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Toxicity to terrestrial arthropods

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Endpoint:
toxicity to terrestrial arthropods: long-term
Data waiving:
exposure considerations
Justification for data waiving:
other:

Description of key information

No data available. Considering all related information available, Bis(2-(2-butoxyethoxy)ethyl) adipate (CAS 141-17-3) is unlikely to pose a risk to terrestrial organisms.

Key value for chemical safety assessment

Additional information

No experimental data evaluating the terrestrial toxicity is available for Bis(2-(2-butoxyethoxy)ethyl) adipate (CAS 141-17-3).

Intrinsic properties and fate/ exposure

Bis(2-(2-butoxyethoxy)ethyl) adipate (CAS 141-17-3) 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, 2017a). Therefore, indirect exposure of the terrestrial environment via application of activated sludge to soil is very unlikely.

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 soil derived by equilibrium partitioning method (EPM) did not indicate a risk. The RCR is well below 1 for the terrestrial compartment and a risk to terrestrial species can thus be excluded. This approach is in line with the ECHA Guidance Document R.7c. Bis(2-(2-butoxyethoxy)ethyl) adipate (CAS 141-17-3) is considered to be in Soil Hazard Category 1 since high adsorption as well as persistence and high toxicity can be excluded. In this case a screening assessment using a PNEC soil derived by EPM is sufficient to omit additional experimental testing for soil organisms if it can be confirmed that the PEC/PNEC ratio is < 1.

Toxicity to aquatic/terrestrial microorganisms

The Guidance Document (ECHA, 2017) states that a test on soil microbial activity will only be additionally necessary for a valid PNEC derivation if inhibition of sewage sludge microbial activity has occurred. Since the substance reached 82% degradation in a ready biodegradation test, it can be assumed that it is not inhibitory to activated sludge microorganisms.

Metabolisms/Bioaccumulation

After absorption, Bis(2-(2-butoxyethoxy)ethyl) adipate is expected to be enzymatically hydrolysed in vivo by the ubiquitary enzyme carboxylesterase, yielding the corresponding alcohols and acid. QSAR estimations using BCFBAF v3.0 support the expected rapid biotransformation of this substance with BCF and BAF value of 6.33 L/kg (Arnot-Gobas, including biotransformation, upper trophic). The metabolism of the hydrolysis products (alcohol and carboxylic acid) is well established and not of concern in terms of bioaccumulation (for further information see Chapter 7.1 of the technical dossier). Literature data is also available on the metabolism of structurally related substances in soil microorganisms. This is supported by further evidence from literature data. This data showed that soil microorganism communities are well capable of degrading fatty acid esters (Hita et al., 1996 and Cecutti et al., 2002) and use them as energy source (Banchio & Gramajo, 1997). Hita et al. investigated the degradation of the model molecule Tristearin which is a Triglyceride containing of Glycerin tri-esterified with stearic acid in three different soils for 4 weeks. The amount of stearic acid increased in considerable amounts during the experiment showing the hydrolytic activity of lipases breaking the ester bonds. The investigation of ester fractions moreover showed the generation of new alkanoic acids (methyl stearate, ethyl stearate and propyl stearate) which were not determined in the controls. Nevertheless the amounts were no longer present after 4 weeks, which leads to the assumption that degradation by soil microorganisms had occurred. The same was shown by Cecutti et al. One soil sample was chosen and incubated with Methyl oleate (plant oil) for 120 d. Methyl oleate and its metabolites were completely degraded after 60 d. Streptomyces coelicolor, a common gram-positive soil bacterium uses fatty acids (C4-C18) as sole carbon end energy source indicating that fatty acids are not-toxic and can be used for catabolism (Banchio and Gramajo, 1997). The available literature data shows that soil microorganisms are capable to break-up ester bonds and degrade fatty acids in significant amounts. Moreover, the data indicated the non-toxic properties of fatty acids since they can be used as energy source.

Conclusion

Bis(2-(2-butoxyethoxy)ethyl) adipate is unlikely to pose a risk for terrestrial organisms based on a) unlikely exposure due to ready biodegradation and b) metabolism via common pathways, leading to expected low bioaccumulation potential and low toxicity. Taking all the available information, effects on soil organisms are thus not expected to be of concern, and consequently, no further testing is necessary.

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

No experimental data evaluating the terrestrial toxicity is available for Bis(2-(2-butoxyethoxy)ethyl) adipate (CAS 141-17-3).

Intrinsic properties and fate/ exposure

Bis(2-(2-butoxyethoxy)ethyl) adipate (CAS 141-17-3) 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, 2017a). Therefore, indirect exposure of the terrestrial environment via application of activated sludge to soil is very unlikely.

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 soil derived by equilibrium partitioning method (EPM) did not indicate a risk. The RCR is well below 1 for the terrestrial compartment and a risk to terrestrial species can thus be excluded. This approach is in line with the ECHA Guidance Document R.7c. Bis(2-(2-butoxyethoxy)ethyl) adipate (CAS 141-17-3) is considered to be in Soil Hazard Category 1 since high adsorption as well as persistence and high toxicity can be excluded. In this case a screening assessment using a PNEC soil derived by EPM is sufficient to omit additional experimental testing for soil organisms if it can be confirmed that the PEC/PNEC ratio is < 1.

Toxicity to aquatic/terrestrial microorganisms

The Guidance Document (ECHA, 2017) states that a test on soil microbial activity will only be additionally necessary for a valid PNEC derivation if inhibition of sewage sludge microbial activity has occurred. Since the substance reached 82% degradation in a ready biodegradation test, it can be assumed that it is not inhibitory to activated sludge microorganisms.

Metabolisms/Bioaccumulation

After absorption, Bis(2-(2-butoxyethoxy)ethyl) adipate is expected to be enzymatically hydrolysed in vivo by the ubiquitary enzyme carboxylesterase, yielding the corresponding alcohols and acid. QSAR estimations using BCFBAF v3.0 support the expected rapid biotransformation of this substance with BCF and BAF value of 6.33 L/kg (Arnot-Gobas, including biotransformation, upper trophic). The metabolism of the hydrolysis products (alcohol and carboxylic acid) is well established and not of concern in terms of bioaccumulation (for further information see Chapter 7.1 of the technical dossier). Literature data is also available on the metabolism of structurally related substances in soil microorganisms. This is supported by further evidence from literature data. This data showed that soil microorganism communities are well capable of degrading fatty acid esters (Hita et al., 1996 and Cecutti et al., 2002) and use them as energy source (Banchio & Gramajo, 1997). Hita et al. investigated the degradation of the model molecule Tristearin which is a Triglyceride containing of Glycerin tri-esterified with stearic acid in three different soils for 4 weeks. The amount of stearic acid increased in considerable amounts during the experiment showing the hydrolytic activity of lipases breaking the ester bonds. The investigation of ester fractions moreover showed the generation of new alkanoic acids (methyl stearate, ethyl stearate and propyl stearate) which were not determined in the controls. Nevertheless the amounts were no longer present after 4 weeks, which leads to the assumption that degradation by soil microorganisms had occurred. The same was shown by Cecutti et al. One soil sample was chosen and incubated with Methyl oleate (plant oil) for 120 d. Methyl oleate and its metabolites were completely degraded after 60 d. Streptomyces coelicolor, a common gram-positive soil bacterium uses fatty acids (C4-C18) as sole carbon end energy source indicating that fatty acids are not-toxic and can be used for catabolism (Banchio and Gramajo, 1997). The available literature data shows that soil microorganisms are capable to break-up ester bonds and degrade fatty acids in significant amounts. Moreover, the data indicated the non-toxic properties of fatty acids since they can be used as energy source.

Conclusion

Bis(2-(2-butoxyethoxy)ethyl) adipate is unlikely to pose a risk for terrestrial organisms based on a) unlikely exposure due to ready biodegradation and b) metabolism via common pathways, leading to expected low bioaccumulation potential and low toxicity. Taking all the available information, effects on soil organisms are thus not expected to be of concern, and consequently, no further testing is necessary.

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