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Ecotoxicological information

Long-term toxicity to fish

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Description of key information

Chronic toxicity studies have been conducted with several pure or commercial NP ethoxylates and with NP alone. The data suggest that toxicity increases as the ethoxylation grade decreases. The NOEC was 0.006 mg/L in a Fish Early Life Stage study in trout with NP.

Key value for chemical safety assessment

EC10, LC10 or NOEC for freshwater fish:
0.006 mg/L

Additional information

A study was conducted to evaluate the effects NPE-1 (high purity experimental preparation from Huntsman Corporation) on growth and survival of the Japanese medaka (Oryzias latipes). Medaka were exposed to the test substance for 100 days post-hatch under semi-static conditions (renewed every 48 h) at nominal concentrations of 0, 0.010, 0.030, 0.100 and 0.300 mg/L (equivalent to measured concentrations of 0, 0.0035, 0.0105, 0.035 and 0.105 mg/L), with acetone as vehicle. A concentration of 1.0 mg/L was also tested but excluded because 100% mortality occured within the first week of exposure. Two negative controls (acetone and clean control) and a positive control (1 µg/L 17β- estradiol (E2)) were run in parallel for validation purposes. Exposure was initiated with 150 fry per concentration. Survival and growth were monitored in each treatment after the first and second month of exposure and after 100 days. Fifty randomly chosen fish from each treatment were sacrificed at the end of the test for assessment purposes. The fish were also monitored for alterations to sex ratio, secondary sex characteristics and development of gonadal intersex (i.e. testis–ova) but these potentially endocrine-mediated effects are not considered in this section. They are discussed below in Chapter 7.6. There were no significant effects on growth and survival at any dose, so the 100 d NOEC for these endpoints could be considered to be 0.105 mg/L (measured) (Balch G and Metcalfe C, 2006).

In the same study, the authors tested the effects of NP and NPE-4 under comparable experimental conditions.

NP (HP-PNP) exposure occurred at nominal concentrations of 0, 0.001, 0.003, 0.010, 0.030 and 0.100 mg/L (equivalent to measured concentrations of 0, 0.00029, 0.00087, 0.0029, 0.0087 and 0.029 mg/L). Survival and growth were not affected at any dose (100 d NOEL: 0.029 mg/L, measured).

NPE-4 (Surfonic®N40) exposure occurred at nominal concentrations of 0, 0.010, 0.030, 0.100, 0.300 and 1.0 mg/L (equivalent to measured concentrations of 0, 0.0038, 0.0114, 0.038, 0.114 and 0.380 mg/L). Survival and growth were not affected at any dose. The 100 d NOEL for the study was therefore equivalent to 0.380 mg/L (measured).

In a Fish Early-life Stage Toxicity Test conducted according to EPA Guideline OPPTS 850.1400, the effects of NP on early lifestage development (egg hatchability, survival, and growth) of Rainbow trout (Oncorhynchus mykiss)after 91 d of exposure (flow-through) were examined. The measured concentrations of NP used in the study were 6.0± 2.5, 10.3± 5.4, 23.1± 5.8, 53.0± 12.7and 114± 21.5µg/L. Hatching of rainbow trout eggs occurred approximately 34 d after fertilization and hatching success was not significantly affected at any of the tested levels. Mortality of larvae at the two highest concentrations was 95.5 and 100%, respectively, by 3 d posthatch. No larvae survived to the end of the test in these groups. Mortality began by 8 d posthatch at 23.1 µg/L and approximately 67% of the fish died by the end of the test. Mortality was not significantly different from the control at lower concentrations, with over 90% of the larvae surviving to the end of the test. Growth, as measured by mean standard length, wet weight and dry weight of larvae at test termination, was significantly lower than for controls at 10.3 µg/L and higher. No significantly different effects from control (p ≤ 0.05) were observed at 6.0 µg/L. The NOEC and LOEC for the study were therefore 6.0 and 10.3 µg (0.006 and 0.0103 mg)/L, respectively. The EC20 calculated from the concentration response curve for biomass (% survival x weight) was 8.4 µg (0.008 mg)/L. The acute to chronic ratio (EC50/chronic value) for rainbow trout and NP was 13.8 (Spehar RLet al., 2010).