Fatty acids, soya, 2-ethylhexyl esters

Toxicity to soil microorganisms

Description of key information

No data available. Considering all relevant information available, toxicity to soil microorganisms is not expected.

Additional information

Experimental data on the toxicity of Fatty acids, soya, 2-ethylhexyl esters (CAS 93572-14-6) to terrestrial microorganisms are not available. Based on the available data a toxicity of the substance to microorganisms is not expected. The substance is considered to be readily biodegradable and not toxic to aquatic microorganisms. Furthermore a rapid and extensive removal of the substance in sewage treatment plants can be expected. Furthermore the Guidance on information requirements and chemical safety assessment, Chapter R7.b (ECHA, 2012) 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. Due to the high log Koc a significant degree of removal of these substances from the water column due to adsorption can be expected (Guidance on information requirements and chemical safety assessment, Chapter R.7a (ECHA, 2012)). Consequently a significant release to the environment of the substance via STP effluents is not expected and thus an exposure of terrestrial organisms is unlikely. However, when terrestrial organisms are exposed to the substance toxic effects are not expected as demonstrated by the available study on the acute toxicity to terrestrial macrororganisms. Based on the acute test conducted with structurally analogue substance isopropyl myristate (CAS No. 110-27-0) on Eisenia fetida toxic effects on soil organisms are not expected. The substance caused no mortality and thus an EC50 > 20000 mg/kg was reported for the read across substances.
In accordance with Regulation (EC) No. 1907/2006, Annex X, Column 2, 9.4 further studies on the effects on terrestrial organisms do not have to be conducted since the chemical safety assessment indicates that toxicity to soil microorganisms is not expected to be of concern.

This is supported by further evidence from literature data. This data showed that soil microorganism communities are well capable of degrading fatty acid esters (Hita et al., 1996 and Cecutti et al., 2002) and use them as energy source (Banchio & Gramajo, 1997). Hita et al. (1996) investigated the degradation of the model molecule tristearin which is a triglyceride containing of glycerin tri-esterified with stearic acid in three different soils for 4 weeks. The amount of stearic acid increased in considerable amounts during the experiment showing the hydrolytic activity of lipases breaking the ester bonds. The investigation of ester fractions moreover showed the generation of new alkanoic acids (methyl stearate, ethyl stearate and propyl stearate) which were not determined in the controls. Nevertheless the amounts were no longer present after 4 weeks, which leads to the assumption that degradation by soil microorganisms had occurred. Comparable results were demonstrated by Cecutti et al. (2002). The authors incubated a soil sample with methyl oleate (plant oil) for 120 d. Methyl oleate and its metabolites were completely degraded after 60 d. Streptomyces coelicolor, a common gram-positive soil bacterium uses fatty acids (C4-C18) as sole carbon end energy source indicating that fatty acids are not-toxic and can be used for catabolism (Banchio and Gramajo, 1997). The available literature data shows that soil microorganisms are capable to break-up ester bonds and degrade fatty acids in significant amounts. Moreover, the data indicated the non-toxic properties of fatty acids since they can be used as energy source without adverse toxic effects occuring.

Therefore, as a part of 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, one can conclude from all available literature and data that due to a) the observed absence of toxicological effects on aquatic organisms, b) the lack of chronic exposure and c) the, acknowledged metabolisation of fatty acid esters, terrestrial toxicity, and in particular toxicity to soil microorganisms, is not of concern.