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Short-term toxicity to fish

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Description of key information

Worst-case LC50 (96 h) expected to be 5.0 mg/L.

Key value for chemical safety assessment

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 fish" for the considered fatty acid mixture.

Fatty acid homologue

LC50(as reported in the study)

Water solubility*

Test design and species

Reference

C12 - CAS 143-07-7
lauric acid

5 mg/L (measured, geom. mean)

4.81 mg/L at 20 °C

96 h, semi-static, Oryzias latipes

NITE, 2001a

C14 - CAS 544-63-8 myristic acid

> 3.2 mg/L (nominal)
> 1.9 mg/L (measured, geom. mean)

< 0.13 mg/L at 20 °C

96 h, semi-static, Oryzias latipes

NITE, 2003a

* see category justification

The homologue C12 (CAS 143-07-7) was tested on rice fish, medaka (Oryzias latipes) (NITE, 2001). The test follows the OECD-guideline 203 and was conducted under GLP in a semi-static system. Nominal test concentrations used in the study were 1.0, 1.7, 3.1, 5.6 and 10.0 mg/L. As test concentrations were analysed, in addition, mean measured concentrations based on geometric mean were given to be < 0.8, 1.2, 1.6, 4.1 and 8.5 mg/L. After 96 h of exposure the LC50-value was determined to be 5.0 mg/L on the basis of mean measured concentrations.

The study available for the pure homologue C14 (myristic acid: CAS 544 -63 -8) was conducted according to OECD 203 following GLP-requirements (NITE, 2003). In the semi-static limit-test rice fish were exposed to 3.2 mg/L of the test substance (purity of the test substance: 98.9%). The resulting LC50 was reported to be higher than 3.2 mg/L (nominal) corresponding to a mean measured value (geometric mean) of > 1.9 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 LC50 -values are far above the limit of water solubility.

In addition to the read-across studies one report is available which describes the effects of a C6 - C20 fatty acid mixture (Scholz, 1993). In this test zebrafish (Danio rerio) were exposed in a semi-static system with different concentrations of the test substance. The study was conducted according to ISO 7346 -1 under GLP-conditions and resulted in an LC50 > 1000 < 3000 mg/L. Nevertheless, as the test substance is not clearly described, the report is regarded as insufficient for evaluation (RL4).

Concluding from the results reported for the pure homologues C12 and C14 a worst-case LC50 of 5.0 mg/L could be expected for the considered mixture based on the toxicity of lauric acid (C12: CAS 143 -07 -7).