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PBT assessment

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PBT assessment: overall result

Reference
Name:
Reaction mass of 7,7,9-trimethyl-4,13-dioxo-3,14-dioxa-5,12-diazahexadecane-1,16-diylbismethacrylate and 7,9,9-trimethyl-4,13-dioxo-3,14-dioxa-5,12-diazahexadecane-1,16-diylbismethacrylate
Type of composition:
boundary composition of the substance
State / form:
liquid
Reference substance:
Reaction mass of 7,7,9-trimethyl-4,13-dioxo-3,14-dioxa-5,12-diazahexadecane-1,16-diylbismethacrylate and 7,9,9-trimethyl-4,13-dioxo-3,14-dioxa-5,12-diazahexadecane-1,16-diylbismethacrylate
Reference substance:
Reaction mass of 7,7,9-trimethyl-4,13-dioxo-3,14-dioxa-5,12-diazahexadecane-1,16-diylbismethacrylate and 7,9,9-trimethyl-4,13-dioxo-3,14-dioxa-5,12-diazahexadecane-1,16-diylbismethacrylate
PBT status:
the substance is not PBT / vPvB
Justification:

The criteria given in the “Guidance on information requirements and chemical safety assessment, chapter R.11: PBT Assessment” (ECHA, 2017) are used as information to decide whether the substance may potentially fulfil the PBT or vPvB criteria.

 

Persistence Assessment

Based on the available data, the substance is not readily biodegradable (22% after 28d). Thus, the substance has to be considered as potentially P/vP.

 

Bioaccumulation Assessment

In accordance with ECHA Guidance R.11 (ECHA, 2017) Reaction mass of 7,7,9-trimethyl-4,13-dioxo-3,14-dioxa-5,12-diazahexadecane-1,16-diylbismethacrylate and 7,9,9-trimethyl-4,13-dioxo-3,14-dioxa-5,12-diazahexadecane-1,16-diylbismethacrylate is not considered to meet the screening criterion for bioaccumulation in aquatic species since the log Kow of 3.39 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 (15.75, calculated for both constituents by KOAWIN v.1.1) in combination with the log Kow > 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 a high absorption potential of the substance from the GI tract and low dermal absorption or absorption via inhalation. However, there is evidence for biotransformation and active transport of the substance after uptake. The substance is expected to undergo enzymatic hydrolysis in the GI tract prior to absorption resulting into smaller and altered hydrolysis products which are likely to be absorbed or excreted easier than the parent substance. 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. Two dermal metabolites and 20 hepatic metabolites were predicted for each of the main constituents of the substance using the QSAR OECD toolbox (v3.3.0.152, 2014). The metabolites are mainly the result of hydrolysis of the ester bonds and of a hydroxyl group being added to, or substituted with, a methyl group as well as the hydrolysis of the amino bond. The hydroxyl groups make the substances more water-soluble, more susceptible to metabolism and excretion via the urine. Furthermore up to 98 metabolites were predicted as a result of microbiological metabolic pathways (QSAR OECD toolbox, v3.3.0.152, 2014). For further details on the toxicokinetic behavior please refer to the toxicokinetic statement in IUCLID section 7.1.

Reliable QSAR models (BCFBAF Program v3.01) incorporated in the EPI Suite v4.1 interphase, were additional used to calculate the bioconcentration factors (BCF) of the substance. A BCF value of 80.1 L/Kg was predicted by the regression based model (Meylan, 1997) while a BCF of 6.47 L/Kg was estimated by the Arnot and Gobas model (2003) taking biotransformation into account (biotransformation rate kM = 50/d). These results show a low bioaccumulation potential of the substance and support the toxicocinetics outcome concerning a high rate of biotransformation after uptake.    

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 Assessment

A long-term toxicity result for Desmodesmus subspicatus is available with an ErC10 (72 h) of 0.21 mg/L (mean measured), which lays over the default value of 0.01 mg/L. Moreover, the test substance is not classified for toxicity according to the criteria in Annex XIII of Regulation (EC) No 1907/2006 based on Regulation (EC) No 1272/2008. Thus, the criteria set out in Annex XIII of Regulation (EC) No 1907/2006 are not met and the test substance is not considered to meet the T criterion.

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