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Toxicity to aquatic algae and cyanobacteria

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In the toxicity to aquatic algae test the median effect concentration with respect to growth rate (ErC50 /0-3 days) of the test substance 2-Propenoic acid, C16-18-alkyl esters (read across) was calculated to be 278 mg/L and the yield (EyC50/0–3 days) was calculated to be 181 mg/L based on the loading rate. The no-observed-effect concentration (NOEC) with respect to growth rate and yield was 100 mg/L loading rate.

In an algae growth inhibition study, water accommodated fractions of the test substance 2 -Propenoic acid, C18-26-alkyl ester were tested on their effects on the growth of the freshwater green alga Desmodesmus subspicatus over the period of 72 hours. The observed dose-response relationship was ambiguous. Therefore, no calculation of effect loading (EL) values was possible. Instead, EL-values were approximated directly from the observation data.
The EL50 basic for effect growth rate (72 h) was greater than 100 mg/L.

Based on this result with respect to the growth rate and yield of 2-Propenoic acid, docosyl ester is also considered to be >100 mg/L.

Key value for chemical safety assessment

Additional information

The toxicity to aquatic algae test was conducted according to the OECD guideline 201. The median growth inhibiting concentration (ErC50/EyC50) and the low-effect concentrations (ErC10/EyC10,ErC20/EyC20), based on the average specific growth rate and the yield (algal biomass production) within 3 days, of 2-Propenoic acid, C16-18-alkyl esters to the green alga Desmodesmus subspicatus, were investigated over a period of 72 h. The nominal concentrations of the test substance were 1.0, 3.2, 10, 32, 100 and 320 mg/L. These test concentrations were prepared using the water accommodated fraction (WAF) approach. Three parallel test vessels were used for each concentration of the test substance. GC-FID analyses of the test substance concentrations were conducted at the beginning and at the end of the exposure period. The analysis revealed that all test substance concentrations were below the quantification limit (<0.02 mg/L). Thus, the evaluation was based on the nominal loading rates.

With respect to algal growth rate inhibition, the following significant effects as compared to the untreated controls were observed at the respective nominal loading rates: 320 mg/L (65%), 10 mg/L (8%). No significant effects (determined by Dunnett’s Test) were observed at all other test concentrations. No significant effects were observed at the loading rates of 32 and 100 mg/L, and therefore, it can be concluded, that the observed effects at the loading rate of 10 mg/L were presumably due to an artifact. Thus, these results were excluded from the evaluation.

Based on these data, the median effect concentration with respect to growth rate (ErC50 /0-3 days) of the test substance to Desmodesmus subspicatus was calculated to be 278 mg/L loading rate (95% confidence limits: 212-296 mg/L). The low effect concentrations with respect to growth rate, ErC10 and ErC20, were 169 mg/L (95% confidence limits: 49.3–218 mg/L) and 203 mg/L (95% confidence limits: 84.5-244 mg/L), respectively. The no-observed-effect concentration with respect to growth rate (NOErC) was 100 mg/L loading rate. For the endpoint yield (biomass production), the following significant effects as compared to the untreated controls were observed at the respective loading rates: 320 mg/L (95%), 10 mg/L (29%). No significant effects (determined by Dunnett’s Test) were observed at all other test concentrations. No significant effects were observed at the loading rates of 32 and 100 mg/L, and therefore, it can be concluded, that the observed effects at the loading rate of 10 mg/L were presumably due to an artifact. Thus, these results were excluded from the evaluation. Based on these data, the median effect concentration with respect to yield (EyC50/0–3 days) of the test substance to Desmodesmus subspicatus was calculated to be 181 mg/L loading rate (95% confidence limits: 1140-230 mg/L). The low effect concentrations with respect to yield, EyC10 and EyC20, were 117 mg/L (95% confidence limits: 76.7-150 mg/L) and 138 mg/L (95% confidence limits: 97.0-173 mg/L), respectively. The no-observed-effect concentration with respect to yield (NOEyC) was 100 mg/L loading rate.

The toxicity of the test substance 2 -Propenoic acid, C18-26-alkyl ester to the unicellular freshwater green alga Desmodesmus subspicatus was determined according to the principles of OECD 201. The aim of the study was to assess the effects on growth rate and yield over a period of 72 hours. The study was conducted under static conditions with an initial cell density of 4910 cells/mL. Based on a preliminary test, 9 water accommodated fractions (WAF) were tested in a geometrical series with a dilution factor of V10, nominal: 0.0100 - 0.0320 - 0.100 - 0.320 - 1.00 - 3.20 - 10.0 -32.0 - 100 mg/L. Three replicates were tested for each test item loading and six replicates for the control. The environmental conditions were within the acceptable limits. The concentrations of test item were analytically verified via analysis of the total organic carbon (TOC) at the start of the exposure and at the end of the exposure. The results of the carbon analysis showed that there was no relationship between the nominal loading levels and the measured TOC values. TOC analysis was carried out to determine the content of the test item in water as a sum parameter. No specific analysis was possible as the test item is a mixture of different compounds. In addition, the observed dose-response relationship was ambiguous as there was no clear relation between concentration and effect. Therefore, no calculation of EL-values was possible. Instead, EL-values were approximated directly from the observation data. All effect values given are based on nominal test item loadings of the test item. The EL50 basic for effect growth rate (72 h) was greater than 100 mg/L. The observed effects did not follow a considered dose-response curve. Therefore, the presented effect levels (especially Ey20) are of low reliability and should be considered with extreme care. The effects may be caused by the presence of undissolved test item in the test medium, since the preparation of the water accomodated fraction did not include a filtration step. Hence, it cannot be excluded that particles of the test item might have caused the observed response.

Based on this result with respect to the growth rate and yield to 2-Propenoic acid, docosyl ester is also considered to be >100 mg/L.

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