Fatty acids, C8-18

Long-term toxicity to aquatic invertebrates

Description of key information

NOELR (21d) >= 1.3 mg/L (measured, TWA); RA from decanoic acid (CAS 334-48-5)

Additional information

For the members of the fatty acid category four chronic invertebrate tests are available conducted with pure homologues of different chain lengths. The tested homologues were: decanoic acid (C10 - CAS 334-48-5), lauric acid (C12 - CAS 143-07-7), myristic acid (C14 - CAS 544-63-5) and palmitic acid (C16 - CAS 57-10-3). As all substances are main components of the fatty acid mixture C8 –C18 fatty acids (CAS 90990 -08 -2), a read-across was performed to studies available for these pure homologues. The linked studies were used in a weight of evidence approach for the evaluation of effects of the mixture on aquatic invertebrates.

 

For the evaluation of chronic effects of palmitic acid (C16: CAS 57 -11 -4) on aquatic invertebrates, daphnids were tested in a limit-test over a period of 21 days (NITE, 2008). The semi-static experiment was conducted according to OECD 211 in compliance with GLP-requirements. The used test concentration of 0.51 mg/L (nominal) corresponding to a mean measured value (time weighted mean) of 0.22 mg/L was above the reported water solubility limit. No effects could be observed on daphnids at this test concentration and thus the NOEC is reported to be ≥ 0.22 mg/L. As the low NOEC given in the study is only due to the low water solubility of the test substance the value was not used for PNEC-calculation of the considered mixture.

 

A study on the long-term toxicity of lauric acid (CAS 143 -07 -7) to aquatic invertebrates is available. This GLP study (Ministry of the Environment of Japan, 2001) was conducted according to OECD 211 and resulted in a NOEC (21 d) of 0.47 mg/L for Daphnia magna. Since severe deficiencies such as an invalid solvent control, instable test substance concentration, no defined dose-response curve and unknown fate of the test substance had been stated, the study was considered to be disregarded.

 

Furthermore a study on the long-term toxicity of myristic acid (C14: CAS 544 -63 -8) to aquatic invertebrates is available. The test was conducted according to OECD 211 in compliance with GLP over 21 days (NITE, 2003c). Due to the low water solubility, a solvent was used to presolve the test material. The study resulted in a measured NOEC of 0.31 mg/L. The reliability of the study results regarding the measured concentrations compared to the limit of water solubility are under discussion and therefore not taken into account for assessment.

 

In order to overcome methodological deficiencies in the studies, a test programme was setup in cooperation with the Fraunhofer Institute IME (FhG) in Schmallenberg/Germany. In the frame of this programme a new OECD 211 study with decanoic acid (CAS 334 -48 -5) was performed. The study was set up as limit test, in which the test item was prepared as WAF with a nominal loading of 5 mg/L and the medium was replaced daily. Samples were taken for chemical analysis from fresh and aged media during three representative 24 hours exposure periods per week. No immobilisation of daphnia occurred throughout the test, neither the mean cumulative offspring was affected. Based on the measured time weighted average concentration (TWA), a NOELR >= 1.3 mg/L has been determined (corresponding to the nominal load of 5 mg/L).

 

This result is currently used as read across to chronic daphnia toxicity of C8 –C18 fatty acids (CAS 90990 -08 -2). A detailed justification for the grouping of chemicals and read-across is provided in the Category Justification (see section 13 of the technical dossier).

 

Within the above mentioned test programme a new OECD 211 chronic toxicity study with lauric acid is in progress in order to overcome methodological deficiencies due to rapid decay of the test substance and to verify the hazard assessment.