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Toxicity to microorganisms

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Description of key information

No toxicity is expected for microorganisms. 

Key value for chemical safety assessment

Additional information

Within the fatty acid category studies describing the toxicity of fatty acids to Pseudomonas putida are available. For the mixture under discussion five studies were used as read-across from C8, C12, C14, C16 and C18 fatty acids

For the octanoic acid C8 (CAS 124 -07 -2) and the stearic acid C18 (CAS 57 -11 -4) cell multiplication inhibition tests were conducted following GLP-requirements. The used method in the tests was similar to the ISO guideline 10712. In the study available for octanoic acid an EC10 (18 h) of 912 mg/L (nominal) was reported (Coenen, 1988). Testing of stearic acid resulted in an EC10 (18 h) of 883 mg/L (nominal) (Coenen, 1989). Concluding from the results of both studies both substances are regarded to be not toxic to microorganisms up to their water solubility limit. Octanoic acid (C8) is highly soluble in water (680 mg/L - 789 mg/L). In contrast stearic acid (C18) is nearly insoluble in water (< 0.05 mg/L). Thus as relevant EC10 value for PNEC-calculation 912 mg/L is used.

In addition tests was conducted with lauric acid C12 (CAS 143 -07 -7), myristic acid C14 (544 -63 -5) and palmitic acid C16 (CAS 57 -10 -3) on Pseudomonas putida according to DIN 38472 Part 27 (Geisel and Berger, 1998 and Kirch 1994a/b). In these test EC10 of >1000 mg/L were reported after 30 min exposure based on respiration rate for all tested substances. Though these tests do not meet the requirements of todays standard procedures the results are considered reliable to demonstrate the low toxicity of the test substance to microorganisms.

All available tests for the pure homologues were used for a weight of evidence approach for the fatty acid mixture under consideration.