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Short-term toxicity to fish

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Description of key information

Studies were conducted to evaluate the acute toxicity of NP, NPE-1 and NPE-2 to fathead minnow (Pimephales promelas) under flow-through conditions in freshwater. The procedures followed EPA guidelines. Under the test conditions, the 96 h LC50 values were 0.136, 0.218 and 0.323 mg/L, respectively. The data suggests that the acute toxicity to fish decreases as ethoxylation grade increases, as would be expected based on water solubility. The 96 h LC50 of 0.218 mg/L for Pimephales promelas exposed to NPE-1 was selected as being representative for NPEO (which contains > 30 - <50% NPE-1).

Key value for chemical safety assessment

LC50 for freshwater fish:
0.218 mg/L

Additional information

A study was conducted to evaluate the acute toxicity of pure NPE-2 to fathead minnow (Pimephales promelas) under flow-through conditions in dechlorinated freshwater. The procedures followed the EPA Guideline OPP 72-1. After an acclimatisation period of 24 h, less than 4 day old fish larvae were exposed at the measured concentrations of <12 (control),99.4 ± 37.2, 129 ± 43, 188 ± 47, 287 ± 75 and 630 ± 150µg/L for 96 h. Four replicates were used for each dose group. Test substance concentrations were verified analytically using HPLC on water samples collected from the middle of the exposure tanks at 0 and 96 h and from half of the tanks at 24, 48 and 72 h. The animals were not fed during the test and were observed daily for mortality. Corresponding potassium chloride reference tests were conducted and found to be within acceptable limits. Survival in the controls for all of the replicates was >95% and the guideline water quality criteria were met. Under the study conditions, the 96 h LC50 for Pimephales promelas was 323 µg (0.323 mg)/L (TenEyck MC and Markee TP, 2007).

In the same study, the authors also tested pure NPE-1 and NP under similar conditions.

NPE-1 measured concentrations were equivalent to <10.4 (control), 39.4 ± 15.3, 51.4 ±15.3, 88.7 ± 22.8, 164 ± 31 and 338 ± 10 µg/L. The 96 h LC50 was 218 µg (0.218 mg)/L.

NP measured concentrations were <3.1 (control), 19.3 ± 3.1, 24.9 ± 6.3, 36.5 ± 7.3, 88.7 ± 5.7 and 229 ± 19 µg/L. The 96 h LC50 was 136 µg (0.136 mg)/L.