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Sediment toxicity

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Description of key information

The chemical safety assessment according to Annex I of Regulation (EC) No. 1907/2006 does not indicate the need to investigate further the effects on sediment organisms. Based on the presented information, toxicity to sediment organisms is not expected to be of concern.

Key value for chemical safety assessment

Additional information

Since Bis(2-(2-butoxyethoxy)ethyl) adipate (CAS 141-17-3) is readily biodegradable, chronic exposure of sediment organisms is unlikely. In addition, the substance is not expected to bioaccumulate, due to rapid metabolism. Based on the available information, toxicity to sediment organisms is not expected to be of concern.

Distribution to the environmental compartments, intrinsic properties and fate

Since direct release of Bis(2-(2-butoxyethoxy)ethyl) adipate to the aquatic system is not anticipated, release to the aquatic compartment might occur via sewage treatment plants only. However, Bis(2-(2-butoxyethoxy)ethyl) adipate is readily biodegradable. According to the Guidance on information requirements and chemical safety assessment, Chapter R.7b, readily biodegradable substances can be expected to undergo rapid and ultimate degradation in most environments, including biological Sewage Treatment Plants (STPs) (ECHA, 2017). Therefore, after passing through conventional STPs, only low concentrations of these substances are likely to be (if at all) released into the environment. If the substance would be released into the aquatic environment, partitioning into the sediment is not likely based on its high water solubility and low adsorption potential. The substance would rather remain in the water phase, where rapid biodegradation will take place.

Ecotoxicity data

Even though the experimental data from three trophic levels indicate aquatic toxicity (lowest effect concentrations: LC50 (96 h) 13 mg/L for freshwater fish and ErC10 (72 h) of 13.3 mg/L for freshwater algae) sediment organisms are not expected to be at risk. The environmental exposure assessment using a PNEC sediment derived by equilibrium partitioning method (EPM) did not indicate a risk. The RCR is well below 1 for the sediment compartment and a risk to sediment species can thus be excluded.

Metabolisms/Bioaccumulation

The test substance has a log Kow of 3.24 (KOWWIN v1.67) indicating a low potential for bioaccumulation. Due to the rapid environmental biodegradation and metabolism via enzymatic hydrolysis, a relevant uptake and bioaccumulation in aquatic organisms is not expected. After absorption, Bis(2-(2-butoxyethoxy)ethyl) adipate is expected to be enzymatically hydrolyzed by carboxylesterases. Enzymatic breakdown will initially lead to the free fatty acid and the free alcohol. From literature it is well known, that these hydrolysis products will be metabolized and excreted in fish effectively (Heymann, 1980; Lech & Bend, 1980; Lech & Melancon, 1980; Murphy & Lutenske, 1990). This is supported by a low calculated BCF value of 6.33 L/kg ww (BCFBAF v3.01, Arnot-Gobas, including biotransformation, upper trophic). Please refer to Chapter 5.3 of the technical dossier for a detailed overview on bioaccumulation. Thus, taking all information into account, the bioaccumulation of Bis(2-(2-butoxyethoxy)ethyl) adipate is assumed to be low.

Conclusion

Due to its readily biodegradable nature, extensive degradation of Bis(2-(2-butoxyethoxy)ethyl) adipate in conventional STPs will take place and only low concentrations are expected to be released (if at all) into the environment. Once present in the aquatic compartment, further biodegradation will occur and, due to its high water solubility and low adsorption potential, the substance is not expected to partition into the sediment. However, in case of uptake by sediment species, extensive and fast biotransformation of the substance by carboxylesterases into fatty acids and the corresponding alcohol is expected. The supporting BCF/BAF values estimated with BCFBAF v3.01 (Arnot-Gobas, including biotransformation, upper trophic) also indicate that this substance will not be bioaccumulative (well below 2000 L/kg). Therefore, Bis(2-(2-butoxyethoxy)ethyl) adipate is unlikely to pose a risk for sediment organisms in general and testing is thus not required.

A detailed reference list is provided in the technical dossier (see IUCLID, section 13) and within CSR.

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