Octanoic acid

Endpoint summary

Additional information

Octanoic acid (CAS 124-07-2) has a log Kow of 3.05 (HSDB by Hansch et al. 1995) and a log Koc of 2.05 (ChemProp v6.4, Franco, Fu & Trapp model for ionizable substances, estimated from log Kow of 3.05, pKa of 5.3 and pH 7). Thus, the potential to adsorb or bind onto soil particles is expected to be low. In addition, Octanoic acid (CAS 124-07-2) show no indication that the substance is very toxic, as the EC/LC50 values are > 1 mg/L for algae, daphnia or fish. Thus, according to the Guidance on information requirements and chemical safety assessment, R.7c (ECHA, 2017) Octanoic acid (CAS 124-07-2) is in the soil hazard category 1 which requires a screening assessment of PEC/PNECscreen based on the equilibrium partitioning method (EPM). As the environmental exposure assessment based on a screening PNEC soil (Derived by Equilibrium Partitioning Method (EPM)) indicates no risk for the soil compartment (Risk Characterisation Ratio (RCR) < 1; please refer to Chapter 9 and 10 of the Chemical Safety Report for detailed information), no risk for the soil compartment is indicated.

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). Therefore, this substance has a low potential for persistence and chronic exposure of sediment organisms is unlikely. Further degradation studies cited in the Draft Assessment Report (DAR) for Fatty Acids (C7-C20) (Volume1, 2008) DT50 values of 1.5 to 3 days were reported, indicating rapid primary degradation of fatty acids by microbial organisms in the soil .

Moreover, in the Draft Assessment Report (DAR) for Fatty Acids (C7-C20) (Volume 1, 2008) low toxicity of a fatty acid formulation was demonstrated in several tests on soil macroorganisms, terrestrial non-target arthropods and terrestrial plants. These studies prove the negligible effects of fatty acids to terrestrial macroorganisms. Furthermore, fatty acids occur in sediment and soils naturally and are part of physiological pathways. Fatty acids are used by soil organisms as an energy source and for anabolic processes as well. 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. Moreover, the bioaccumulation potential of Octanoic acid (CAS 124-07-2) is expected to be low i.e. based on log D of 1.34 (pH 7), metabolisation and excretion processes and low BCF values of 225 L/kg after 28 days (OECD 305 E, 1999) from a read-across substance and 83.64 L/kg (EPISuite, BCFBAF, Arnot-Gobas model) based on QSAR. Overall, 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.

According to the Guidance on information requirements and chemical safety assessment, Chapter R.7c (ECHA, 2017), when the substance is readily biodegradable and has a log Kow < 5, the screening assessment showing no risk using aquatic toxicity data (RCR < 1) is sufficient to obviate the need for further information. In addition, low toxicity of a fatty acid formulation was observed in several tests on soil macroorganisms and fatty acids are used by soil organisms as an energy source. Therefore, no soil toxicity tests are needed.