3-Pyridinecarbonitrile, 4-methyl-2,6-bis[(4-methylphenyl)amino]-5-[2-[2-(trifluoromethyl)phenyl]diazenyl]-

Toxicity to aquatic algae and cyanobacteria

Description of key information

The 72-hour NOEC of the test item to Scenedesmus subspicatus was determined to be at least 3.1 µg/L. The 72-hour LOEC (lowest concentration tested with toxic effects) and the 72-hour EC50 for the algal biomass and growth rate were clearly higher than 3.1 µg/L or higher than the loading rate of 100 mg/L. No acute toxic effects occurred within the range of water solubility. Therefore, the test substance is with high probability not harmful to aquatic algae.

Key value for chemical safety assessment

EC50 for freshwater algae:

100 mg/L

EC10 or NOEC for freshwater algae:

100 mg/L

Additional information

The influence of the test item on the growth of the green algal species Scenedesmus subspicatus CHODAT was investigated in a 72-hour static test according to the EU Commission Directive 92/69/EEC, C.3, 1992, and the OECD Guideline No. 201, 1984 (RCC Ltd. 2004c). A limit test was performed in accordance with the EU Commission Directive 92/69/EEC to demonstrate that the test item has no toxic effect on Scenedesmus subspicatus up to the solubility limit of the test item in test water. Due to the low water solubility of the test item, a supersaturated dispersion of the test item with a loading rate of 100 mg/L was continuously stirred at room temperature in the dark over 96 hours. Then, the dispersion was filtered (0.45 µm membrane filter). The undiluted filtrate with the maximum concentration of dissolved test item was used as the test medium. Additionally, a control was tested in parallel. The analytically determined test item concentration in the test medium was 3.2 µg/L at the start of the test and 3.1 µg/L at the end of the test. Consequently, the test item was stable during the test period of 72 hours under the conditions of the test. The mean measured test concentration (calculated as the average over all measurements per test concentration) in the undiluted filtrate was 3.1 µg/L. The reported biological results are based on the mean measured test item concentration as well as on the loading rate. The test item had no inhibitory effect on algal growth during the exposure period of 72 hours in the undiluted filtrate with a loading rate of 100 mg/L (mean measured 3.1 µg/L). The 72-hour NOEC (highest concentration tested without toxic effects after the exposure period of 72 hours) of the test item to Scenedesmus subspicatus was determined to be at least 3.1 µglL. This value might even be higher but higher concentrations could not be tested due to the low water solubility of the test item. The 72-hour LOEC (lowest concentration tested with toxic effects) and the 72-hour EC50 for the algal biomass and growth rate were clearly higher than 3.1 µg/L or higher than the loading rate of 100 mg/L. These values could not be quantified due to the absence of a toxic effect up to the highest test item concentration which could be dissolved in the test water.