Hexadecyl 2-ethylhexanoate

Long-term toxicity to aquatic invertebrates

Description of key information

No adverse effects up to the limit of water solubility (< 0.05 mg/L) for Daphnia magna (OECD 211)

Additional information

No studies investigating the long-term toxicity of Hexadecyl 2-ethylhexanoate (CAS No. 59130-69-7) to aquatic invertebrates are available. Therefore, in accordance to Regulation (EC) No. 1907/2006 Annex XI, 1.5 a read-across to the structurally related source substances C8-16-Fatty acid-2-ethylhexyl ester (CAS No. 135800-37-2) and 2-Ethylhexyloleat (CAS No. 26399-02-0) is conducted.

A read across from C8-16-Fatty acid-2-ethylhexyl ester (CAS No. 135800-37-2) and 2-Ethylhexyloleat (CAS No. 26399-02-0) to Hexadecyl 2-ethylhexanoate (CAS No. 59130-69-7) to cover the long-term toxicity to aquatic invertebrates endpoint is acceptable as first, all substances have common functional groups being fatty acid esters. The fact that the target substance is an ester of 2-ethylhexanoic acid and fatty alcohols with carbon chain lengths of C14 - C18 while the source substances are esters of 2-ethylhexanol and fatty acids with a carbon chain length of C8-C14 and C18, is not considered to invalid the read-across approach. This is assumed due to the similar physico-chemical properties and the common breakdown products of the substances, which are expected to be rapidly metabolised in the body via enzymatic hydrolysis to the starting materials (e.g., see Barron et al. 1999 for metabolism of esters in fish), which then fed into body’s natural catabolic processes, such as ß-oxidation and citric acid cycle (e.g., Rahn et al., 1973; Henderson, 1996). 

All substances are measured or calculated to be insoluble in water and the main components of the substances have similar molecular weights of 368.6 g/mole (CAS No. 59130-69-7), 256.43 – 312.54 g/mole (CAS No. 135800-37-2) and 394.69 g/mole (CAS No. 26399-02-0). The volatility of all substances is low (< 0.0001 Pa at 20 °C). Hence, the behaviour, the fate, the bioaccumulation and thus the toxicity of the substances in the aquatic environment are considered to be identical. 

The study with C8-16-Fatty acid-2-ethylhexyl ester (CAS No. 135800-37-2) was conducted under GLP according to OECD guideline 202, part II using Daphnia magna as test organism (Wierich, 1998). Test concentrations of 1 and 100 mg/L were applied as filtered test solutions. No effects on mortality and reproduction were observed in the 1 mg/L treatment. A significant reduction of reproduction was observed in the 100 mg/L treatment. The authors supposed that the effects in the 100 mg/L treatment was due to a better water soluble by-compound or, less likely, due to a toxic impurity. Hence, the 21d-NOEC is determined to be ≥ 1 mg/L. 

The second study with 2-Ethylhexyloleat (CAS No. 26399-02-0) was also performed under GLP according to OECD guideline 202, part II using Daphnia magna as test organism (Kuech, 1995). Test concentrations of 1 and 100 mg/L were applied as filtered test solutions. Test concentrations were measured to be < 0.01 mg/L in both treatments. No effects on mortality and reproduction were observed in the 1 mg/L treatment. 90% mortality (on day 19) and 23% reduction of reproduction (day 21) was observed in the 100 mg/L treatment. The authors stated that the deaths in the higher concentration could be attributed to sample contamination. Hence, the 21d-NOEC is determined to be ≥ 1 mg/L. 

Due to structural and property similarities to the read-across substances C8-16-Fatty acid-2-ethylhexyl ester (CAS No. 135800-37-2) and 2-Ethylhexyloleat (CAS No. 26399-02-0) these results also apply to Hexadecyl 2-ethylhexanoate (CAS No. 59130-69-7). 

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