Fatty acids, C14-18 and C18-unsatd., branched and linear, 2-ethylhexyl esters

Endpoint summary

Description of key information

The “Isostearate 2-ethylhexyl" (=Fatty acids, C14-18 and C18 unsatd., branched and linear, 2-ethylhexyl esters (CAS 85186-76-1)) as the category members, is considered as not bioaccumulable based on the estimated BCF ≤ 173 L/kg whole body w.w. calculated with the BCFWin program (methods based on log Kow and on Arnot-Gobas model). Moreover due to its physico-chemical properties, uptake via water is expected to be low, and on the basis of the calculated BAF in Fish (Arnot-Gobas method) and the available litterature, the “Isostearate 2 -ethylhexyl" ingested through food is quickly hydrolysed by lipases, and the resulting free fatty acids are metabolized by beta-oxydation pathways to generate energy for the cells or reconstituted into glyceride esters and stored in the fat depots in the body of mammals. The beta-oxydation process which allows the metabolisation of fatty acids, takes place in mitochondries and/or peroxysomes and it represents a very common metabolic pathway in numerous organisms, like mammals, fish, mussels and algae.

“Isostearate 2-ethylhexyl" is rapidly metabolized and it does not pose a risk to the organisms in regard to bioaccumulation and biomagnification.

Additional information

No experimental data is available on the bioaccumulation potential of category members. Therefore, all available related data is combined in a Weight of Evidence (WoE), which is in accordance to the REACh Regulation (EC) No 1907/2006, Annex XI General rules for adaptation of the standard testing regime set out in Annexes VII to X, 1.2, to cover the data requirements of Regulation (EC) No. 1907/2007 Annex IX and X (ECHA guidance section R.7.11.5.3, page 121).

Bioaccumulation refers to uptake of a substance from all environmental sources including water, food and sediment. However, the accumulation of a substance in an organism is determined, not only by uptake, but also by distribution, metabolism and excretion. Accumulation takes place if the substance is taken up faster than it can be metabolized and/or excreted.

In the case of the category member (Fatty acids chains from C8 to C18, 2-ethyl-hexyl esters), uptake of dissolved substance via water is expected to be low. The Fatty acids alcohol esters are poorly water soluble, have high adsorption potential (log Koc = 5.9 to 6.5, MCI method, KOCWIN v2.00), but are however all regarded as readily biodegradable. The aqueous environmental concentrations of these substances are therefore assumed to be low, as the substance is assumed to be eliminated in sewage treatment plants to a high extent. If fractions of this chemical were to be released in the aquatic environment, the concentration in the water phase will be reduced by rapid biodegradation and potential of adsorption to solid particles and to sediment. Due to low exposure concentrations through water, no significant uptake through the water phase can therefore be expected.

Food ingestion is likely to be the main uptake route of the category members in fish, since the substance may adsorb to solid particles, which could be potentially ingested by fish. Also for sediment-dwelling organisms the main uptake route will be ingestion of contaminated sediment. In the case of ingestion, category members are predicted to undergo metabolism. Esters of primary alcohols, containing from 1 to 18 carbon atoms, with fatty acids, containing from 2 to 18 carbon atoms, have been shown to be hydrolysed by pancreatic lipases in a study by Mattson and Volpenhein (Mattson and Volpenhein, 1972). Measured rates of enzyme catalysed hydrolysis varied between 2 and 5 µeq/min/mg enzyme for the different chain lengths (IUCLID section 7.1.1, Mattson and Volpenhein, 1972; and references therein). The long esters, like fatty acids C18, isopropyl ester are also expected to be hydrolysed. Only moderate differences in the rate of hydrolysis were observed for different long chain saturated and unsaturated fatty-acid esters, in studies investigating the fatty acid specificity of pancreatic lipases (Macrae and Hammond, 1985; and references therein). Exceptionally poor substrates were esters of fatty acids containing a double bond or a bulky substituent close to the carboxyl group, probably due to steric reasons. And these fatty acids esters are not represented in the category.  Thus they are expected to be hydrolysed by lipases. The resulting free fatty acids and alcohols are absorbed from the intestine into the blood stream. The alcohols are metabolised primarily in the liver through a series of oxidative steps, finally yielding carbon dioxide (Berg, 2001; HSDB)

Fatty acids are either metabolized via the beta-oxidation pathway in order to generate energy for the cell or reconstituted into glyceride esters and stored in the fat depots in the body (Berg et al., 2001). For fatty acids up to C22, beta-oxidation generally takes place in the mitochondria, resulting in the final product acetyl-CoA, which directly enters the citric acids cycle (Berg, 2002).

Peroxisomal β-oxidation has also been shown to take place in fish, mussels and algae (Rocha et al., 2003; and references therein; Frøyland et al., 2000; Bilbao et al., 2009; Winkler et al., 1988).

Metabolic pathways in fish are generally similar to those in mammals. Lipids and their constituents, fatty acids, are in particularly a major organic constituent of fish and play major roles as sources of metabolic energy (Tocher, 2003).

Studies conducted with rats indicate that the main route of excretion in rats is via expired air as CO2, and the second route of excretion is by biliary excretion and faeces. Exemplarily, experimental data of ethyl oleate (the ethyl ester of oleic acid) support this assumption: 14C-labeled carbon of 5 mL/kg of ethyl oleate (CAS No. 111-62-6) was rapidly excreted in respiration CO2 (approximately 70%), faeces (7 -10%), and urine (1-2%), with essentially complete elimination by 72 hours after administration (Bookstaff, 2003).

In conclusion, the category members will be mainly taken up by ingestion and are digested through common metabolic pathways, providing a valuable energy source for the organism, as dietary fats. These substances are thus not expected to bioaccumulate in aquatic or sediment organisms.

Biomagnification are processes that may occur once a chemical is bioaccumulated along the food chain. As these chemical substances are readily biodegradable and are considered to be rapidly metabolized, the category members will not be biomagnified within the food chain.

Hence, as the category members do not pose a risk to organisms in regard to bioaccumulation/biomagnification, in addition to reasons of animal welfare, no further testing is neither required nor proposed. The available literature, supporting the assessment of bioaccumulation are presented in the IUCLID technical dossier and associated chemical safety report in a Weight of Evidence (WoE) approach, which is in accordance to the REACh Regulation (EC) No 1907/2006, Annex XI General rules for adaptation of the standard testing regime set out in Annexes VII to X, 1.2, to cover the data requirements of Regulation (EC) No. 1907/2007 Annex IX and X (ECHA guidance section R.7.11.5.3, page 121).