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Diss Factsheets

Ecotoxicological information

Endpoint summary

Administrative data

Description of key information

Additional information

The main conclusions in this chapter have been prepared in accordance with the draft SIDS initial assessment report OECD (2005).

The inherent property of 4,4’-methylenedicyclohexyl diisocyanate is to hydrolyse in an aquatic environment. The hydrolysis product is - beside insoluble oligomeric and polymeric ureas - the corresponding 4,4´-methylenedicyclohexyl diamine. As the half life of the parent substance was determined to be 2 h and as the test solutions were stirred for 24 h it can be assumed that only the hydrolysis products were present in the test solutions andand thus potential effects were caused by the hydrolysis products rather than bythe parent substance. In the following the toxicity of 4,4’-methylenedicyclohexyl diisocyanate and its hydrolysis products is reported. Tests were conducted according to the GLP requirements and specially laid down test conditions.

Before the actual start of each ecotoxicity study (Danio rerio (formerly Brachydanio rerio), Daphnia magna and Scenedesmus subspicatus) pre-treatments were performed with 4,4’-methylenedicyclohexyl diisocyanate according to the recommendation mentioned in the “OECD Guidance Document on aquatic toxicity testing of difficult substances and mixtures” in order to accelerate test substance solution. For that purpose the solutions of the test substance were prepared at a nominal concentration that was 5-fold higher than the maximum water solubility reported for 4,4’‑methylenedicyclohexyl diisocyanate in preliminary tests. The solutions were treated in water with ultra-turrax 60 s/8000 rpm, afterwards stirred for 24 hours on a magnetic stirrer and finally filtered. Because of the short half-life of 4,4’-methylenedicyclohexyl diisocyanate, testing with the degradation products is required and has been conducted as seen in this test. Filtration removed additional insoluble hydrolysis products. Substance concentrations (mainly the soluble hydrolysis product methylene bis(4-cyclohexyldiamine)) were determined as TOC and back-calculated to the parent compound.