Fatty acids, C14-22

Long-term toxicity to aquatic invertebrates

Description of key information

Worst-case NOEC (21 d) expected to be 0.31 mg/L (nominal) based on effects of the pure homologue C14 fatty acid.

Additional information

For the members of the fatty acid category four chronic 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 myristic acid (C14) and palmitic acid (C16) are main components of the fatty acid mixture under consideration a read-across is performed to 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. The available NOEC-values are summarized in the following table.

Fatty acid homologue	NOEC (as reported in the study)	Water solubility*	Test design and species	Reference
C14 - CAS 544-63-8 myristic acid	0.31 mg/L (measured, twa concentrations)	< 0.13 at 20 °C	21 d, semi-static,Daphnia magna	NITE, 2003c
C16 - CAS 57-10-3 palmitic acid	0.22 mg/L (measured, twa concentrations)	< 0.05 at 20 °C	21 d, semi-static,Daphnia magna	NITE, 2008
C18 - CAS 57-11-4 stearic acid	--	insoluble	No chronic test available

* see category justification

Myristic acid (C14: CAS 544 -63 -8) was tested in a chronic test according to OECD 211 in compliance with GLP over 21 days (NITE, 2003c). In the study the limit of water solubility under test conditions is reported to be 0.34 mg/L. Due to the low water solubility, a solvent was used to presolve the test material. Different concentrations were tested using a semi-static test design. The study resulted in a measured NOEC of 0.31 mg/L. Thus within the water solubility range given in the study no adverse effects of the test substance on reproduction could be determined. Nevertheless chronic effects of myristic acid cannot completely be excluded as for the test concentration of 0.45 mg/L (measured) and above significant effects are described. Although, chronic effects of myristic acid on daphnids are unlikely to occur, even under consideration of the experimental determined water solubility of < 0.13 mg/L reported for the pure homologue (see category justification) the reported NOEC is taken into account for the evaluation of toxicity of the considered mixture.

For the evaluation of chronic effects of palmic 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 were 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.

Concluding from the results reported for the pure fatty acid homologues C14 and C16 a worst-case NOEC of 0.31 mg/L is assumed for the considered mixture.