Fatty acids, C18-22

Short-term toxicity to aquatic invertebrates

Description of key information

No short-term toxicity effects up to the limit of water solubility

Additional information

For the fatty acid, C18-22 (CAS 90990-117), which contains as main homologues C18, C20 and C22 no study 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.

Thus, read-across is performed to studies available for the pure homologues stearic acid C18 (CAS 57 -11 -4) and docosanoic acid C22 (CAS 112 -85 -6) for the evaluation of the mixture in a weight of evidence approach.

Fatty acid homologue	EC50(as reported in the study)	Water solubility*	Test design and species	Reference
stearic acid C18	> 32 mg/L (nominal)	< 0.05 mg/L at 25 °C	47 h, static, solvent used, Daphnia magna	Hooftman, 1991
stearic acid C18	> 20 mg/L (nominal)	< 0.05 mg/L at 25 °C	Artemia salina, saltwater (no further information)	Curtis et al.,1970
docosanoic acid C22	> 5.0 mg/L (nominal)	0.016 mg/L at 25 °C	48 h, static, solvent used, Daphnia magna	MOE, 1998

* see category justification

 

For the evaluation of toxic effects of stearic acid C18 on aquatic invertebrates two studies were taken into account. The first static test was conducted on daphnids over 47 hours according to the EU method C.2 in compliance with GLP requirements (Hooftman, 1991). Different concentrations were tested in the study using test water of different hardness. In this study the EC50 -value was reported to be above 32 mg/L (nominal, highest concentration tested). This result is in line with the EC50 given in the other available study for stearic acid C18. In the publication of Curtis et al. (1970) Artemia salina were used as test organisms. The authors reported an EC50 > 20 mg/L. However, the authors did not mention the test duration and hence the study was only rated with a reliability of 4. Nevertheless, the result of the study indicates that no toxic effects were observed with saltwater organisms which is in line to the results obtained from the study with freshwater organisms. Both tests demonstrate the lack of adverse effects in aquatic invertebrates caused by stearic acid.

Docosanoic acid C22 was tested on daphnids in a 48 h static test (MOE, 1998). The study was accomplished according to OECD 202 and in accordance with GLP requirements. Daphnids (Daphnia magna) were exposed to docosanoic acid under static conditions in a limit test. The EC50 (48 h) was determined to be > 5.0 mg/L based on nominal concentrations. Thus no effects could be observed within the range of water solubility, which is determined to be 0.016 mg/L.

Taking into account the results reported for the pure homologues C18 and C22 no toxic effects on invertebrates within the range of water solubility are expected for fatty acids, C18-22.