Fatty acids, C16, C18 and C18-unsaturated, C12-15 alcohol (linear and branched), esters

Endpoint summary

Additional information

There are no experimental studies available, in which the terrestrial toxicity of the target substance target substance Fatty acids, C16, C18 and C18-unsaturated, C12-15 alcohol (linear and branched), esters was investigated. Therefore, the terrestrial toxicity of the target substance was assessed on the basis of literature data and a read-across approach, through which additional data from a structurally and chemically closely related source substance was compiled in order to fulfill the standard information requirements laid down in Annex XI of REACh Regulation (EC) No 1907/2006. Read-across was performed in accordance with Regulation (EC) No 1907/2006 Annex XI, 1.5.

 

According to Article 13 of Regulation (EC) No 1907/2006 "General Requirements for Generation of Information on Intrinsic Properties of substances", information on intrinsic properties of substances may be generated by means other than tests e.g. from information from structurally related substances (grouping or read-across), provided that conditions set out in Annex XI are met. In Annex XI, "General rules for adaptation of this standard testing regime set out in Annexes VII to X”, it is stated that “substances whose physicochemical, toxicological and ecotoxicological properties are likely to be similar or follow a regular pattern as a result of structural similarity may be considered as a group, or ‘category’ of substances. This avoids the need to test every substance for every endpoint and avoids unnecessary animal testing”.

In the present dossier, the source substance for read-across was selected on the basis of structural similarities and similarities in properties and/or activities to the target substance, with due regard of the requirements for adequacy and reliability of data. Based on the high degree of similarity between the structural and physico-chemical properties of the target and source substance, it is assumed that the target substance will exhibit a similar ecotoxicological profile as the selected source substance, which is thus considered a suitable representative for the assessment of the terrestrial toxicity of the target substance.The selected source substance 2-octyldodecyl isooctadecanoate (CAS 93803-87-3) is a UVCB, characterized by a long-chain fatty acid (C18iso) and a branched fatty alcohol component with a chain length of C20, covering esters in approximately the same size range as in the target substance. Therefore, most of the data gaps can be covered by interpolation from source substance data in accordance with Annex XI, Item 1.5, of Regulation (EC) No 1907/2006. A detailed read-across justification is provided in IUCLID section 13.

 

Environmental fate

The target substance is characterized by low water solubility (< 6.57 µg/L at 20 °C, pH 6.3, OECD 105), low vapour pressure (<0.00001 Pa at 20 °C, ARChem SPARC, version 4.6), a high potential for adsorption to organic soil and sediment particles (log Koc > 5.0, 25 °C, KOCWIN v2.00) and ready biodegradability.

Based on these properties, evaporation into air is not expected and soil and sediment are expected to be the main compartments for environmental distribution. However, readily biodegradable substances are eliminated in sewage treatment plants to a high extent. Therefore, release to the aquatic environment and exposure of sediment is highly unlikely in the first place and persistence in the aquatic and terrestrial environment is not of concern. Indirect exposure of soil via irrigation or atmospheric transport is not expected either based on the physico-chemical substance properties (water solubility < 0.05 mg/L and vapour pressure < 0.00001 Pa).

Thus, the overall bioavailability of the target substance in surface water is expected to be low and the most relevant route of uptake by aquatic and terrestrial organisms is expected to occur via ingestion of particle-bound substance. However, the bioavailability in sediment and soil is presumably low based on the high sorption potential on the one hand as well as on metabolization pathways on the other hand. Generally, long-chain aliphatic esters can be expected to be metabolized by microorganisms. Literature provides evidence that long-chain aliphatic esters undergo common metabolic pathways and are excreted or used as energy source for catabolism by both aquatic and terrestrial microorganisms.

Therefore, the bioavailability in sediment and soil is presumably low, thereby reducing the probability of chronic exposure.

Aquatic and terrestrial hazard

Based on the available aquatic short-term and long-term aquatic toxicity data (i.e. fish, invertebrates, algae and microorganisms) the substance is not hazardous to aquatic organisms up to the limit of water solubility (< 6.57 µg/L,at 20 °C, pH 6.3).

For the toxicity to aquatic microorganisms, one study is available with the source substanceDodecyl oleate(CAS 36078-10-1) which was conducted according to OECD guideline 209 and GLP. No inhibition of the respiration rates of aquatic microorganisms was observed. The Guidance Document (ECHA Chapter R.7c, 2017) states that a test on soil microbial activity will only be additionally necessary for a valid PNEC derivation if inhibition of sewage sludge microbial activity has occurred and this is clearly not the case. Thus, it is concluded that the target substance neither causes toxic effects to aquatic nor soil microorganisms. This conclusion is corroborated by further evidence from literature according to which soil microorganism communities are capable of degrading fatty acid esters (Hita et al., 1996 and Cecutti et al., 2002) and even using them as energy source (Banchio & Gramajo, 1997). Based on the available information, effects on soil microorganisms are not expected to be of concern, and consequently, no further testing is required.

For the further assessment of the hazard to terrestrial organisms, long-term testing was considered necessary due to the high adsorption potential of the substance (log Koc > 5.0). Earthworm studies evaluate exposure via soil pore water, surface contact and ingestion of soil particles.

One experimental earthworm study is available for the closely related source substance 2-octyldodecyl isooctadecanoate (CAS 93803-87-3), which is characterized by a long-chain fatty acid (C18iso) and a branched fatty alcohol component with a chain length of C20, covering esters in approximately the same size range as in the target substance. It has a very high potential for adsorption to soil particles (log Koc = 10.49), comparable to the target substance and therefore adequately covers potential uptake via ingestion.Therefore, most of the data gaps can be covered by interpolation.

In the available study, which was conducted according to OECD guideline 222, no significant effects on earthworm reproduction were recorded after 56 d, resulting in a NOEC (56 d) of ≥ 1000 mg/kg soil dw. Thus, it is concluded that the terrestrial toxicity of the target substance to soil macroorganisms except arthropods is low.

In the unlikely event of absorption by organisms, long-chain aliphatic esters are expected to be rapidly metabolized by carboxylesterases. Carboxylesterases are a common family of enzymes present in a wide variety of organisms, including invertebrates and mammals that enzymatically hydrolyze esters into their corresponding free fatty acids and alcohols. Furthermore, it is well established that the resulting hydrolysis products (free fatty acids and alcohols) are also readily metabolized by aquatic and terrestrial organisms and are therefore not of concern in terms of bioaccumulation (refer to section 5.3 for further details). QSAR estimations using BCFBAF v3.0 support the expected rapid biotransformation of this substance with BCF values in the range of 0.90 to 22.7 L/kg.

Therefore, the overall potential for bioaccumulation is expected to be low.

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