2-[2-[4-(dimethylamino)phenyl]vinyl]-1,3,3-trimethyl-3H-indolium acetate

Toxicity to aquatic plants other than algae

Description of key information

The toxicity of the test substance to Lemna gibba was determined in a study (BASF SE, 99E0476/14X590, 2016) according to the principles of OECD 221 (2006) under GLP conditions. Based on frond number the median concentration causing 50 % inhibition of growth rate of Lemna gibba culture ErC50 after 7 days exposure was determined to be 0.950 mg/L and the ErC10 after 7 days exposure was determined to be 0.038 mg/L.

Key value for chemical safety assessment

EC50 for freshwater plants:

0.95 mg/L

EC10 or NOEC for freshwater plants:

0.038 mg/L

Additional information

The toxicity of the test substance to Lemna gibba was determined in a study (BASF SE, 99E0476/14X590, 2016) according to the principles of OECD 221 (2006) under GLP conditions. The aim of the study was to assess the effects of the test substance on growth rate and yield over a period of 7 days under semi-static conditions with daily renewals. Nine test item concentrations of 10, 3.16, 1.0, 0.316, 0.1, 0.0316, 0.01, 0.00316, 0.001 mg/L (what corresponds to 5.59, 1.77, 0.559, 0.177, 0.0559, 0.0177,0.00559, 0.00177, 0.000559 mg/L of the main ingredient) plus the control were used in the test. The content of the main ingredient in the test item concentrations was determined with a validated spectrophotometric method. Samples of all fresh test item concentrations and the control at exposure initiation and all old test item concentrations and the control at the first renewal were chemically analyzed. The effect concentrations did not exceeding solubility of substance in test medium. In the fresh samples collected at all renewals in the test item concentrations of 10 and 0.1 mg/L the determined content of the main ingredient was in the range of 90.2 – 104.7% of nominal concentration. Therefore, the results confirm correct preparation of the test item concentrations.

In the old samples collected at the first renewal in the test item concentrations of 0.0316, 0.01, 0.00316, 0.001 mg/L the determined content of the main ingredient were below LoD value (LoD = 0.02 mg/L). In the old samples collected at the first renewal in the test item concentrations of 10, 3.16, 1.0, 0.316, and 0.1 mg/L the determined content of the main ingredient was in the range of 104.1 – 108.0 % of nominal concentration. In the old samples collected at all further renewals in the test item concentrations of 10, and 0.1 mg/L the determined content of the main ingredient was in the range of 89.3 – 103.4% of nominal concentration. Therefore, the test item concentrations were stable under test conditions and the effect are expressed in nominal concentrations. In the definitive test, the validity criteria specified in the OECD Guideline No. 221 (2006) were met. Based on the frond number the 7d-ErC50 of the 3,5-dichlorophenol was determined to be 8.26 mg/L, the doubling time of frond number in the control was 1.47 days and the average specific growth rate in the control between day 0 and day 7 was 0.471 d-1 (minimum requirement: higher than 0.275 d-1). Based on frond number the median concentration causing 50 % inhibition of growth rate of Lemna gibba culture ErC50 after 7 days exposure was determined to be 0.950 mg/L and the ErC10 after 7 days exposure was determined to be 0.038 mg/L.