3,3'-[(4-{(E)-[2-bromo-4-nitro-6-(trifluoromethyl)phenyl]diazenyl}phenyl)imino]dipropanenitrile

Toxicity to aquatic algae and cyanobacteria

Description of key information

The 72-hour EC50 for the mean algal biomass and the mean growth rate were higher than 209 µg/l (nominal: 100 mg/l). This concentration was also defined as NOEC in this test.

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 41'029/A on the growth of the green algal species Scenedesmus subspicatus CHODAT was investigated in a 72-hour static test according to the Commission Directive 92/69/EEC, C.3,1992, and the OECD Guideline No. 201,1984.

Due to the low water solubility of the test item, a supersaturated dispersion of the test item with a loading rate of nominal 100 mg/l was continuously stirred at room temperature in the dark over 3 hours. Then the dispersion was filtered. No longer stirring period than 3 hours was chosen because a significant loss of the test item was analytically determined in filtrates after periods of 24 and 96 hours, probably by precipitation of the test item. The undiluted filtrate with the maximum concentration of dissolved respectively very finely dispersed test item was used as the only test medium. Additionally, a control was tested in parallel. Thus a limit test was performed according to the Commission Directive 92/69/EEC.

The analytically determined test item concentration in the analyzed test medium samples amounted to 222 µg/l at the start of the test. At the end of the test, 195 µg/l were measured. Under the test conditions, the test item was sufficiently stable during the test period of 72 hours. Therefore, all biological results are related to the mean measured test item concentration of 209 µg/l (calculated as the average over all measurements in the undiluted filtrate).

The test item FAT 41'029/A had clearly no inhibitory effect on the growth (biomass and growth rate) of Scenedesmus subspicatus during the exposure period of 72 hours at the mean measured concentration of 209 µg/l. This test concentration 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 concentrations in excess of 209 µg/l could not be tested due to the low water solubility of the test item. The 72-hour LOEC (lowest concentration tested with toxic effects), respectively the 72-hour EC50 for the mean algal biomass and the mean growth rate were clearly higher than 209 µg/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 that could be dissolved or very finely dispersed in the test water at a loading rate of 100 mg/l. At the microscopic examination of the algal cells after the 72 hours test period, no difference was observed between algae growing at the loading rate of nominal 100 mg/l (mean measured concentration 209 µg/l) and algae growing in the control.

In conclusion, FAT 41'029/A had no toxic effect on the green algae Scenedesmus subspicatus up to its water solubility limit.