Comparison of the toxicity of two chelated copper algaecides and copper sulfate to non-target fish.

New pesticide products are reviewed by the United States Environmental Protection Agency for possible effects to non-target aquatic organisms. The required toxicity data are for the active ingredient only, and fail to include toxicity of the mixture of other ingredients found in these pesticides. These ingredients may increase the toxicity of the active ingredient to non-target organisms. Our study compares the toxicity of two formulations of chelated copper algaecides with each other, and to a copper sulfate algaecide. We were particularly interested in the effects of a surfactant that is present in one of the formulations. We found that copper becomes less toxic to fish (e.g. fathead minnow 48-h LC50 = 0.90 mg/L) when it is chelated, providing an additional margin of safety to non-target fish compared to copper sulfate. However, inclusion of a surfactant to the formulation resulted in increased toxicity (e.g. fathead minnow 48-h LC50 = 0.30 mg/L).