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Sediment toxicity

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Description of key information

In accordance with column 2 of Annex X to Regulation (EC) No 1907/2006 (REACH) a study on toxicity to sediment organisms is considered scientifically not necessary. Therefore, this endpoint was waived.

Key value for chemical safety assessment

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Non-submission justification

According to column 2 of Annex X to Regulation (EC) No 1907/2006 (REACH) long-term toxicity testing shall be proposed by the registrant if the results of the chemical safety assessment indicate the need to investigate further the effects of the substance. According to theGuidance Document on Sediment Toxicity Tests and Bioassays for Freshwater and Marine Environments (SETAC 1993, c.f. ECHA Guidance on Information Requirements and Chemical Safety Assessment, Chapter R.7b, Version 4.0, June 2017)substances with a Koc<500 – 1000 l/kg are in general not likely sorbed to sediment. Thus, a log Kocor log Kowof ≥3 is considered as trigger value for sediment effects assessment.

 

The experimental log Pow of isobutyl acrylate was determined to be 2.38 (please refer to IUCLID section 4.7) indicating that adsorption is very unlikely. Moreover, the substance was assessed to be readily biodegradable which implies that it decompose rapidly in the environment (please see IUCLID section 5.2.1). However, using QSAR the log Koc of isobutyl acrylate was predicted to be 1.53 (Koc = 33.8). Hence, in compliance with above mentioned guidance documents, the Koc and log Koc for isobutyl acrylate are clearly below the trigger values for sediment effect assessment.

 

Further, isobutyl acrylate has a low potential for bioaccumulation. The measured log Kow of 2.38 (25 °C) and the calculated BCF of 17.3 give no indication for a potential for bioaccumulation (please refer to IUCLID section 5.3.1). Consequently, based on available information and its intrinsic properties isobutyl acrylate is not considered PBT / vPvB (please see IUCLID section 2.3). Additionally, environmental exposure is deemed negligible. The use of isobutyl acrylate as a monomer, almost exclusively in closed systems for the production of polymers, indicates that environmental exposure would be limited. The volatility of isobutyl acrylate provides for volatilization of any releases to the air. Distribution modeling (see IUCLID section 5.4.3) demonstrated that about 95.78% of the substance hypothetically released to the environment will be distributed to the air, 4.06% to the water phase, approximately 0.08% to the soil and only 0.08% to the sediment compartment. Isobutyl acrylate is slowly photodegradable but readily biodegradable; accidental releases to the environment would not result in accumulation or persistence in the sediment.

 

Finally, the Chemical Safety Assessment according to Article 14 and Annex I of Regulation (EC) No 1907/2006 (REACH) did not indicate any need for further assessment of toxicity to sediment organisms. 

 

Therefore, a long-term toxicity study in sediment organisms is considered scientifically not necessary. The PNEC sediment was thus estimated based on the equilibrium partitioning method.

 

 

Reference

SETAC (1993): Guidance Document on Sediment Toxicity Tests and Bioassays for Freshwater and Marine Environments. From the Workshop on Sediment Toxicity Assessment at Renesse, Netherlands on 8-10 November 1993. Hill I, Mathiessen P, Heimbach F (Eds). Society of Envionmental Toxicology and Chemistry – Europe, Brussels.