Fatty acids, C18-22

Toxicity to aquatic algae and cyanobacteria

Description of key information

No toxicity effects up to the limit of water solubility are expected.

Additional information

For fatty acids, C18-22 (CAS 90990-11-7), which contains as main homologues C18, C20 and C20

no toxicity study on algae is available. Therefore ecotoxicological effects are predicted from adequate and reliable data for source substance(s) by read-across to the target substance within the group applying the group concept in accordance with Annex XI, Item 1.5, of Regulation (EC) No 1907/2006.

With regard to the main homologues of Fatty acids, C18 -22 a read-across is prepared to studies conducted with palmitic acid C16 (CAS 57 -10 -3) and docosanoic acid C22 (CAS 112 -85 -6) in a weight of evidence approach.

Fatty acid homologue	ErC50(as reported in the study)	NOEC(as reported in the study)	Water solubility*	Test design and species	Reference
palmitic acid C16	> 0.9 mg/L (initial mean measured)	0.9 mg/L (initial mean measured)	< 0.05 mg/L at 20 °C	72 h, static, solvent used, Pseudokirchneriella subcapitata	MOE 2000
docosanoic acid C22	> 5.0 mg/L nominal	5.0 mg/L nominal	0.016 mg/L at 25 °C	72 h, static, solvent used, Pseudokirchneriella subcapitata	MOE 1998

* see category justification

Palmitic acid C16 was tested on Pseudokirchneriella subcapitata under OECD 201 in a GLP-study (MOE 2000). The test was set up as a limit test, only one test substance concentration was used (10 mg/L nominal, corresponding to 0.9 mg/L initial mean measured), which was above the water solubility limit for this substance. As no effects could be observed at this test concentration, the ErC50(72 h) for growth rate is reported to be above 0.9 mg/L (initial mean measured) and a NOEC of 0.9 mg/L (initial mean measured) was stated.

The homologue docosanoic acid C22 was tested on Pseudokirchneriella subcapitata as well under static conditions in a GLP-study in accordance with OECD 201 (MOE 1998). The test concentration in the limit test (5.0 mg/L nominal) was also above the reported limit of the water solubility of this substance. As no effects could be observed at this test concentration, the ErC50(72 h) for growth rate is reported to be above 5.0 mg/L (nominal) and a NOEC of 5.0 mg/L (nominal) was stated.

 

In the cited tests with palmitic acid C16 and docosanoic acid C22 no effects up to the water solubility limits of the pure homologues were reported. Thus for fatty acids, C18-22 also no toxic effects on algae within the range of water solubility are expected.