Hexadecyl 2-ethylhexanoate

Toxicity to soil microorganisms

Additional information

No studies investigating the toxicity to soil organisms is available for Hexadecyl 2-ethylhexanoate (CAS No. 59130-69-7). However, for the read across substance Hexanoic acid, 2-ethyl-, C16-18 alkyl esters (CAS No. 90411-68-0) an OECD 207 guideline study is available (Harris, 2013). The test organism Eisenia fetida was exposed to the test substance in artificial soil for 14 days, at the nominal test concentration 1000 mg/kg. No mortality occurred during the test period. Hence, the test substance is not expected to have effects on soil macroorganisms. No further experimental data evaluating the toxicity to soil organisms is available for Hexadecyl 2-ethylhexanoate (CAS No. 59130-69-7). Due to the ready biodegradability of the substance only negligible amounts, if at all, are expected to be present in the terrestrial compartment. Therefore chronic exposure of terrestrial 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 Hexadecyl 2-ethylhexanoate (CAS No. 59130-69-7) is not bioaccumulative. Based on the available information, toxicity to terrestrial macroorganisms is not expected to be of concern.

Intrinsic properties and fate/ exposure

Hexadecyl 2-ethylhexanoate (CAS No. 59130-69-7) 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, 2012b).Therefore, after passing through conventional STPs, only low concentrations of these substances are likely to be (if at all) released into the environment.

Furthermore, the substance exhibits a log Koc value > 6 and is poorly water soluble (< 0.05 mg/L measured in aqua dest).The Guidance on information requirements and chemical safety assessment, Chapter R.7b (ECHA, 2012b) 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, 2012a) and the rest will be extensively biodegraded (due to ready biodegradability). Thus, discharged concentrations of these substances into the aqueous compartment are likely to be very low. If direct/indirect application of the substances occurs (indirect via sludge application) will occur, the substance will again be rapidly degraded until ultimate biodegradation.

Aquatic and terrestrial ecotoxicity data

Acute and chronic aquatic toxicity tests of the analogue substances Hexanoic acid, 2-ethyl-, C16-18 alkyl esters (CAS No. 90411-68-0), C8-16-Fatty acid-2-ethylhexyl ester (CAS No. 135800-37-2) and 2-Ethylhexyloleat (CAS No. 26399-02-0) to fish, invertebrates, algae and microorganisms showed no adverse effects occurred. The obtained results indicate that Hexadecyl 2-ethylhexanoate (CAS No. 59130-69-7) is likely to show no toxicity to terrestrial organisms as well. However, for the read across substance Hexanoic acid, 2-ethyl-, C16-18 alkyl esters (CAS No. 90411-68-0) an OECD 207 guideline study is currently ongoing. The dossier of Hexadecyl 2-ethylhexanoate (CAS No. 59130-69-7) will be updated as soon as possible and the Chemical Safety Assessment according to Annex I of Regulation (EC) No 1907/2006 will be re-evaluated based on the outcome of this new study.

Metabolisms/Bioaccumulation

After absorption, to Hexadecyl 2-ethylhexanoate (CAS No. 59130-69-7) is expected to be enzymatically hydrolysed in vivo by the ubiquitary enzyme carboxylesterase, yielding the corresponding alcohols and 2-ethylhexanoic acid. QSAR estimations using BCFBAF v3.0 support the expected rapid biotransformation of this substance with BCF/BAF values of <= 120 L/kg, respectively (Arnot-Gobas estimation including biotransformation, upper trophic level).

The metabolism of the hydrolysis products: alcohol (i.e. Cetyl alcohol) and 2-ethylhexanoic acid is well established and not of concern in terms of bioaccumulation (for further information see chapter 5.3 of the technical dossier).

Summarizing, Hexadecyl 2-ethylhexanoate (CAS No. 59130-69-7) is expected to be rapidly hydrolyzed to 2-ethylhexanoic acid and Cetyl alcohol. Both hydrolysis products are supposed to be satisfactory metabolized in organisms and are not bioaccumulative. Therefore, no potential for bioaccumulation is to be expected.

Conclusion

Hexadecyl 2-ethylhexanoate (CAS No. 59130-69-7) is unlikely to pose a risk for terrestrial organisms based on a) the lack of chronic exposure due the ready biodegradation and b) the low toxicity as expected for this substance for terrestrial organisms based the lack of adverse effects in aquatic ecotoxicity tests and an acute test to earthworm. Therefore, no further tests on terrestrial organisms are provided.

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