10-Undecenoic acid, monoester with 1,2,3-propanetriol

Toxicity to aquatic algae and cyanobacteria

Description of key information

No effects up to the limit of water solubility.

Additional information

Data on the acute toxicity of Glyceryl undecylenate (CAS 123759-97-7) to aquatic algae are not available. The assessment was therefore based on studies conducted with the structurally similar substances Glycerides, C8-10 mono- and di-(CAS 85536-07-8) and Glycerides, C14-18 and C16-18-unsatd. mono-, di- and tri- (CAS 91052-28-7) as part of a read across approach, which is in accordance with Regulation (EC) No. 1907/2006, Annex XI, 1.5. Further justification is given within the overall summary chapter 6.1 and within the analogue justification section 13.

The toxicity of Glycerides, C8-C10, mono- and di- (CAS 85536-07-8) to algae was evaluated in a study by Hafner (2013). This test was conducted according to OECD 201, under GLP conditions. Desmodesmus subspicatus was exposed to the test substance for 72 hours at nominal loading rates ranging from 4.3 to 100 mg/L (WAF). Analytical measurement of test concentrations was performed via TOC and DOC analysis. After the exposure period, significant effects in growth rate were reported at the highest loading rates (45.5 and 100 mg/L, nominal). The resulting EL50 value (72 h) was determined to be 49 mg/L (based on growth rate, loading rate). The NOELR (72 h) was 20.7 mg/L (based on growth rate, loading rate) and 1.19 mg/L (based on growth rate, measured final concentration), respectively.

 Nevertheless, the observed effects might be caused by direct physical interference of test substance particles with algae cells, rather than intrinsic toxicity. For this test, Water Accommodated Fractions (WAFs) were prepared by adding the test material into a defined volume of test medium, stirring for a period of 48 hours, followed by a sedimentation period of 65 minutes. After the sedimentation period, all WAFs contained white flakes, which sedimented. The WAFs were not filtered for the final test. According to the authors of the report, at the highest loading rates (45.5 mg/L and 100 mg/L, for which effects were observed), algae were encased by small dispersed particles in the suspension. This was confirmed by microscopic observation. In the two lower loading rates (4.3 and 9.4 mg/L) no difference compared to the control vessels were observed. In the middle loading rate (20.7 mg/L nominal) cell count was lower and the cell shape was smaller compared to the control. In the second highest loading rate (45.5 mg/L) almost no algal cells could be observed anymore. The remaining cells formed piles which are typical for stress situations. In the highest loading rate (100 mg/L), no algal cells were observed but the whole microscope slide was coated with small oily drops with similar size to that of the algal cells. Therefore, a mechanical disturbance of cells and cell growth cannot be excluded.

Based on the above information, the observed effects are expected to be caused by mechanical disturbance of the algae cells rather than due to intrinsic toxicity of the substance. No toxicity up to the highest attainable solubility (before microemulsion formation) of Glycerides, C8-10 mono- and di- is thus expected.

The second read across study evaluated the toxicity of Glycerides, C14-18 and C16-18 unsaturated, mono-, di- and tri- (CAS 91052-28-7) to algae (Salinas, 2013). This test was conducted according to OECD Guideline 201, under GLP conditions. Desmodesmus subspicatus was exposed for 72 hours to the test substance at test concentrations of 3.2, 10, 32, 100 and 320 mg/L (nominal, loading rate). Chlorophyll-a fluorescence (pulsed excitation with light flashes having a wavelength of 430 nm) was the measured test parameter. Nevertheless, cell density was also determined in order to derive the linear correlation between both parameters. After 72 hours of exposure, effects on algal growth rate were observed at concentrations of 100 mg/L and 320 mg/L, leading to an ErL10 of 172 mg/L and a NOELR of 32 mg/L (nominal, loading rate). The ErL50 was determined to be > 320 mg/L (nominal, loading rate). The reported effects are well above the water solubility of the read across substance (water solubility < 0.05 mg/L) and therefore, they could be caused by physical interference or adsorption between algae and the test substance. Nevertheless, stock solutions were reported to be colourless and clear, and therefore, effects due to toxicity cannot be discarded.

Based on the results for the read-across substances, Glyceryl undecylenate (CAS 123759-97-7) is considered not toxic to aquatic algae within the limit of water solubility.