Fatty acids, C14-18 and C16-18-unsatd.

Short-term toxicity to fish

Description of key information

A PNEC is not derived since no adverse effects were observed in acute tests in the range of the water solubility of the test substances  (< 0.05 mg/L).

Additional information

Studies are available for the pure homologue members of the fatty acid category. In addition some studies are summarized for certain fatty acid mixtures. Generally it could be stated that acute toxicity of fatty acids to aquatic organisms increases with increasing chain length up to the water solubility limit at a chain length of C12. For longer chains, no acute effects at saturation are observed.

For the C14 - C18 and C16- 18 unsaturated fatty acid mixture (CAS 67701 -06 -8) several acute fish studies are available which were summarized in the following table. In addition, read-across is performed to studies conducted with the pure homologues palmitic acid (C16 - CAS 57 -10 -3) and stearic acid (C18 - CAS 57 -11 -4) which are contained with 5 - 65% and 5 - 55% in the mixture respectively. All available studies conducted with the mixture and the pure homologues were used in a weight of evidence approach to cover the endpoint "short-term toxicity to fish". The results of the studies are summarized in the following table.

Fatty acid	LC50(as reported in the study)	Water solubility*	Test design and species	Reference
C14 - C18 and C16- 18 unsaturated fatty acid mixture - CAS 67701 -06 -8	> 1000 mg/L (nominal)	< 0.05 at 20 °C	96 h, semi-static,Danio rerio	Richterich and Mühlberg, 2001
	> 1000 mg/L (nominal)		48 h, static,Cyprinus carpio	Bogers, 1989a
	> 1000 mg/L (nominal)		48 h, static,Cyprinus carpio	Bogers, 1989b
	> 100 mg/L (nominal)		96 h, semi-static (saltwater),Cyprinodon variegatus	Thomson, 2006
C16 - CAS 57-10-3 palmitic acid	> 1000 mg/L (nominal)	< 0.05 at 20 °C	96 h, semi-static,Danio rerio	Richterich and Mühlberg, 2001b
C18 - CAS 57-11-4 stearic acid	> 10000 mg/L (nominal)	insoluble	48 h, static,Leuciscus idus	Richterich and Mühlberg, 2001c

* see category justification

Mixture studies are available for the freshwater fish species Danio rerio and Cyprinus carpio and the marine species Cyprinodon variegatus (Richterich and Mühlberg 2001, Bogers 1989 and Thomson 2006). The tests were conducted according to OECD 203 or ISO 7346 -1 (freshwater) and OSPARCOM (saltwater) in semi-static or static systems. For the freshwater species a LC50 > 1000 mg/L and for the marine species > 100 mg/L were reported after 48 h and 96 h.

The homologue C16 (palmitic acid: CAS 5 7 -10 -3) was tested on zebrafish (Danio rerio) according to ISO 7346 -1 in a semi-static test (Richterich and Mühlberg, 2001b). In the study nominal concentrations of 0.1, 0.5, 2.8, 16, 90, 250 and 1000 mg/L were tested. No mortality was observed at any test concentration and thus up to the limit of water solubility which is below 0.05 mg/L. In the study the LC50 was reported to be above 1000 mg/L.

The homologue C18 (stearic acid: CAS 57 -11 -4) was tested on golden orfe (Leuciscus idus) (Richterich and Mühlberg, 2001c). In the static test, which was conducted according to DIN 38412/15, the fish were exposed to different concentrations of the test substance (1000, 3000, 10000 mg/L nominal). In the study no effects on fish were reported, resulting in a LC50 > 10000 mg/L.

Concluding from the results reported for the mixture and the pure homologues C16 and C18 no toxicity within the range of water solubility is expected for the considered fatty acid mixture.