrophenol in freshwater ecosystems based on species sensitivity distributions

2,4-dinitrophenol (2,4-DNP) is a phenolic compound used as a wood preservative or pesticide. The chemical is hazardous to freshwater organisms. Although 2,4-DNP poses ecological risks, only a few of its aquatic environmental risks have been investigated and very limited guidelines for freshwater aquatic ecosystems have been established by governments. This study addresses the paucity of 2,4-DNP toxicity data for freshwater ecosystems and the current lack of highly reliable trigger values for this highly toxic compound. We conducted acute bio-assays using 12 species from nine taxonomic groups and chronic assays using five species from four taxonomic groups to improve the quality of the dataset and enable the estimation of protective concentrations based on species sensitivity distributions. The acute and hazardous concentrations of 2,4-DNP in 5% of freshwater aquatic species (HC5) were determined to be 0.91 (0.32-2.65) mg/L and 0.22 (0.11-0.42) mg/L, respectively. To the best of our knowledge, this is the first report of a suggested chronic HC5 for 2,4-DNP and it provides the much-needed fundamental data for the risk assessment and management of freshwater ecosystems.