Hexadecyl 2-ethylhexanoate

Endpoint summary

Additional information

There are no data available for the acute and chronic aquatic toxicity of Hexadecyl 2-ethylhexanoate (CAS No. 59130-69-7). In order to fulfil the standard information requirements set out in Annex VII - IX, 9.1, in accordance with Annex XI, 1.5, of Regulation (EC) No 1907/2006, read-across from structurally related substances was conducted.

In accordance with Article 13 (1) of Regulation (EC) No 1907/2006, "information on intrinsic properties of substances may be generated by means other than tests, provided that the conditions set out in Annex XI are met.” In particular, information shall be generated whenever possible by means other than vertebrate animal tests, which includes the use of information from structurally related substances (grouping or read-across).

Having regard to the general rules for grouping of substances and read-across approach laid down in Annex XI, 1.5, of Regulation (EC) No 1907/2006, whereby substances may be predicted as similar provided that their physicochemical, toxicological and ecotoxicological properties are likely to be similar or follow a regular pattern as a result of structural similarity.

Aquatic Toxicity of the target substance Hexadecyl 2-ethylhexanoate (CAS No. 59130-69-7) and the source substances are presented in the following table.

CAS	59130-69-7	90411-68-0	135800-37-2	26399-02-0
Chemical name	Hexadecyl 2-ethylhexanoate	Hexanoic acid, 2-ethyl, C16-18 alkyl esters	Fatty acids, C8-16, 2-ethylhexyl esters	2-Ethylhexyl oleate
MW	368.6 g/mol	368.6-396.7 g/mol	256.4-396.7 g/mol	394.7 g/mol
Short term toxicity to fish	RA: CAS 90411-68-0	LL50 > 100 mg/L	LC50 > 10000 mg/L
Long term toxicity to fish	Waiving based on CSA	-	-	-
Short term toxicity to aquatic invertebrates	RA: CAS 90411-68-0	EL50 > 100 mg/L	EC50 > 100 mg/L	EC50 > 100 mg/L
Long term toxicity to aquatic invertebrates	RA: CAS 135800-37-2 RA: CAS 26399-02-0	-	NOEC >= 1 mg/L	NOEC >= 1 mg/L
Toxicity to aquatic algae	RA: CAS 90411-68-0	ErL50/ ErL10 > 110 mg/L	ErC50 > 100 mg/L	ErC50 > 100 mg/L
Toxicity to microorganisms	RA: CAS 90411-68-0	NOEC (3 h) ≥ 1000 mg/L	-	-

The above mentioned substances are considered to be similar on the basis of the structural similar properties and/or activities. The available endpoint information of Hexanoic acid, 2-ethyl-, C16-18 alkyl esters (CAS No. 90411-68-0), Fatty acids, C8 -16, 2 -ethylhexyl esters (CAS No. 135800-37-2) and 2 -Ethylhexyl oleate (CAS No. 26399 -02 -0) for acute and chronic aquatic ecotoxicity are used to predict the same endpoints for Hexadecyl 2-ethylhexanoate (CAS No. 59130-69-7).

A detailed analogue approach justification is provided in the technical dossier (see IUCLID Section 13).

Read across acute aquatic ecotoxicity

No studies for the acute toxicity of Hexadecyl 2-ethylhexanoate (CAS No. 59130-69-7) to aquatic fish, invertebrates, algae and microorganisms are available. Therefore in accordance with Article 13 (1) of Regulation (EC) No 1907/2006, a read across to Hexanoic acid, 2-ethyl-, C16-18 alkyl esters (CAS No. 90411-68-0) was applied for acute tests. A read across to Hexanoic acid, 2-ethyl-, C16-18 alkyl esters to Hexadecyl 2-ethylhexanoate to cover the short-term toxicity to fish, invertebrates and algae is acceptable because firstly, both substances have common functional groups being esters of 2-ethylhexanoic acid and fatty alcohols with carbon chain lengths of C16 - C18 and C14 - C18, respectively. Secondly, both substances have the common precursor 2-ethylhexanoic acid and fatty alcohol and common breakdown products as both 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).  Based on their structural similarity, the physico-chemical properties are also similar. Both substances are insoluble in water (< detection limit of used method), feature similar partition coefficients of 5.82 (CAS No. 90411-68-0) and 6.15 (CAS No. 59130-69-7) and the main components of the UVCB substances have similar molecular weights of 368.6 - 396.7 (CAS No. 90411-68-0) and 368.6 (CAS No. 59130-69-7). The volatility of both substances is low (< 0.01 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.

Read across chronic aquatic ecotoxicity

No studies for the acute toxicity of Hexadecyl 2-ethylhexanoate (CAS No. 59130-69-7) to aquatic fish, invertebrates, algae and microorganisms are available. For chronic toxicity to reproduction in invertebrates a read across to C8-16-Fatty acid-2-ethylhexyl ester (CAS No. 135800-37-2) and 2-Ethylhexyloleat (CAS No. 26399-02-0) was applied. A read across to C8-16-Fatty acid-2-ethylhexyl ester (CAS No. 135800-37-2) and 2-Ethylhexyloleat (CAS No. 26399-02-0) to Hexanoic acid, 2-ethyl-, C16-18 alkyl esters (CAS No. 59130-69-7) to cover the long-term toxicity to aquatic invertebrates endpoint is acceptable because firstly, 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 C16 - 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 invalidate 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 feed 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 - 396.7 g/mole (CAS No. 90411-68-0), 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 (< 0.01 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.

Results acute and chronic aquatic ecotoxicity

In all available short-term toxicity tests with Hexanoic acid, 2-ethyl-, C16-18 alkyl esters (CAS No. 90411-68-0), no adverse effects occurred in the range of the water solubility of the substance. The two chronic reproduction tests to Daphnia magna with C8-16-Fatty acid-2-ethylhexyl ester (CAS No. 135800-37-2) and 2-Ethylhexyloleat (CAS No. 26399-02-0) also did not reveal any adverse effects up to the limit of water solubility.

Furthermore, respiration of activated sludge was not inhibited in a 3 hour respiration inhibition test (NOEC ≥ 1000 mg/L, nominal) with source substance Hexanoic acid, 2-ethyl-, C16-18 alkyl esters (CAS No. 90411-68-0). Therefore, disturbances in the biodegradation process of a sewage treatment plant are not anticipated for Hexadecyl 2-ethylhexanoate. Due to the structural and physico-chemical similarities between the target and the read-across source substances Hexanoic acid, 2-ethyl-, C16-18 alkyl esters (CAS No. 90411-68-0), Fatty acid-2-ethylhexyl ester (CAS No. 135800-37-2) and 2-Ethylhexyloleat (CAS No. 26399-02-0) these results also apply to the target substance Hexadecyl 2-ethylhexanoate (CAS No. 59130-69-7).

In summary, Hexadecyl 2-ethylhexanoate (CAS No. 59130-69-7) shows no adverse effects up the limit of water solubility and can thus be considered as not hazardous to the aquatic environment.

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

Justification for non-classification

Based on read-across from the structurally similar substances, the available data on the acute and chronic toxicity to fish, aquatic invertebrates and algae do not meet the classification criteria according to Regulation (EC) 1272/2008 or Directive 67/548/EEC, and are therefore conclusive but not sufficient for classification.