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Fatty acids C16-18 (CAS 67701-03-5) is characterised by a high log Koc (4.12 – 4.71, KOCWIN v2.00) indicating a considerable potential for adsorption to soil particles. As a result of the high adsorption potential of the substance a removal from the water column to a significant degree by adsorption to sewage sludge can be expected (Guidance on information requirements and chemical safety assessment, Chapter R.7b, (ECHA, 2017)). Thus, only limited amounts will get in contact with activated sludge organisms in STPs and the concentration of the substance in effluents of conventional STPs is presumably marginal.

In addition, the substance is determined to be readily biodegradable and according to the Guidance on information requirements and chemical safety assessment, Chapter R.7b (ECHA, 2017), readily biodegradable substances can be expected to undergo rapid and ultimate degradation in most environments, including biological Sewage Treatment Plants (STPs). In addition, no toxic effects on aquatic microorganisms were observed for Fatty acids C16-18 (CAS 67701-03-5). Thus, the degradation process in commercial sewage treatment plants is not suspected to be inhibited by the target substance. Therefore, this substance has a low potential for persistence and chronic exposure of soil organisms is unlikely. In addition, degradation studies cited in the Draft Assessment Report (DAR) for Fatty Acids (C7-C20) (Volume 1, 2008) reported DT50 values of 1.5 to 3 days, indicating rapid primary degradation of fatty acids by microbial organisms in the soil environment. Considering these points, one can assume that the availability of Fatty acids C16-18 (CAS 67701-03-5) in the soil compartment is very low, which reduces the probability of exposure, in particular long-term exposure, of soil organisms in general.

According to ECHA guidance (Chapter R.7c: Endpoint specific guidance, 2017) new long-term testing only needs to be conducted in case the data on aquatic organisms are insufficient to complete the Chemical Safety Assessment and to derive a PNEC soil. Since acute and chronic aquatic toxicity data are available for structurally and chemically closely related source substances for all three trophic levels the Chemical Safety Assessment can be evaluated completely. All reliable aquatic acute and chronic data show no effects up to the water solubility limit. This absence of acute toxicity at > 10 mg/L and chronic or long-term effects in aquatic organisms up to the water solubility limit can be used to adapt the data requirements of Annex X (Chapter R.7c: Endpoint specific guidance, 2017, page 148).

Further, in the Draft Assessment Report (DAR) for Fatty Acids (C7-C20) low toxicity of a fatty acid formulation was demonstrated in several tests on soil macroorganisms, terrestrial non-target arthropods and terrestrial plants (DAR, Volume 1, 2008). These studies prove the negligible effects of fatty acids to terrestrial macroorganisms.

The bioaccumulation potential of Fatty acids C16-18 (CAS 67701-03-5) is expected to be low. For soil-dwelling organisms the main uptake route will be ingestion of contaminated soil particles. For terrestrial plants the main uptake is via pore water, which is expected to be exposed in only limited amounts to Fatty acids C16-18 (CAS 67701-03-5). Fatty acids occur in soils naturally and in the case of ingestion, fatty acids are part of physiological pathways and are used by micro- and macroorganisms as an energy source and for anabolic processes as well. Therefore, fatty acids are generally not considered to be toxic to soil micro- and macroorganisms. If used as an energy source microorganisms degrade the substance to carbon dioxide. In anabolic processes fatty acid carbon is incorporated into the biological matrix of the organism. The suitability as an energy source was demonstrated by the ready biodegradability of the substance, which is used from microorganisms as energy source by degrading the substance to carbon dioxide. Therefore, fatty acids are generally not considered to be harmful either to soil organisms. Hence, in case of exposure to soil, the substance is expected to rapidly dissipate either by degradation or by integration into the organism matrix. Therefore soil is not expected to be a compartment of concern and the risk to soil organisms is negligible.

Based on expected negligible concentrations of the substance in the soil compartment, a low bioavailability, no acute and chronic aquatic toxicity up to the water solubility, negligible reported effects for a fatty acid formulation, low bioaccumulation potential and the use of fatty acids as energy source by organisms, it can be concluded that Fatty acids C16-18 (CAS 67701-03-5) is not expected to show toxicity to terrestrial organisms. Thus, no toxicity tests with terrestrial organisms are considered to be necessary to conclude the Chemical Safety Assessment.