Reaction mass of [(2-substituted-4-nitroaryl)diazenyl]methyl(arylamino)-[(2-arylethyl)amino]pyridinecarbonitrile and [(2-substituted-4-nitroaryl)diazenyl]methyl(arylamino)-[(2-arylethyl)amino]pyridine-3-carbonitrile

Toxicity to aquatic algae and cyanobacteria

Description of key information

The 72-hour EC50 for mean algal biomass and for mean growth rate were higher than the loading rate of 100 mg/L. The NOEC was set to 100 mg/L (nominal), both for the tested substance 41'030/A and for its structural analogue FAT 41045.

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 FAT 41'030/A, a structural analogue of FAT 41045, on the growth of the green algal species Scenedesmus subspicatus CHODAT was investigated in a 72-hour static test according to EU Commission Directive 92/69/EEC, C.3, 1992, and the OECD Guideline No. 201, 1984. Both substances are very similar in their chemical structure and, as demonstrated, in a number of physicochemical properties. Therefore, the use of this study for read-across is considered to be appropriate.

 

Due to the low water solubility of the test item, an undiluted filtrate with a loading rate of 100 mg/L was used as the only test medium. A control was tested in parallel. Thus a limit test was performed according to the EU Commission Directive 92/69/EEC to demonstrate that the test item has no toxic effect on the test organisms up to at least this loading rate.

 

At all counting dates, the mean algal cell densities in the test medium were nearly identical or even slightly higher than those in the parallel control cultures. Thus, the test item FAT 41'030/A clearly had no inhibitory effect on the growth ofScenedesmus subspieatus during the exposure period of 72 hours in the undiluted filtrate at a loading rate of 100 mg/L. This loading rate was therefore determined as the 72-hour NOEC (highest concentration tested without toxic effects after a test period of 72 hours). The NOEC might even be higher, but loading rates in excess of 100 mg/L have not been tested, in compliance with the guidelines.

The 72-hour LOEC (lowest concentration tested with toxic effects), and the 72-hour EC₅₀for mean algal biomass and mean growth rate were clearly higher than the loading rate of 100 mg/L. These values could not be quantified, since the test item had no toxic effect on the algae up to the highest test item concentration which could be dissolved in the test water at a loading rate of 100 mg/L.

 

In conclusion, the 72-hour EC₅₀ for mean algal biomass and for mean growth rate were higher than the loading rate of 100 mg/L. The NOEC was set to 100 mg/L (nominal), both for the tested substance 41'030/A and for its structural analogue FAT 41045.