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Diss Factsheets

PBT status:
the substance is not PBT / vPvB
Justification:

The PBT assessment of Hexamethylene diisocyanate, trimers, reaction products with 2-hydroxyethyl acrylate (CAS 162492-01-5) is based on the criteria set out in the “Guidance on information requirements and chemical safety assessment, Chapter R.11: PBT Assessment” (ECHA, 2017).

 

 

Persistence

One OECD 301 screening study is available investigating the ready biodegradability of the substance. After 28 d the substance reached a degradation of 0%. Thus, the substance does not fulfill the criteria for ready biodegradability and is therefore considered to be potentially P/vP.

 

Bioaccumulation

In accordance with ECHA Guidance R.11 (ECHA, 2017) Hexamethylene diisocyanate, trimers, reaction products with 2-hydroxyethyl acrylate (CAS No. 162492-01-5) is not considered to meet the screening criterion for bioaccumulation in aquatic species since the log Kow of 4.23 is below the trigger value of 4.5. However, according to ECHA Guidance R.11 (ECHA, 2017) there is indication that accumulation in air breathing organisms might occur based on the calculated log Koa of > 5 (31.67 - 39.93) in combination with the log Pow > 2. These screening values (Kow and Koa) referred to in the ECHA Guidance R.11 are a function of the modelled organisms, food webs and environments used to obtain these values. To develop this partition coefficient combination it was clearly indicated in the guidance that biomagnification potential is only assumed for substances with high chemical absorption efficiency from the diet, no biotransformation after absorption and negligible active transport (in or out).
The evaluation of the toxicokinetic behavior indicates that due to the low water solubility (< 0.54 mg/L) and the high log Pow value (4.23) absorption might be limited by the inability to dissolve into gastrointestinal fluids(GI) fluids. However, enzymatic hydrolysis is expected and unlike the parent substance, the resulting hydrolysis products are likely to be absorbed. Even though the absorption of the hydrolysis products is higher compared to the parent substance, no toxic effects were recorded in the available toxicological studies (LD50 > 2000 mg/kg bw). Furthermore, dermal absorption and absorption via inhalation are assumed to be low. The substances absorbed from the GI tract will be transported via the portal vein to the liver, where further metabolism can take place. Substances that are absorbed through the pulmonary alveolar membrane or through the skin enter the systemic circulation directly before transport to the liver where metabolization will take place. These substances are not expected to accumulate in adipose tissue due to the lack of lipophilic groups.
Up to 57 metabolites were predicted to result from various microbiological metabolization pathways of test substance (QSAR OECD toolbox, v3.3.0.152, 2014).The results of the OECD Toolbox prediction substantiate the information on metabolism known from general literature (Lehninger, 1993). The hydrolysis products may be conjugated (e.g. glucuronidated) to form polar molecules suitable for excretion or metabolism. The hydrolysis products of hexamethylene diisocyanate, trimers, reaction products with 2-hydroxyethyl acrylate will be conjugated with e.g. glutathione to form more water-soluble molecules and excreted via the urine or metabolised. The formation of CO2 as metabolite is also predicted, which will be excreted via exhaled air. For further details on the toxicokinetic behavior please refer to the toxicokinetic statement in IUCLID section 7.1.
In conclusion, the trigger values for biomagnification in air-breathing (terrestrial) organisms as stipulated in the ECHA Guidance R.11 are likely to overestimate the potential for biomagnification in the food chain. Even though absorption via oral exposure cannot be excluded the described metabolic and excretion pathways are likely to minimize biomagnification in the food chain.

 

Toxicity

The available effect concentration for long-term toxicity to aquatic organisms is > 0.01 mg/L. Therefore, the substance does not meet the criteria set out in Annex XIII of Regulation (EC) No. 1907/2006 and it is concluded that the substance is not T.

 

In conclusion, the substance is not PBT/vPvB.