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Reliable shot-term (acute) and long-term (chronic) aquatic toxicity test data are available for this substance for the three principle trophic levels: primary producers, represented by algae; plant eating animals, represented by daphnids; and predators, represented by fish. In addition, results from an activated sludge respiration inhibition study are also available. These studies were conducted at concentrations near or above the water solubility limit for this substance which is very low (0.4 µg/L). None of the short-term or long-term aquatic toxicity studies exhibited toxic effects at the limit of water solubility (i.e., NOEC > water solubility). For the primary producer trophic level an OECD Guideline 201 algal growth inhibition study was conducted under GLP. In this study no inhibition of growth or biomass was observed at the highest measured test concentration of 0.86 mg/L (NOEC ≥0.86 mg/L), which is several orders of magnitude above the water solubility limit. Short-term acute toxicity studies with three different species of invertebrates have been conducted. A pre-GLP 96-hour acute toxicity test was conducted with planorbid snails (H. trivolvis) at nominal concentrations up to 984 mg/L under static conditions. There was no mortality or abnormal effects observed at 984 mg/L (NOEC ≥984 mg/L).  A 48-h static acute OECD 202 toxicity limit test conducted withDaphnia magna under GLP resulted in a NOEC of ≥ 1.4ug/L.   Eastern oysters (C. virginica) in a 96-h acute toxicity study, were exposed at measured concentrations of 0, 30.3, 168, and 624 µg/L under flow-through conditions. There was no mortality or inhibition in shell deposition observed at any of the exposure concentrations during this study.  The 96-h NOEC value was ≥ 624 µg/L, the highest concentration tested. 

 Long-term (chronic) toxicity to invertebrates was evaluated in a 21-d study utilizing Daphnia magna. The organisms were exposed at measured concentrations up to 0.76 µg a.i./L under flow-through conditions. No differences in survival, growth (length and/or dry weight), or reproduction (cumulative young produced) was observed among organisms in this study. The 21-d NOEC value was ≥0.76 µg a.i./L for this study. 

Short-term (acute) toxicity to fish was evaluated using two different species. A pre- GLP 96-h acute toxicity was conducted utilizing fathead minnows (P. promelas). The organisms were exposed at nominal concentrations of 0, 98.4, and 984 mg/L under static conditions.  There was no mortality or abnormal effects observed at 984 mg/L (1000 uL/L), the highest exposure concentration during this study. The 96 -h NOEC value was ≥ 984 mg/L.  A second study under GLP was conducted with Rainbow trout (O. mykiss). In that 7-day acute toxicity study, the organisms were exposed at measured concentrations of 0, 0.013, 0.021, 0.038, 0.080, and 0.25 mg/L under flow-through conditions. There was no mortality or abnormal effects observed at any of the exposure concentrations during this study.  The 7-day NOEC value was 0.25 mg/L, the highest concentration tested. 

Long-term (chronic) toxicity to fish was evaluated in a 71-d toxicity study with rainbow trout. Eggs and fry were exposed at measured concentrations up to 0.28 mg/L under flow-through conditions. No differences in hatchability, survival, or growth (standard length and/or wet weight) were observed among organisms in this study.  The 60-day post-hatch NOEC value was >= 0.28 mg/L. 

Sewage sludge microorganisms were exposed in a 3-hour toxicity study at nominal concentrations of 0, 0.1, 0.3, 1.0, 3.2, and 10 mg/L under static conditions. There was no inhibition of respiration rate observed at any of the exposure concentrations during this study.  The 3-hour NOEC value was ≥ 10 mg/L, the highest concentration tested. The substance is not expected to inhibit respiration of secondary waste treatment microorganisms.