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Ecotoxicological information

Short-term toxicity to fish

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Description of key information

The highest concentration causing no mortality (no observed effect concentration, NOEC) after 96 hours was estimated to be 8.65 mg/L, whereas 100  % mortality was produced within 18 hours at about 31.2 mg/L. The LC50 (96 h) was estimated to be 18.85 mg/L.
The waiver included as separate endpoint study record further gives reference to an assessment made on altogether 28 organic peroxides demonstrating that among the three trophic levels, the alga proved to be the most sensitive species under short-term conditions to organic peroxides.
In consequence, a new test on short-term toxicity to fish is not required.

Key value for chemical safety assessment

LC50 for freshwater fish:
18.85 mg/L

Additional information

Tert-butyl peroxypivalate was tested in an acute toxicity test with Brachydanio rerio (zebra fish) under semi-static conditions according to EU method C.1 and OECD guideline no. 203. No chemical analyses of the test substance dissolved in the test media were performed. Therefore, all concentrations referred to in the report are nominal concentrations. The highest concentration causing no mortality (no observed effect concentration, NOEC) after 96 hours amounted to 13.3 mg/L, whereas 100 % mortality was produced within 18 hours at 48 mg/L. The LC50 (96 h) was calculated to be 29.0 mg/L with 95 % confidence limits of 23.3 and 36.1 mg/L. At 25.3 mg/L and higher concentrations reduced activity could be observed starting after 1-3 hours and lasting throughout the test. At 48 mg/L and 91.2 mg/L disturbances and loss of equilibrium were observed before the fish died.

As mentioned before these are the results based on nominal concentrations as the test has been performed without chemical analyses. However, based on the hydrolytical instability of the substance (see section 5.1.2 for details), this degradation will lower the effect concentrations NOEC and LC50 and has to be taken into consideration. Since the two other acute toxicity studies performed with Daphnia (see IUCLID5 section 6.1.3) and Algae (see IUCLID5 section 6.1.5.) have been performed including chemical analyses, the recovery rates on measured concentrations obtained in these studies have been used as reference. As a worst case approach a concentration of 65 % of the nominal value was assessed which is equal to the lowest concentration measured in the acute test with Daphnia magna. Application of this 65 % recovery rate to the nominal effect concentrations determined in the fish study leads to a reduction of the NOEC (96h) to ca. 8.65 mg/L and LC50 (96 h) to ca. 18.85 mg/L.

As compared to the acute toxicity studies with Daphnia and Algae the fish is far from being the most sensitive species in this aquatic toxicity studies.

This is further supported by an assessment on the most sensitive species for organic peroxides, which has been made by the member of the organic peroxides consortium and which is referred to in a waiver additionally added as a separate endpoint study record in this section.

The most critical acute data available for each trophic level (aquatic invertebrates, fish and algae) for altogether 28 organic peroxides belonging to the group of organic peroxides registered under REACH had been compiled in order to determine the species sensitivity for the organic peroxides. In conclusion, among the three trophic levels, the alga proved to be the most sensitive species under short-term conditions to organic peroxides (for details see the organic peroxides consortium’s position paper “Adaption of the Assessment Factor for Aquatic PNEC Derivation for Organic Peroxides - Low acute to chronic ratio” (author: CEHTRA, Report no. CFR-12.012, cf. attachment in IUCLID section 13). Thus, even though the analytical investigations are missing in the short-term toxicity test to fish, due to animal welfare reasons a repetition of this vertebrate study is not foreseen as not reasonable.

Thus, even though the analytical investigations are missing the test available is considered sufficient to evaluate the short-term toxicity to fish. Further, due to animal welfare reasons a repetition of this vertebrate study is not foreseen as not reasonable.