Registration Dossier

Environmental fate & pathways

Bioaccumulation: aquatic / sediment

Currently viewing:

Administrative data

Link to relevant study record(s)

Description of key information

A waiver is presented based on rapid hydrolysis and limited potential to be taken up by biota. As a summary, it is demonstrated

1. that performance of a BCF study is technically not possible due to rapid hydrolysis where parent components removed quickly

2. that hydrolysis products have indeed not been found in studies but that theoretical small ureas exceed by far the standard values for logKow and molecular diameter.

3. estimated values of a primary hydrolysis product show a low tendency for bioaccumulation (BCF 3.2)

Key value for chemical safety assessment

Additional information

The waiving is based on three arguments indicating that performance of a BCF study is scientifically not necessary and technically not possible::

1. As a consequence of the results of hydrolysis experiments (Allmendinger and Tretzel 2018), performance of a bioconcentration study with 3-Isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate, oligomers appears technically not feasible. In a flow-through test the test compound is kept in a reservoir which is typically renewed daily. Based on a half-life of about 2 hours the requirement of the test guideline OECD 305 for stable conditions throughout the whole study cannot be satisfied.

2. The substance has very limited potential to be taken up by biota. According to ECHA guidance document R11, this is "indicated by several factors based on substance properties listed below. These indicators should be confirmed by other information to exclude the possibility of a high bioaccumulation potential. If such a lack of significant uptake is proven, the substance can be considered as not B and not vB. In such a case, further evaluation of the B and vB criteria is not necessary. It should be noted that the only conclusion drawn based on this information is that the substance is not (very) bioaccumulative, and not that the substance can’t be taken up at all. A substance is unlikely to meet the B criterion (i.e. unlikely to have a BCF >2,000) if some or all of the following indicators are met:"

a) The smallest theoretic possible primary hydrolysis product an average maximum diameter (Dmax aver) of greater than 17 A. The smallest theoretic possible hydrolysis product has maximum diameter of about 22 A (QSAR). Although a different model as OASIS was used (Marvin Scetch), the obtained value is far away from the given standard value.

b) octanol-water partition coefficient as Log Kow >10: The calculated value of the simplest molecule with an IPDI allophanate structure with a reliable model (Episuite) is 10.4. The urea as a theoretical primary hydrolysis product had a logKow of 15.4.

3. For the primary hydrolysis product of IPDI allophanate, NCO terminated a BCF of 3.2 was predicted using the Estimation Program Interface (EPI) Suite version 4.11.