Critical review of proposed residue-based selenium toxicity thresholds forfreshwater fish

Proposed fish toxicity thresholds for interpreting the biological significa nce of selenium concentrations measured in environmental media include 2 to 5 mu g/L in water, 4 mg/kg dw in fish whole body tissue, 10 mg/kg dw in fi sh ovaries, and 3 mg/kg dw in fish diets. Use of these thresholds would lik ely identify fish populations as being at risk at numerous sites across the U.S. However, selenium effects on fish populations in the field have only been conclusively demonstrated at a few locations. Based on our critical re view, these threshold values are not consistent with USEPA methodology for deriving criteria, in many cases are not supported by the scientific litera ture, and, as a result, are generally overly conservative. Based on current ly available information, we believe the scientific literature is not suppo rtive of generic sediment or water thresholds, but is supportive of alterna tive separate whole body thresholds of 9 mg/kg dw for warmwater fish and 6 mg/kg dw for larval coldwater anadromous fish, an ovary threshold of 17 mg/ kg dw for warmwater fish, and fish dietary thresholds of 10 and 11 mg/kg dw for warmwater fish and larval coldwater anadromous fish, respectively.