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Short-term toxicity to aquatic invertebrates

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Description of key information

Based on a number of published studies, the acute toxicity of NPE-2, NPE-1.5 and NPE-1 lie in the range of 0.11 to 0.716 mg/L. The lowest presented 48 h LC50 of 0.148 mg/L from a study in Daphnia with NPE-2 was selected as a conservative value for NPEO.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates
Effect concentration:
0.148 mg/L

Additional information

A study was conducted to evaluate the acute toxicity of a commercial nonylphenol ethoxylate formulation with an average ethoxylation grade of 2 (NPE-2) to Daphnia magna after 48 h exposure. Five 24 h neonates were added to 10 ml of hard water containing the test substance. The tests were carried out twice. Ten Daphnia were used for each sample concentration and the study vessels were kept at 20°C in the dark. The number of surviving Daphnia was counted after 48 h and LC50 values were derived with Probit analysis. No analytical dose verification was reported. Under the test conditions, the LC50 for Daphnia magna was determined to be 0.148 mg/L (Maki H et al., 1998).

A study was conducted to evaluate the acute toxicity of pure NPE-2 to Cerodaphnia dubia under semi-static conditions in dechlorinated freshwater. The procedures followed EPA Guideline 600/4-90/027F. Less than 24 h oldCeriodaphniawere exposed to the test substance at measured concentrations of<12.2 (control),274 ± 35, 489 ± 41, 839 ± 83, 1,800 ± 80 and 3,640 ± 4 µg/L for 48 h.Four replicates were used per dose group,with each beaker containing five organisms. Organisms were not fed during the test and observed daily for mortality. The study included a negative control (plain stock solution and a positive control (potassium chloride).Test substance concentrations were verified analytically using HPLC on water samples collected from each of the new exposure concentrations at 0 and 24 h. At 24 and 48 h, the four replicates of the old exposure concentrations were combined and the composites were sampled.Survival in the controls was ≥90% and the result from the reference substance test was found to be within acceptable limits.Guideline water quality criteria were met. Under the test conditions, the 48 h LC50 for Ceriodaphnia dubia was 716 µg (0.716 mg)/L (TenEyck MC and Markee TP, 2007).

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

NPE-1 measured concentrations were equivalent to <10.4 (control), 27.4 ± 1.9, 53.9 ± 5.6, 114 ± 12, 221 ± 25 and 486 ± 28 µg/L. The 96 h LC50 was 328 µg (0.3288 mg)/L.

A study was conducted to evaluate the acute toxicity of NPE-2 (99% pure) to Daphnia magna under static conditions in freshwater. Daphnia (10 neonates per vessel) were exposed to the test substance at five different concentrations (test concentrations not stated) and to one solvent control for 24 h. Each concentration was replicated. The organisms were not fed during the study and mortality was observed after 24 h. Analytical verification of doses was not reported. Under the test conditions, the 24 h LC50 forDaphnia magnawas determined to be 0.56 mg/L (Sun H and Gu X , 2005).

A study was conducted to evaluate the acute toxicity of a highly branched tripropylene (tp-) NPE-1.5 (99% pure) to the estuarine crustacean Mysidopsis bahia under semi-static (24 h renewal) conditions in saltwater. The procedures followed EPA Guideline OPP 72-2. Three to eight day old Mysidopsis bahia were exposed to NPE-1.5 at different concentrations (values not specified) for 48 h. Doses were verified analytically. All toxicant exposures consisted of two replicates with four organisms per concentration whereas controls consisted of four replicates with four organisms each. A negative control (aged, natural saltwater) and a positive control (NPE-9) were also included in the study. Under the test conditions, the 48 h LC50 for Mysidopsis bahia was 0.11 mg/L (Hall WS et al., 1989).