2,4-dinitrophenol (2,4-DNP) is a harmful chemical found in wood preservatives and pesticides that can harm freshwater organisms. A study was done to figure out how much of this chemical is dangerous to aquatic species. They tested 12 species in short-term tests and 5 species in long-term tests. The results showed that 0.91 mg/L of 2,4-DNP is harmful to 5% of freshwater species in short-term exposure, and 0.22 mg/L is hazardous in the long term. This information helps us understand the risks of 2,4-DNP to freshwater ecosystems.