Thoughts on applying existing toxicological understanding to risk assessment for major ions in fresh waters

D. R. Mount, R.J. Erickson, B. Forsman, T.L. Highland, R. Hockett, D.J. Hoff, C.T. Jenson, T.J. Norberg-King, D.J. Soucek

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Recent research in our laboratories and many others have greatly increased understanding of the responses of freshwater organisms to increased concentrations of major geochemical ions (Na, K, Ca, Mg, Cl, SO4, HCO3) in laboratory toxicity tests, stream mesocosms, and in natu-ral streams. The lessons learned to date raise challenges to developing assessment approaches that effectively integrate knowledge from studies of all types. For example, studies of benthic community data from the field suggest that the conductivity associated with changes in those com-munities varies with the natural background in the study area, but it is not as clear how laboratory toxicity data should be viewed or applied with respect to varying background. Most laboratory toxicity studies involv-ing major ions are conducted using single salts (e.g., NaCl, MgSO4), but most exposures in natural waters involve elevation of multiple ions to varying degrees. As a specific example, how do we interpret toxicity data for MgSO4 alone at low Ca, when in the field elevated Mg usually co-occurs with at least some elevation of Ca as well? And further, how do we balance the practical appeal of guidelines based on single ions (e.g., Cl or SO4) with our understanding that toxicity is a function of the complete ionic composition of the water?
Original languageEnglish (US)
Title of host publication7th Society of Environmental Toxicology and Chemistry World Congress/Society of Environmental Toxicology and Chemistry North America 37th Annual Meeting, 6-10 November 2016, Orlando, Florida
StatePublished - 2016


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