A mixture of: 2,2,6,6-tetramethylpiperidin-4-yl-hexadecanoate; 2,2,6,6-tetramethylpiperidin-4-yl-octadecanoate

Toxicity to aquatic algae and cyanobacteria

Description of key information

NOEC (72h) > 100 mg/L for  green algae species Scenedesmus subspicatus CHODAT [OECD TG 201, EU Method C.3; static]

Key value for chemical safety assessment

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 Commission Directive 92/69/EEC, C.3, 1992, and the OECD Guideline No. 201, 1984.

A limit test was performed in accordance with the directive to demonstrate that the test item has no toxic effect on Scenedesmus subspicatus at a loading rate of 100 mg/L.

Due to the low water solubility of the test item a supersaturated suspension with a loading rate of nominal 100 mg/L was prepared by ultrasonic treatment for 15 minutes. No auxiliary solvent or emulsifier was used. This supersaturated suspension was stirred by a magnetic stirrer at 40°C in the dark over 24 hours to dissolve and disperse a maximum amount of the test item in the suspension. Then the suspension was filtered and the undiluted filtrate was used as the only test concentration. Additionally, a control was tested in parallel.

The mean analytically determined test item concentration in the analyzed test medium samples amounted to 0.15 mg/L at the start of the test. In this test medium, incubated under the test conditions during the test period (but without algae), the measured concentrations of the test substance decreased below the limit of determination of the analytical method of 0.04 mg/L after 72 hours. The losses could be due to hydrolysis of the test item during the performance of the test. The total mean measured concentration (calculated as the average over the mean value at the start of the test and the value for the limit of determination) was about 0.1 mg/L. The biological results are related to the loading rate of 100 mg/L.

The test item had clearly no inhibitory effect on the growth (biomass and growth rate) of Scenedesmus subspicatus during the exposure period of 72 hours at the loading rate of 100 mg/L. Thus, this loading rate was 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 were not tested, according to the guidelines.

The 72-hour LOEC (lowest concentration tested with toxic effects), respectively the 72-hour EC50, EC10 and EC90 for the algal biomass and the growth rate were clearly higher than the loading rate of 100 mg/L. These parameters could not be quantified due to the absence of a toxic effect up to the loading rate of 100 mg/L, and thus above the water solubility limit.