3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate

Biodegradation in water and sediment: simulation tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: sediment simulation testing

Data waiving:

exposure considerations

Justification for data waiving:

the study does not need to be conducted because direct and indirect exposure of sediment is unlikely

other:

Transformation products:

not specified

Reference 2

Endpoint:

biodegradation in water: simulation testing on ultimate degradation in surface water

Data waiving:

exposure considerations

Justification for data waiving:

other:

Transformation products:

not specified

Description of key information

 The biodegradation testing in water and sediement has been judged to be not necessary in accordance with column 2 of REACH Annex IX and X 9.2 and also in accordance with section 3 of REACH Annex XI. 

Additional information

The biodegradation testing in water and sediement has been judged to be not necessary in accordance with column 2 of REACH Annex IX and X 9.2 and also in accordance with section 3 of REACH Annex XI. In accordance with column 2 of REACH Annex IX and X, further biotic degradation testing is not proposed because the results of the chemical safety assessment do not indicate any need to investigate further the biodegradability of the substance and its degradation products. The chemical safety assessment, conducted using the CHESAR-tool, demonstrates that for all uses, the environmental exposure levels estimates (PEC) do not exceed the appropriate PNEC values (PEC/PNEC < 1); precisely, all RCR are≤0.01 (marine water: RCR≤0.01 ). These results are reported in the chemical safety report that comprises all uses of the lifecycle and corresponding relevant compartments in exposure scenarios for the substance. In the CSR operational conditions (OC) and risk mitigating measures (RMM) define how direct or indirect exposure into the environment is prevented. Therefore, in accordance with section 3 of REACH Annex XI simulation testing is judged no more relevant.

Additionally, as no biodegradation (0%) was observed in a study on ready biodegradability it is not expected that significant degradation would occur in a simulation test. The test substance is considered as non-biodegradable in the surface water, sediment, and soil compartment. Moreover, biodegradation is irrelevant as primary degradation step because immediate hydrolysis takes place. The general water solubility of isophorone diisocyanate is relatively low, 15 mg/L (23°C) and when the substance comes in contact with water the diisocyanate groups of isophorone diisocyanate react by forming amines and CO2. The amines formed react further with unreacted diisocyanate groups of isophorone diisocyanate homopolymer resulting in oligo- and subsequently polyurea components. For the hydrolysis products it is known that 42 % of isophorone diamine degraded within a period of 31 days in a simulation study which is comparable to OECD guideline 303. In this study DOC removal from the water phase was analyzed indicative for the biodegradation of the substance.  The resulting polyurea molecules are considered persistent in the environment, however due to their high molecular weight they are also considered as insoluble in water, not bioavailable and non-toxic to organisms.