Registration Dossier

Ecotoxicological information

Endpoint summary

Administrative data

Description of key information

Additional information

Acute toxicity to fish:

The acute toxicity of the test item to fish (zebrafish) was determined according to the OECD Guideline 203, EU Council Regulation No. 440/2008 method C.1 and EPA OPPTS 850.1075. A semi-static test was performed as a limit test with a concentration of 100 mg/L. The test item solution was prepared by mechanical dispersion – 0.5 g test item were dissolved in 5000 mL ISO Medium. Ten test organisms were exposed to the test concentration and the control, respectively, for 96 hours. The measured concentration of the test item at the start of the renewal periods was 1.2 mg/L and at the end of the renewal periods was 0.6 mg/L, respectively. The limit concentration of the test item was found to have no effect on the vitality of zebrafish. In conclusion, the NOEC corresponds to the nominal concentration 100 mg/L (0.9 mg/L measured geometric mean concentration). The LC50 and the LC100 correspond to the nominal concentration >100 mg/L (>0.9 mg/L measured geometric mean concentration).

Acute toxicity to aquatic invertebrates:

The acute toxicity of the Water Accommodated Fraction (WAF) of 2,5-Dimethyl-2,5-Di(Tert-Butylperoxy)hexyne-3 in solvent to Daphnia magna (water flea) was tested under static conditions for 48 hours in accordance with OECD guideline 202 and EU method C.2 (Akzo Nobel 2001).

The test item in solvent is immiscible with water and therefore a WAF was prepared. During chemical analyses, which were performed after finishing the test, the test substance could not be detected in WAF samples from the beginning and the end of the test. Therefore the test was repeated using an adjusted analytical method. The following dilutions of the WAF were tested during the second test: 1:32 -1:16 - 1:8 - 1:4 - 1:2 and the undiluted WAF. Chemical analyses of the control and WAF showed that the test substance is probably unstable under test conditions. At the beginning of the test a concentration of 5.31 mg/L was measured. At the end of the test a concentration of 0.38 mg/L was measured. The concentration at the beginning of the test was used for the calculation of the effect concentrations.

Sublethal effects, such as floating at the surface were observed in all dilutions. The number of animals floating on the surface seems to be related to the concentration of the test substance. In spite of these sublethal effects no test substance related immobility was observed in the undiluted WAF (5.31 mg/L; average initial concentration) or in any of the dilutions.

Acute toxicity to algae:

The algal toxicity of 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3 was determined in an algal growth inhibition test in accordance with the OECD guideline 201 (Akzo Nobel 2004).

The test substance is not miscible with water and therefore a 48 hours water accommodated fraction (WAF) was prepared. The green algae Pseudokirchneriella subcapitata was exposed to the following fractions of the WAF: 1:32, 1:16, 1:8, 1:4, 1:2 and the undiluted WAF of the test item in white mineral oil.

The chemical analyses performed demonstrated a concentration of parent compound in the water accommodated fraction of 3.76 mg/L at the beginning of the test and of < 0.3 mg/L after 24 hours of testing (half-life < 3.4 hours). This means that due to the followed approach of 48 hours of WAF preparation time, high concentrations of degradation products were present in the WAF and that it is likely that the effects are not caused by the parent compound but by the degradation products. Despite the instability of the parent compound, the effects are all calculated based on the concentration of parent compound as measured at the beginning of the test.

The toxicity of the test substance to exponentially growing culture of Pseudokirchneriella subcapitata was determined over an exposure period of 72 hours. The EbC50 (0-72 h) value of the test substance as calculated by extrapolation of the doses effect curve for P. subcapitata is 6.17 mg/L. The NOEC determined from the results is 1.88 mg/L, the LOEC is 3.76 mg/L.

Toxicity to microorganisms:

An activated sludge respiration inhibition test with the test item was performed according to OECD guideline 209 (United initiators 2015). The purpose of the 3-hour test was to evaluate the influence of the test item DYBP-85-WO on the activity of the activated sludge by measuring the respiration rate under defined conditions. The respiration rates (total, heterotrophic and nitrification oxygen uptake rates) of samples of activated sludge fed with synthetic sewage were measured in an enclosed cell containing an oxygen electrode after a contact time of 3 hours. Based on the preliminary information about the test item caused effect on the activated sludge inoculum, the test item DYBP-85-WO was investigated at the concentration of 1000 mg/L as a limit concentration, only. Defined amounts (in a form of the corresponding volumes) of the test item were added directly into the test vessels.

The observed oxygen consumption rates consequently the specific respiration rates were in the range of the blank controls, no inhibitory effect of the test item was observed. Under the conditions of the performed Activated Sludge Respiration Inhibition Test, the EC10 and EC50 values of test item was determined as higher than 1000 mg/L. Based on the statistical evaluation in this test the NOEC was ≥ 1000 mg/L.