Sodium 4-[(9,10-dihydro-4-hydroxy-9,10-dioxo-1-anthryl)amino]toluene-3-sulphonate

Toxicity to aquatic plants other than algae

Description of key information

The purpose of this test was to evaluate effects of the test item on the growth of the freshwater aquatic plant Lemna gibba (duckweed), according to the OECD 221 guideline and GLP. Both, inhibition of the plant growth based on frond numbers and biomass, in relation to the control cultures, were determined over the test period of seven days. The following treatments were tested: the undiluted filtrate of an equilibrates test item suspension with a loading rate of 100 mg/L and the dilution 1:2.8 1:7.8, 1:22, 1:61. The test media were prepared at the start of the test and at the test medium renewals after two and three days by mixing the test item into test water at a loading rate of 100 mg/L. Intensive stirring for 1 hour was applied to reach a maximum concentration of dissolved test item in test water. After stirring, the suspension was filtered through a 0.45 μm membrane filter. The undiluted filtrate was used as highest test medium and was diluted with test water for preparation of the test media with the lower test concentrations. The preparation of the test medium was based on the OECD Guidance Document on Aquatic Toxicity Testing of Difficult Substances and Mixtures, 2000.

The analytically determined concentrations of the test item in the analyzed test media (the undiluted filtrate and the dilutions 1:2.8 and 1:7.8) at the start of the test medium renewal periods are shown in the table below. At the end of the test medium renewal periods, 77 to 117 % of the initially measured concentrations were found. As the test item was sufficiently stable during the test medium renewal periods of two and three days, the mean measured concentrations were calculated as the arithmetic mean over all measurements per test concentration.

Based on these results, the concentration of 32 mg/L was determined to be the 7-day LOEC as the average growth rate and the yield based on frond numbers after the exposure period of 7 days were statistically significantly lower than in the control and symptoms of toxicity were determined in the lemna at this test concentration. The 7-day NOEC was determined to be 11 mg/L since the growth of the plants (based on frond numbers and dry weight) was not inhibited and no abnormalities in appearance of the plants was observed after the exposure period of 7 days.

The ECx Values for frond numbers and biomass are:

EC10 = 25 mg/L (growth rate; frond numbers) (CI: 18-31)

EC10 = 49 mg/L (growth rate; dry weight) (CI: 31-59)

EC50 > 84 mg/L (growth rate; frond numbers and dry weight)

All the validity criteria were fulfilled according to the OECD guideline 221.

Key value for chemical safety assessment

EC10 or NOEC for freshwater plants:

25 mg/L