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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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Description of key information

According to REACH Annex IX, 9.3.2, column 2 the bioaccumulation study does not need to be conducted if the substance has a low potential for bioaccumulation.  The registered substance exhibits a dissipation time in water less than the cut-off value of 12 h and is therefore considered as hydrolytically unstable. Hence, the hydrolysis products need to be evaluated with regard to bioaccumulation. The hydrolysis products are either characterised by a low potential for bioaccumulation (log Kow <3) or have a low potential to cross biological membranes. 

Key value for chemical safety assessment

Additional information

According to experience with the substance itself as well as with similar diisocyanates, the amines formed in the initial hydrolysis step, which is associated with elimination of carbon dioxide, have a high reactivity towards unreacted isocyanate. The consequence is that in the hydrolysis of isophorone diisocyanate predominantly polyurea molecules are formed. They are insoluble in water. Their formation was observed in the hydrolysis study of Infracor GmbH (2000) (see 5.1.2) who reported that droplets settled on the bottom of the test vessel and became increasingly coated with a white layer.

Due to their molecular size, low mobility and high log Kow the hydrolysis products are not bioavailable (low potential to cross biological membranes).