Fatty acids, C8-16

Short-term toxicity to aquatic invertebrates

Description of key information

Worst-case EC50 (48 h) expected to be 3.6 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 fatty acid mixture under consideration, which contains as main constituents C12 and C14, read-across is performed to studies available for the pure homologues C12 (lauric acid, CAS 143 -07 -7) and C14 (myristic acid, CAS 544 -63 -3). For the evaluation of the mixture only studies available for the pure homologues which were determined as key studies were chosen for read-across. All linked studies conducted with the pure homologues were used in a weight of evidence approach to cover the endpoint "short-term toxicity to invertebrates" for the considered fatty acid mixture.

Fatty acid homologue	EC50(as reported in the study)	Water solubility*	Test design and species	Reference
C12 - CAS 143-07-7 lauric acid	3.6 mg/L (measured, geom. mean)	4.81 mg/L at 20 °C	48 h, semi-static, Daphnia magna	NITE, 2001
C14 - CAS 544-63-8 myristic acid	> 3.2 mg/L (nominal) > 1.7 mg/L (measured, geom. mean)	< 0.13 at 20 °C	48 h, semi-static, Daphnia magna	NITE, 2003b

* see category justification

In the study conducted with lauric acid (C12: CAS 143 -07 -7) according to the OECD guideline 202, daphnids were exposed in a dose-response experiment under GLP-conditions (Anonymous, NITE, 2001). In the semi-static test an EC50 of 3.6 mg/L (mean measured - geometric mean) was determined.

The study available for myristic acid (C14: CAS 544 -63 -8) was conducted according to OECD 202 following GLP-requirements (NITE, 2003b). In the semi-static limit-test daphnids were exposed to 3.2 mg/L of the test substance (purity of the test substance: 98.9%). The resulting EC50 was reported to be higher than 3.2 mg/L (nominal) corresponding to a mean measured value (geometric mean) of > 1.7 mg/L. Nevertheless in the study higher water solubility is given than that mentioned in the table above (0.34 mg/L vs. < 0.13 mg/L) the reported EC50 -values are far above the limit of water solubility.

Concluding from the results reported for the pure homologues C12 and C14, effects on invertebrates within the water solubility are only expected for the C12 homologue (lauric acid). For the other homologue (C14) contained in the mixture no effects up to the limit of water solubility are reported. Thus a worst-case EC50 of 3.6 mg/L is assumed.