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PBT assessment

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PBT assessment: overall result

Reference
Name:
2,4,6-triisopropyl-m-phenylene diisocyanate
Type of composition:
legal entity composition of the substance
State / form:
liquid
Reference substance:
Composition 1
PBT status:
the substance is not PBT / vPvB
Justification:

2,4,6-triisopropyl-m-phenylene diisocyanate (TRIDI)

The available information regarding persistence, bioaccumulation and toxicity properties of the registered substance is sufficient and summarized as follows:

The test substance hydrolyses rapidly in fresh water. The abiotic degradation was > 90% within 3 min at 20 °C. Main transformation product is 2,4,6 -triisopropyl-m-phenylene diamine (TRIDA) and polymeric ureas were determined as potential minor hydrolysis products. The test substance is therefore considered not P/not vP.

The BCF of TRIDI has been evaluated with a WoE approach using QSAR. A BCF of 152.8 L/kg wet-wt.-  232.2 L/kf wet-wt have been calculated, indicating a low potential for bioaccumulation. As the substances hydrolyses rapidly with T1/2 = 37 seconds (abiotic degradation > 90% within 3 min) attention must be paid to the main transformation product TRIDA. Based on the available information on calculated BCF value and the hydrolysis result, the test substance is expected to not bioaccumulate at a significant rate.

The substance is classified as Carc. 2, H351: Suspected of causing cancer and therefore fulfills the requirements to be considered as T for the PBT assessment.

Accordingly, the test substance does not fulfill the relevant criteria for a PBT substance and is also not considered as a vPvB-substance.

Due to the fast hydrolysis and the resulting instability of the test material, the main transformation products are considered and assessed separately.

The test material is hydrolytically unstable and undergoes rapid hydrolysis. A recent study showed that for the test material abiotic degradation > 90% was observed within 3 min at 20 °C in demineralized water with a half life time of about 37 seconds (Neuland, 2020). Accordingly, 1,3,5-triisopropyl-2,4-diaminobenzene (TRIDA, CAS 6318-09-8) can certainly be assessed as most predominant hydrolysis product, beside polymeric or oligomeric ureas as potential minor hydrolysis products.

Polymeric ureas are polymers that result from the polyaddition of isocyanates and amines. The product of hydrolysis of the isocyanate group is an amine, which itself reacts with another isocyanate group to yield an urea (e.g. Gilbert, 1988; Yakabe et al 1999; Bailey et al. 2003; ECHA, 2012).

Polymeric ureas:

The available information regarding persistence, bioaccumulation and toxicity properties of polymeric ureas is sufficient and summarized as follows.

Because polymeric ureas are inert and insoluble with a high molecular weight it can be concluded, that polymeric ureas are very persistent, but neither bioaccumulative nor toxic and consequently do not meet the PBT-criteria.

Regardless of the evaluation of the available data, polymeric ureas are considered as polymers under REACH. Therefore they do not have to be registered and evaluated according to Chapter 1; Article 2, Paragraph 9 Regulation No. 1907/2006.

2,4,6 -triisopropyl-m-phenylene diamine (TRIDA)

The available information regarding persistence, bioaccumulation and toxicity properties of the main hydrolysis product TRIDA is sufficient and summarized as follows:

Little data on the biodegradability of the test substance is available. The substance is classified as Aquatic Chronic 3, H412: "Harmful to aquatic life with long lasting effects" in the disseminated dossier at ECHA website. It can be assumed that TRIDA is not readily biodegradable.

The LogKow indicated a low potential to bioaccumulate. Further evidence will be provided when the OECD 305 study is finalised.

Long-term toxicity tests with the test substance are available. Due to the rapid hydrolysis into TRIDA, results can also be used to assess the ecotoxicity of TRIDA. Currently a long-term toxicity study to fish is ongoing, but based on the results of a chronic toxicity study to daphnia and a toxicity study to algae, no chronic hazard was determined for the aquatic environment. Furthermore the substance is not classified into the respective hazard categories for human health according to the disseminated dossier of TRIDA at ECHA website.

Accordingly, the test substance does not fulfill the relevant criteria for a PBT substance and is also not considered as a vPvB-substance.