branched-nonyl 3,5,5 trimethylhexanoate

Sediment toxicity

Additional information

No experimental data evaluating the toxicity to sediment organisms is available for isononyl isononanoate. Since the substance is readily biodegradable, chronic exposure of sediment organisms is unlikely. Furthermore, the substance is not toxic to aquatic organisms up to the limit of water solubility. In addition, available data indicate, that isononyl isononanoate is not bioaccumulative. Based on the available information, toxicity to sediment organisms is not expected to be of concern.

 

Intrinsic properties and fate

Isononyl isononanoate is readily biodegradable (91% CO2 evolution in 28 days; Barthel, 2011). 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, 2012a). Therefore, after passing through conventional STPs, only low concentrations of the substance is likely to be (if at all) released into the environment. Furthermore, the substance exhibits a log Koc value of > 5 and has low water solubility (< 0.05 mg/L). The Guidance on information requirements and chemical safety assessment, Chapter R7.b (ECHA, 2012a) states that once insoluble chemicals enter a standard STP, they will be extensively removed in the primary settling tank and fat trap and thus, only limited amounts will get in contact with activated sludge organisms. Nevertheless, once this contact takes place, these substances are expected to be removed from the water column to a significant degree by adsorption to sewage sludge (Guidance on information requirements and chemical safety assessment, Chapter R.7a, (ECHA, 2012b)) and the rest will be extensively biodegraded (due to ready biodegradability). Thus, discharged concentrations of these substances into the aqueous/sediment compartment are likely to be negligible. Considering this one can assume that the availability of isononyl isononanoate in the sediment environment is generally very low, which reduces the probability of chronic exposure of sediment organisms in general.

 

Aquatic ecotoxicity data

Acute and chronic aquatic toxicity tests of the substance to fish, invertebrates and microorganisms showed no adverse effects occurred in the range of the water solubility of the substance (< 0.05 mg/L). The obtained results indicate that isononyl isononanoate is likely to show no toxicity to sediment organisms as well.

 

Bioaccumulation

QSAR estimations using BCFBAF v3.01 resulted in BCF values of 113.1 - 484.3 L/kg using the Arnot-Gobas model which includes biotransformation (Müller, 2012). Exclusion of biotransformation resulted in clearly higher BCF values of 3937 - 13060 L/kg. Thus, it can be concluded that the substance will be extensively metabolized (half-life of 1.26 - 2.39 d) which reduces the bioaccumulation potential significantly. Therefore, isononyl isononanoate has a low potential for bioaccumulation and the highest calculated BCF of 484.3 L/kg is clearly below the trigger value of 2000 L/kg to be classified as bioaccumulative (B-criterion;ECHA Guidance R.11, 2012).

 

Conclusion

Since the substance is readily biodegradable, extensive degradation of this substance 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 the high log Kow, low water solubility and high adsorption potential, isononyl isononanoate will be bioavailable to sediment organisms mainly via feed and contact with suspended organic particles. The QSAR values for BCF estimated with the BCFBAF v3.01 program, Arnot-Gobas model including biotransformation, indicate that this substance has a low potential for bioaccumulation. Furthermore, aquatic toxicity data show that no effects occur up to the limit of water solubility. Therefore, isononyl isononanoate is unlikely to pose a risk for sediment organisms in general and testing is thus omitted.

 

References

ECHA (2012a): Guidance on information requirements and chemical safety assessment – Chapter 7b: Endpoint specific guidance. European Chemicals Agency, Helsinki.

 

ECHA (2012b): Guidance on information requirements and chemical safety assessment – Chapter 7a: Endpoint specific guidance. European Chemicals Agency, Helsinki.