Fatty acids, C8-18 and C18-unsatd.

Endpoint summary

Additional information

The aquatic toxicity of fatty acids has been evaluated in studies on fish, daphnids and algae as well as microorganisms. Most of the studies were conducted with fatty acid homologues. Most tests are available for the soluble fatty acids octanoic acid C8 (CAS 124 -078 -2), azelaic acid C9 (CAS 123 -99 -9), decanoic acid C10 (CAS 334 -48 -5) and lauric acid C12 (CAS 143 -07 -7). In addition some studies were conducted with the insoluble pure homologues myristic acid C14 (CAS 544 -63 -8), palmitic acid C16 (CAS 57 -10 -3) and stearic acid C18 (CAS 57 -11 -4) and certain mixtures of the fatty acid category.

Regarding the composition of the C8 -18 and C18 -unsaturated fatty acid mixture (CAS 67701 -05 -7), the main components (fatty acid homologues with a content >10%) are:

- C12: 45 - 65%

- C14: 10 -25%

- C16: 5 - 15%

- C18 (unsaturated): 5 - 20%

The evaluation of the risk of the considered fatty acid mixture to aquatic organisms is mainly based on studies available for these main components. A detailed justification for the grouping of chemicals and read-across is provided in section 13 of the technical dossier.

Regarding the acute toxicity of fatty acids to aquatic organisms, lauric acid (C12: CAS 143-07-7) is the most toxic component of the mixture C8 - C18 and C18 -unsatd. fatty acids (CAS 67701 -05 -7), as it is the most soluble homologue contained in the mixture. Regarding the acute toxicity, aquatic invertebrates are most sensitive to lauric acid, followed by fish. Regarding algae no effects up to the limit of water solubility is observed. Since only for acute fish toxicity data for Fatty acids, C8 -18 and C18 -unsatd. are available, also for this endpoint information on the main constituents is additionally taken into account.

Chronic fish toxicity data with C8 -18 and C18 -unsaturated fatty acid mixture (CAS 67701 -05 -7) are not available. Therefore data from a surrogate substance, sodium laurate (CAS 629-25-4, C12), were taken into account. From this test it was concluded, that long-term effects on fish up to the limit of water solubility are not expected for the mixture C8 -18 and C18 –unsaturated fatty acids. The chronic toxicity on aquatic invertebrates was assessed based on studies conducted with decanoic acid (CAS 334-48-5) and palmitic acid (CAS 57-11-4). The study with palmitic acid did not show any effects on aquatic invertebrates. The study with the more water soluble decanoic acid (CAS 334-48-5) was performed within (an ongoing) a test programme in cooperation with the Fraunhofer Institute IME (FhG) in Schmallenberg/Germany. Also in this test no immobilisation occurred throughout the test, neither the mean cumulative offspring was affected by the test substance. A NOELR of >= 1.3 mg/L (measured, TWA) was determined, which corresponds to a nominal loading of 5 mg/L. An additional study on chronic invertebrate toxicity of lauric acid, which was designed to overcome methodological deficiencies and revise the environmental hazard, is still ongoing.

Palmitic acid C16 (CAS 57 -10 -3) and stearic acid C18 (CAS 57 -11 -4), are generally not expected to be toxic to aquatic organisms, due to their low water solubility.

One study was available testing the toxicity of fatty acids, C8 -18 and C18 –unsaturated to microorganisms. Read across data from five further studies on C8, C12, C14, C16 and C18 chain lengths were additionally used for assessment. All data showed that no toxicity of the substance to microorganisms is expected.