Isooctadecyl pivalate

Toxicity to soil macroorganisms except arthropods

Link to relevant study record(s)

Reference

Endpoint:

toxicity to soil macroorganisms except arthropods: long-term

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Description of key information

The Chemical Safety Assessment does not indicate the need to further investigate the toxicity to soil macroorganisms.

Additional information

No experimental data is available, in which the toxicity of Isooctadecyl pivalate (CAS 58958-60-4) to soil macroorganisms was assessed. However, the Chemical Safety Assessment does not indicate the need for further assessment of soil macroorganisms. According to Regulation (EC) No. 1907/2006, Annex X, Column 2, 9.4 there is no need for further studies on the effects towards terrestrial organisms when direct and indirect exposure of the soil compartment is unlikely. Direct release to soil is not intended based on the identified uses of the substance. Exposure of the soil compartment via indirect releases is considered negligible due to the substance properties (low water solubility, low vapour pressure, and ready biodegradability). Thus, only marginal release into the environment is expected and whatever fraction is still released is expected to undergo rapid biodegradation. Thus, the chronic exposure of terrestrial organisms is considered unlikely.

Moreover, neither acute nor chronic terrestrial toxicity is expected based on the aquatic toxicity profile of the substance.

 

 

Intrinsic properties and fate

Isooctadecyl pivalate 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 the substance are likely to be released into the environment if at all.

Furthermore, the substance exhibits a log Koc value of ≥ 4.95 and is poorly water soluble (1.9 - 27 µg/L, mean: 11.7 µg/L). The Guidance on information requirements and chemical safety assessment, Chapter R7.b (ECHA, 2017) 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, 2017) and the rest will be extensively biodegraded (due to ready biodegradability). Thus, discharged concentrations of these substances into the aqueous/sediment compartment are likely negligible.

In consideration of the above, the availability of Isooctadecyl pivalate in the soil environment is expected to be very low, which reduces the probability of chronic exposure of soil organisms in general.

 

Aquatic ecotoxicity data

Available acute data with fish and algae as well as chronic aquatic toxicity tests with algae and aquatic invertebrates showed that no adverse effects occurred in the range of the water solubility (1.9 - 27 µg/L, mean: 11.7 µg/L). Moreover, no toxic effects on activated sludge microorganisms were observed. The results obtained indicate that Isooctadecyl pivalate is not likely to cause toxic effects toward soil organisms either. It is not expected that results from additional studies with soil organisms will lie outside the overall ecotoxicological profile of the substance.

 

Metabolism/Bioaccumulation

After absorption, Isooctadecyl pivalate is expected to be enzymatically hydrolyzed by carboxylesterases yielding the corresponding alcohol and fatty acid. QSAR estimations using BCFBAF v3.01 support the expected rapid biotransformation of this substance. When including biotransformation, BCF and BAF values of 1.24 - 9.87 and 128.4 - 391.4 L/kg, respectively were obtained (Arnot-Gobas estimate, including biotransformation, upper trophic). The metabolism of the hydrolysis products is well established and not of concern in terms of bioaccumulation (for further information see chapter 5.3 of the technical dossier). In summary, Isooctadecyl pivalate is expected to be rapidly hydrolyzed to its respective constituent fatty acid and fatty alcohol. The alcohol hydrolysis product is readily metabolized in aquatic organisms. Pivalic acid has a low potential for bioaccumulation based on a log Kow < 3. Therefore, the overall potential for bioaccumulation is low.

 

Conclusion

Due to its readily biodegradable nature, extensive degradation of the substance in conventional STPs will take place and only low concentrations are expected to be released into the environment, if at all. Once present in the aquatic compartment, further biodegradation will occur and, due to the high log Kow, low water solubility and high adsorption potential, the substance will be bioavailable to soil organisms mainly via feed and contact with suspended organic particles. If uptake by soil-dwelling organisms should occur, extensive and fast biotransformation of the substance into the corresponding fatty acid and alcohol is expected to occur by the action of ubiquitous carboxylesterases. The supporting BCF/BAF values estimated with the BCFBAF v3.01 program, Arnot-Gobas model including biotransformation, also indicate that this substance is not bioaccumulative (BCF clearly < 2000). Furthermore, the available aquatic toxicity data show that no effects occur up to the limit of water solubility. Therefore, Isooctadecyl pivalate is unlikely to pose a risk for soil organisms and testing is thus omitted.