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Short-term toxicity to fish

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Description of key information

No effects up to the limit of water solubility based on available data (OECD 203; EU Method C.1).

Key value for chemical safety assessment

Additional information

Since no studies investigating the short-term toxicity of Fatty acids, C16-18, C16-18-alkyl esters (CAS 97404-33-6) to fish are available for this endpoint, in accordance to Regulation (EC) No. 1907/2006 Annex XI, 1.5 a read across to the three structurally related category members decyl oleate (CAS 3687-46-5), dodecyl oleate (CAS 36078-10-1) and Fatty acids, C16-18, C12-18-alkyl esters (CAS 95912-87-1) was conducted. All three read-across substances are characterized by a similar fatty acid (C18 unsatd. and C16-C18 compared to C16-18 of the target substance) and a similar fatty alcohol chain length (C12, C10 and C12/14/16/18 alcohol, respectively compared to C16-C18 of the target substance).The smaller alcohol chain length of the read-across substances increases the water solubility and therefore the bioavailability in the water. Water solubility is negatively correlated with the C-chain length of the fatty alcohol and fatty acid (Lide, 2005). Therefore, it is possible to extrapolate from a category member with higher water solubility since it has an increased bioavailability in the water phase (ECHA, 2008).This read-across is justified in detail in the overall summary (IUCLID Section 6.1) and within the category justification in IUCLID Section 13. In this case of read-across, the best suited (highest degree of structural similarity, nearest physico-chemical properties) read-across substance was used for the assessment. Nevertheless, as it can be seen in the data matrix of the category justification in section 13 and the overall summary, all reliable data in the category support the hazard assessment of each category member by showing a consistent pattern of results.

The first study with the read-across study decyl oleate (CAS 3687-46-5) was performed according to EU Method C.1 under GLP conditions (Scholz, 1994). Brachydanio rerio was exposed to three nominal concentrations up to 10000 mg/L for 96 h. Test solutions were not filtered. Mortality of 70% was recorded after 72 and 96 h at the highest concentration of 10000 mg/L. However, it is reported that the substance floated on top of the water surface and after 24 h the oxygen concentration was lower than the validity criterion stated in the guideline. Therefore, this concentration was disregarded, and the values were not taken into account for assessment, hence the LC50 (96 h) was derived to be > 3000 mg/L of nominal.

The second study with the read-across substance dodecyl oleate (CAS 36078-10-1) was performed according to OECD 203 under GLP conditions with the zebrafish Danio rerio (Hafner, 2013). A limit test with a Water Accommodated Fraction (WAF) of 100 mg/L (nominal) did not result in any mortality after 96 h. Thus, a LL50 (96 h) of > 100 mg/L was derived based on the nominal concentrations. The chemical analysis resulted in concentrations below the analytical detection limit of 0.005 mg/L reflecting the very low water solubility of the test item.

The third study with the read-across substance fatty acids, C16-18, C12-18-alkyl esters (CAS 95912-87-1) was performed according to the EU Method C.1 (GLP) with the zebrafish Brachydanio rerio (Stelter, 1994). A static exposure regime was chosen. Three concentrations of nominal 1000, 3000 and 10000 mg/L were directly applied to the test vessels without a filtration step. Undissolved test material floated on top of the water surface but no effects were observed by the dissolved and even by the undissolved test substance present in the water. Thus, a LC50 (96 h) of > 10000 mg/L (nominal) was derived.

Based on the available result from three structurally related read-across substances (in accordance to Regulation (EC) No 1907/2006 Annex XI, 1.5) which are characterized by a similar ecotoxicological profile and comparable structure, it can be concluded that Fatty acids, C16-18, C16-18-alkyl esters will not exhibit short-term effects to fish up to the limit of water solubility.