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Long-term toxicity to fish

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Reference
Endpoint:
fish early-life stage toxicity
Data waiving:
other justification
Justification for data waiving:
other:

Description of key information

No data on long-term toxicity on fish are available.

Key value for chemical safety assessment

Additional information

N,N''-(isobutylidene)diurea (CAS 6104-30-9) is characterized by a high water solubility (0.3 - 3 g/L at 20 °C), a low potential for adsorption (log Koc = 0.3616 - 1, KOCWIN v2.00), a low potential for bioaccumulation (Log Kow: -0.903 at 23 °C) and ready biodegradability.

Short-term toxicity studies for fish, aquatic invertebrates and algae are available for N,N''-(isobutylidene)diurea (CAS 6104-30-9) resulting in the following effect values: For fish a LC50 (96 hours) of > 1000 mg/L (nominal) was determined for Salmo gairdneri. Aquatic invertebrates showed an EC50 (48 hours) of 500 mg/L ( nominal) for Daphnia magna and an ErC50 (72hours) of > 500 mg/L (nominal) was reported for algae (Scenedesmus subspicatus). These results indicate that N,N''-(isobutylidene)diurea (CAS 6104-30-9) is not acutely toxic to aquatic organisms. Furthermore, no indication of more sensitivity for one trophic level is given based on the acute data.

No chronic tests on aquatic organisms are available. Due to the ready biodegradability of N,N''-(isobutylidene)diurea (CAS 6104-30-9), the test substance is estimated to be rapidly and ultimately degraded in sewage treatment plants. As mentioned in the Guidance on Information Requirements and Chemical Safety Assessment, Chapter R.7b (ECHA, 2017), the ready biodegradability of a substance can be an indication of rapid and ultimate degradation in most environments, including biological sewage treatment plants (STP). Due to the ready biodegradation, it is assumed that the discharged concentration of N,N''-(isobutylidene)diurea (CAS 6104-30-9) in the effluent of conventional STPs is negligible. Thus, insignificant release into the aqueous compartment is expected. Furthermore, the substance is expected to undergo rapid and ultimate degradation if released into the water compartment. Thus, persistence and hence long-term exposure of aquatic organisms is not expected due to the ready biodegradability of the substance. In addition, the low log Pow of -0.903 at 23 °C indicates a low potential for bioaccumulation. Therefore, as persistence and bioaccumulation could be excluded for N,N''-(isobutylidene)diurea (CAS 6104-30-9), no chronic aquatic toxicity is expected and thus, no chronic fish toxicity testing is needed.

 

In conclusion, based on following facts, no long-term testing with fish is needed:

- The substance is not acutely toxic to aquatic organisms.

- The substance show no indication of more sensitivity for one trophic level based on the acute data.

- No persistence based on ready biodegradability

- Low bioaccumulation potential

- No chronic aquatic toxicity is expected

- Avoidance of unnecessary vertebrate testing for animal welfare reasons