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Toxicity to aquatic algae and cyanobacteria

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Description of key information

No toxic effects up to the limit of water solubility for Scenedesmus subspicatus (DIN 38412, Part 9)

Key value for chemical safety assessment

Additional information

There are no studies on algal toxicity available for 2-ethylhexyl stearate (CAS No. 22047-49-0). The assessment was therefore based on studies conducted with the structurally most similar substances, for which data is available, 2-ethylhexyl oleate (CAS No. 26399-02-0), isopropyl myristate (CAS No. 110-27-0) and Fatty acids, C16-18, 2-ethylhexylester (CAS No. 91031-48-0) as part of a read across approach. This is in accordance with Regulation (EC) No 1907/2006, Annex XI, 1.5. Grouping of substance and read across approach. Further justification is given within the endpoint summary 6.1 and within the category justification section 13. In this case of read-across, the best suited (highest degree of similarity, nearest physico-chemical properties) read-across substances were entered into IUCLID. Nevertheless, as can be seen in the data matrix of the category justification in Section 13, all reliable data in the category support the hazard assessment for this endpoint, by showing a consistent pattern of results.

The key study with isopropyl myristate (CAS No. 110-27-0) was performed as a limit test according to the EU Method C.3 and GLP (Rieche, 1995). The test organism Scenedesmus subspicatus was exposed to the test substance in a static system for 72 hours, at the nominal test concentration of 100 mg/L. The test was performed with and without separation of undissolved test substance. With undissolved test substance present, algal growth was significantly inhibited. However, when the undissolved phase was separated, no effects on growth were observed. It can, therefore, be concluded that the substance has no toxic effects on the test organism up to the limit of water solubility.

The key study with 2-ethylhexyl oleate (CAS No. 26399-02-0) was performed as a limit test according to the EU Method C.3 and GLP (Rieche, 1995). The test organism Scenedesmus subspicatus was exposed to the test substance in a static system for 72 hours, at the nominal test concentration 100 mg/L. The test was performed with and without separation of undissolved test substance. With undissolved test substance present, algal growth was significantly inhibited. However, when the undissolved phase was separated, no effects on growth were observed. It can, therefore, be concluded that the substance has no toxic effects on the test organism within the range of water solubility.

The supporting study with Fatty acids, C16-18, 2-ethylhexylester (CAS No. 91031-48-0) was performed according to the guideline DIN 38412, Part 9 and GLP (Kläs, 1994). A culture of the test organism Scenedesmus subspicatus was exposed to the test substance in a static system for 96 hours, at nominal test concentrations of 0, 30, 100 and 300 mg/L. After 72 hours no inhibition of growth was observed at any treatment, but an increase of 1.4 – 11.4%. After 96 h 10.9% inhibition was observed at 100 mg/L, but no inhibition at 300 mg/L. Since there is no proper concentration-effect relationship, the effect is assumed to be rather physical than systemic, possibly caused by the presence of undissolved test material. The reported EC50 of 300 mg/L and NOEC of 30 – 100 mg/L were derived, based on effects on biomass. However, since the values were derived from a probit analysis with two points only, they are not considered reliable. Additionally, biomass is a very sensitive and species specific parameter, and it is therefore recommended to use growth rate as parameter for assessment of toxicity. Although no reliable EC50 value can be derived from the study, it is clear that no inhibition of growth occurred after 72 hours of exposure.

Thus, based on theabove mentioned results, and due to the structural and profile similarities of the substances, as are explained with in the overall endpoint summary 6.1 it can be concluded that no toxicological effects on algae are expected up tothe limit ofwater solubility for 2-ethylhexyl stearate (CAS No. 22047-49-0).