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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), the azelaic acid C9 (CAS 123 -99 -9), the decanoic acid C10 (CAS 334 -48 -5), the 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. In case of C8 -24 fatty acids studies are available for algae and microorganisms.

Regarding the composition of the C8 -24 fatty acid mixture (CAS 71076 -48 -7), the main chain lengths (content >10%) are:

- C12: < 30%

- C14: < 30%

- C16: < 30%

- C18: < 30%

- C18': < 35%

- C18'': < 30%

The evaluation of the risk of the considered fatty acid mixture to aquatic organisms is mainly based on studies available for these main components.

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 -24 fatty acids (CAS 71076 -48 -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. For algae no effects up to the limit of water solubility is observed.

Chronic fish toxicity data with the fatty acid mixture 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 mixtureC8 -24 fatty acids (CAS 71076 -48 -7). The chronic toxicity on aquatic invertebrates was assessed based on studies conducted with decanoic acid (CAS 334-48-5) and palmic acid (CAS 57 -11 -4). The study with palmic 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) test programme in cooperation with the Fraunhofer Institute IME (FhG) in Schmallenberg/Germany. Alos 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.

 

Within the fatty acids category, studies describing the toxicity of these substances on microorganisms like Pseudomonas putida are available. For the mixture C8 -24 fatty acids (CAS 71076 -48 -7) read across data from studies on C8, C12, C14, C16 and C18 chain lengths were used. All read across data showed that no toxicity of the substance to microorganisms is expected.

 

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