Understanding the mechanism of ionic liquid toxicity to fish and Daphnia

I&EC 176

Aline Y. O. Matsuo, amatsuo@nd.edu and Gary A. Lamberti, glambert@nd.edu. Department of Biological Sciences, University of Notre Dame, 290B Galvin Life Sciences, Notre Dame, IN 46556-0369
The use of ionic liquids (ILs) as an environmentally friendly surrogate for traditional organic solvents in industry is very promising. However, because many ILs are highly soluble in water, aquatic organisms are highly susceptible to effects induced by these chemicals. Studies have shown that ILs are toxic to aquatic organisms ranging from bacteria to fish, and that toxicity is mostly attributed to the organic cation and its alkyl side-chains. Toxicity induced by ILs has been suggested to occur through narcosis, similar to effects reported for surfactants. In an effort to understand the possible modes of action of imidazolium and pyridinium-based ILs, we analyzed physiological responses in a crustacean ( Daphnia magna) and fish (Pimephales promelas and Danio rerio) exposed to ILs, based on ion uptake changes and by assessing disruption in membrane permeability. Water quality was also addressed during the experiments to understand whether the effects of IL toxicity was affected by hardness, dissolved organic matter content, pH, or temperature. The results are discussed and theories for the mechanistic toxicity of ILs are proposed.