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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

The toxicity of the test substance to the freshwater algae Scenedesmus subspicatus was determined in an OECD 201 test with GLP(BASF SE, 2004) After 72 h the ErC10 and ErC50 values were determined to be 0.96 and 2.14 mg/L, respectively. The NOEC for growth rate was 0.65 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:
2.14 mg/L
EC10 or NOEC for freshwater algae:
0.96 mg/L

Additional information

The toxicity of the test substance to the freshwater alga Scenedesmus subspicatus was determined in a test (BASF SE, 2004) according to the principles of OECD 201 (1984) under GLP conditions. 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. This study encompassed 6 treatment groups (5 dose rates of the test item, control). At test start 100 mL of the test concentrations were inoculated with 10000 algal cells per mL test medium and defined volumes of the algal suspensions were sampled after 0, 24, 48 and 72 hours for determination of cell densities by spectrophotometrical measurement. The samples of the test media sampled at the start and at the end of the test after 72 hours of exposure were analyzed via High Pressure Liquid Chromatography (HPLC). The nominal test concentrations of the test substance were 0.25, 0.55, 1.21, 2.662 and 5.856 mg test item/L and a control. The single components of the test substance are not stable in aqueous solution. The ester linkages hydrolyse successively. This led primarily to an accumulation of components with a lower degree of esterification whereas the concentration of the higher substituted components decreased. Therefore the concentration of the test substance seemed to increase in the culture solutions after 24 and 48 hours if the monoester peak was used for evaluation. After 72 hours the hydrolysis of the monoester was almost completed. After 0 hours (test start): The portion of the test substance in % in relation to the concentrations applied initially was determined to be in a range of 100 and 149 % (evaluation for the integration of the monoester peak) and between 32 and 46 % (evaluation by the integration of diester peak). After 72 hours (test end): The portion of the test substance in % in relation to the concentrations applied initially was determined to be in a range of 9 and < 28 % (evaluation for the integration of the monoester peak) and between 6 and 30 % (evaluation by the integration of diester peak). A positive control with the reference substance potassium dichromate was prepared. After 72 hours the Eb10 of the reference substance potassium dichromate was determined to be 0.33 +/- 0.12 mg/L and the EbC50 was determined to be 0.53 +/- 0.20 mg/L. These results indicate the correct sensivity of the test. The results of this study showed, that test substance inhibited significantly the increase of biomass. After 72 h the EbC10 and EbC50 values were 1.1 and 2.4 mg/L, respectively. The NOEC for biomass was 1.21 mg/L. A t-test was performed. At a = 0.05 = 95 % significant level the extinction values of the biomass for each replicate were compared to the values of the control. For the concentrations of 0.25; 0.55 and 1.21 mg/L no significant difference was observed however for the higher substance concentrations from 2.662 mg/L upwards there was a significant difference. There was a significant inhibition of growth rate after 72 hours. The ErC10 and ErC50 values were 1.8 and 4.0 mg/L, respectively. The NOEC for growth rate was 1.21 mg/L. A t-test was performed. At a = 0.05 = 95 % significant level the extinction values of the growth rate for each replicate were compared to the values of the control. For the concentrations of 0.25; 0.55 and 1.21 mg/L no significant difference was observed however for the higher substance concentrations from 2.662 mg/L upwards there was a significant difference. The results of the HPLC showed a decrease of the test substance concentrations during the test, so that the above stated values change based on the actual concentrations of the test substance. Because the NOEC-values were 1.21 mg/L, the analytical results of nominal 0.25 mg/L and 0.55 mg/L were not included. For evaluation all analytical results for the monoester and diester (0 h- to 72 h) for the nominal concentrations of 1.21; 2.662 and 5.856 mg/L were added and the mean value was calculated. The resulting factor of 0.535 was used for multiplication of the already calculated EC- and NOEC-values: After 72 hours the calculated EbC10 and EbC50 values were 0.59 and 1.28 mg/L, respectively. The NOEC for biomass was 0.65 mg/L.The calculated ErC10 and ErC50 values were 0.96 and 2.14 mg/L, respectively. The NOEC for growth rate was 0.65 mg/L.