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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), 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), palmic 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 C12 -18 fatty acid mixture (CAS 67701 -01 -3), the main components (fatty acid homologues with a content >10%) are:

- C12: 45 - 65%

- C14: 5 -30%

- C16: 5 - 50%

- C18: < 60%

The evaluation of the risk of the considered fatty acid mixture to aquatic organisms will be 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) could be proved the most toxic component of the mixture C12 - C18 (CAS 67701 -01 -3) 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.

Considering chronic effects of the components available in the C12 - C18 fatty acid mixture, the highest toxicity on aquatic invertebrates is expected from lauric acid (C12) and myristic acid (C14). Myristic acid is of low solubility in water and in the available chronic test on daphnids no effects on reproduction are reported within the range of water solubility. Nevertheless the study reported significant chronic effects at concentrations slightly above the water solubility of the substance given in the report. By taking into account the experimentally determined solubility limits cited under the phys.-chem. chapter of the certain pure fatty acid homologues, chronic effects caused by myristic acid (C14) are unlikely. For lauric acid (C12) which is higher soluble in water chronic effects cannot be excluded as the available study reported significant effects within the range of water solubility.

Due to their low solubility in water, the two other main constituents, palmic acid C16 (CAS 57 -10 -3) and stearic acid C18 (CAS 57 -11 -4), are non-toxic to aquatic organisms.

Thus toxicity of the mixture is expected to be caused by the toxicity of lauric acid (C12) as well as myristic acid (C14).