Bis(2,6-diisopropylphenyl)carbodiimide

Endpoint summary

Description of key information

Key,Short-term toxicity to fish: LC₅₀(96h) > 0.064 mg/L (mean measured concentration) for Oncorhynchus mykiss based on mortality (semi-static, OECD 203, GLP)

Key, Short-term toxicity to aquatic invertebrates: EC₅₀(48h) = 0.00 40 mg/L (time-weighted mean measured) for Daphnia magna based on mobility (static, OECD 203, GLP)

Supporting, Short-term toxicity to aquatic invertebrates: EC₅₀(48h) > 1 mg/L (nominal) for Daphnia magna based on mobility (semi-static, OECD 203, GLP)

Supporting, Short-term toxicity to aquatic invertebrates: EC₅₀(48h) > 1000 mg/L (nominal) for Daphnia magna based on mobility (static, OECD 203, non-GLP)

Key, Long-term toxicity to aquatic invertebrates: NOEC (21d) = 5.43 mg/L (time-weighted mean measured) for Daphnia magna based on mortality, reproduction per introduced adult and reproduction per surviving adult (semi-static, OECD 211, GLP)

Key, Toxicity to aquatic algae and cyanobacteria: ErC₅₀(72h) > 0.0085 mg/L (geometric mean measured) for Desmodesmus subspicatus (static, OECD 201, GLP)

Additional information

Due to the very poor solubility of the registered substance in water (< 0.53 µg/L) and the fast hydrolysis (DT₅₀ = 153.62 h at 25 °C) no standard application could be used for the preparation of test solution for aquatic toxicity testing. As recommended in the OECD Guidance Document No. 23 on aqueous phase aquatic toxicity testing of difficult test chemicals (second edition, February 2019) solubility pre-experiments were performed before initiation of any aquatic toxicity testing to determine the maximum dissolved concentration that can be achieved in the specific test solution under test conditions. The results of the solubility experiment were used to form a basis of, and justification for, the test solution preparation procedures adopted for the toxicity tests and a reference point (i.e. saturation concentration in test solution under test conditions) against which the test results can be evaluated. As test solutions (containing undissolved organic matter, salts, etc.) are much more complex than distilled water, the maximum achievable dissolved concentration of the test substance in the test solution, i.e. saturation concentration, is not the same as the water solubility of the test chemical.

 

Short-term toxicity to fish

The acute toxicity of the registered substance to fish was tested according to OECD Guideline 203 in a semi-static freshwater test with Oncorhynchus mykiss (Wetton and Mullee, 2002). Based on a range-finding study, a "limit test" was conducted at a concentration of 0.10 mg/L. The test solution was prepared using a preliminary solution in dimethylformamide. No mortality or any sublethal effects were observed following exposure for 96 h. Therefore, the 96 hours LC₅₀ was determined to be greater than nominal 0.10 mg/L and the 96 hours No Observed Effect Concentration (NOEC) was at least nominal 0.10 mg/L, corresponding to a mean measured concentration of 0.064 mg/L, respectively. This was the highest obtainable test concentration due to the limited solubility of the test material in water and auxiliary solvent, and having due regard for the amount of auxiliary solvent permitted in the test under OECD guidelines.

 

Short-term toxicity to aquatic invertebrates

Regarding acute toxicity to aquatic invertebrates of the registered substance three experimental results are available, each conducted according to OECD Guideline 202 with Daphnia magna as test organisms.

The key study by Wetton and Mullee (2002) was conducted using a static test design. Based on the range-finding study, the definitive test was conducted with test concentrations of nominal 0.0010, 0.0018, 0.0032, 0.0056, 0.010, 0.018, 0.032, 0.056 and 0.10 mg/L (each in 100 µL DMF/L), a solvent control (100 µL DMF/L) and a control, corresponding to time-weighted mean measured test concentrations of 0.000490, 0.000766, 0.00171, 0.00326, 0.00628, 0.00966, 0.0208, 0.0328 and 0.0597 mg/L.

The test solution was prepared using a preliminary solution in dimethylformamide. Based on the obtained results, the 48 h EC₅₀value was determined to be nominal 0.0067 mg/L with 95 % Confidence limits of 0.0057 - 0.0079 mg/L, corresponding to 0.0040 mg/L with 95 % Confidence intervals of 0.0033 - 0.0047 mg/L based on time weighted mean measured concentrations. The corresponding 48 h No Observed Effect Concentration (NOEC) is nominal 0.0032 mg/L, corresponding to 0.0017 mg/L based on time weighted mean measured concentrations. The nominal concentration of 0.10 mg/L was the highest obtainable test concentration due to the limited solubility of the test material in water and auxiliary solvent, and having due regard for the amount of auxiliary solvent permitted in the test under OECD guidelines.

A semi-static test was conducted in the supporting study by Weyers (2009) with a final test concentration of nominal 1 mg/L, representing the limit of solubility in the used test medium following direct weighing, prolonged stirring and subsequent filtration.

No toxic effects against Daphnia were observed at the nominal limit test concentration of 1 mg/L which after aseptic filtration resulted in effective concentrations of < 0.275 μg/L (the limit of detection). Accordingly, the 48 h EC₅₀was determined to be nominal > 1 mg/L, corresponding to < 0.275 µg/L effective concentration. Thus, no toxic effects were observed under the established test conditions.

The second supporting study was performed using Water Accommodated Fractions (WAF) with a concentration of nominal 1000 mg/L (Rudolf, 2004). Since no effects were observed, the 48 h EC₅₀was found to be greater than the tested concentration of nominal 1000 mg/L.

 

Long-term toxicity to aquatic invertebrates

For the determination of the long-term toxicity to aquatic invertebrates female Daphnia (3.5 to 5.5 hours old) were exposed in a semi-static test to aqueous test media containing the test item at concentrations of 0.206, 0.65, 2.05, 6.44 and 20.3 µg test item/L (each in 100 µL DMF/L) ), a solvent control (100 µL DMF/L) and a control, corresponding to time weighted average concentrations of 0.170, 0.526, 1.68, 5.43 and 19.9 µg test item/L, for a period of 21 days under defined conditions. Based on the obtained results the 21 d NOEC for the parameters mortality of adults, the number of offspring per introduced adult and the number of offspring per surviving adult was determined to be 5.43 µg/L based on the time-weighted mean measured concentrations of the test item in the test medium.

 

Toxicity to aquatic algae and cyanobacteria

Desmodesmus subspicatus was used to investigate the short-term toxicity of the registered substance according to OECD Guideline 201 (Weyers, 2009). Because of the low solubility of the test item, a limit test was performed at the limit of water solubility under test conditions in order to demonstrate that the EC50 values (based on yield as well as on growth rate) are greater than this concentration. After two range-finding studies, the final test concentration was chosen as 1 mg/L. Analysis of the yield and growth rate of the algal population gave the following results expressed in terms of geometric mean measured concentrations: ErC50(72h) > 0.0085 mg/L and EyC50(72 h) > 0.0085 mg/L, as well as NOEC(r) >= 0.0085 mg/L and NOEC(y) >= 0.0085 mg/L. Nominal value is given as 1 mg/L for all effect parameters.

 

Toxicity to microorganisms

The acute toxicity of the registered substance to microorganisms was tested in two experiments according to OECD Guideline 209 (Neuhahn, 2008 and Kanne, 1988). In both studies, activated sludge was used as inoculum and the incubation time was 3h. 3,5-Dichlorophenol was used as reference compound. In the first test (key study) the EC50 was determined to be greater than 1000 mg/L and in the supporting data, an EC50 greater or equal to 10,000 mg/L was reported.

 

Considering all available data on short- and long-term toxicity to aquatic organisms, no acute or chronic toxicity is recorded for all three trophic levels at the limit of solubility in the respective aquatic test media or at levels up to the water solubility of < 0.53 µg/L (Holzaht-Grimme, 2019). Hence, there is scientific evidence, that the registered substance does not need to be classified as harmful to the aquatic environment according to Regulation (EC) No 1272/2008 and “No hazard” is concluded for the freshwater compartment in accordance with ECHA Guidance R.7b (June 2017). No further considerations are required.