2,4,6-triisopropyl-m-phenylene diisocyanate

PBT assessment

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:

2,4,6-triisopropyl-m-phenylene diisocyanate

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. Accordingly, the bioaccumulative potential was analysed for the main hydrolysis product 2,4,6-triisopropyl-m-phenylene diamine (TRIDA, CAS 6318-09-08). The study was running under GLP according to OECD TG 305-I using aqueous exosure. Based on the mean measured concentration of the test material in the test water, the bioconcentration factor was determined for steady state (BCF_SS), including a normalisation to 5% lipid content (BCF_SSL) and was 1.44-1.88 L/kg and 4.5-6.1 L/kg, respectively, indicating a low potential for bioaccumulation. The test substance is therefore considered not B/not vB.

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 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. It can be assumed that TRIDA is not readily biodegradable. The substance is therefore considered P not vP.

The LogKow indicates a low potential to bioaccumulate. This indication is proven by the results of the bioaccumulation study performed with TRIDA as main hydrolysis product according to OECD TG 305-I indicating a low potential for bioaccumulation with a key value of 6.1 L/kg as a worst-case assumption. The test substance is therefore considered not B/not vB.

No chronic ecotoxicity data is available for the substance TRIDA besides an short-term toxicity test to fish published at the disseminated dossier at ECHA website. The test was performed according to ISO 7346-1. The LC50 (96h) was 56.2 mg/L. However, as the BCF of TRIDA was experimentally determined to be far below 500 the substance does not need to be classified.

As TRIDI hydrolyses rapidly to the main transformation product TRIDA, ecotoxicity tests on TRIDI can also be used for the assumption of ecotoxicity of TRIDA. The EC10 determined in the long-term toxicity tests with TRIDI were ≥ 0.01 mg/L for all three trophic levels. Accordingly, no long-term toxicity to the aquatic environment has to be considered for TRIDA.

Furthermore the substance is not classified into the respective hazard categories for human health according to the disseminated dossier of TRIDA at ECHA website. The test substance is therefore considered not T.

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