Reaction mass of 3,3'-(1E,1'E)-(4,4'-(6-(bis(2-hydroxyethyl)amino)-1,3,5-triazine-2,4-diyl)bis(azanediyl)bis(3-methoxy-4,1-phenylene))bis(diazene-2,1-diyl)dibenzenesulfonic acid and disodium 3,3'-[[6-[bis(2-hydroxyethyl)amino]-1,3,5-triazine-2,4-diyl]bis[imino(3-methoxy-4,1-phenylene)azo]]bis[benzenesulphonate]

Toxicity to aquatic plants other than algae

Description of key information

An OCED 221 study was carried out to determine the effects of the tested substance on the growth of the freshwater aquatic plant Lemna minor. After 7 days of exposure an EC50 value of > 100 mg/L (front number/biomass, growth rate), an EC10 value of 6.55 mg/L (front number, growth rate), an EC10 value of 1.01 mg/L (biomass, growth rate) and an a NOEC of 7.3 (frond number, growth rate) were determined.

Key value for chemical safety assessment

EC50 for freshwater plants:

100 mg/L

EC10 or NOEC for freshwater plants:

1.01 mg/L

Additional information

EC50 "> 100 mg/L"; EC50 and NOEC refer to biomass, growth rate

A growth inhibition test with the freshwater aquatic plant Lemna minor was conducted according to OECD 221 (March 2006) in order to investigate the aquatic phytotoxic effect of the tested substance. Lemna minor is a model organism for aquatic fresh water plants.

The aim of the study was to determine the effects of the tested substance on the growth of the freshwater aquatic plant Lemna minor. To achieve this, a series of test item concentrations in aqueous solutions was prepared (nominal 4.95, 10.9, 24.0, 52.7, 116 mg/L) and the plants were allowed to grow in these concentrations, as well as in controls without the test item, for a test period of 7 days under controlled conditions (temperature, illumination).

The data obtained were analysed using a regression model in order to estimate the concentration that would cause a x% growth inhibition, i.e. ECx (e.g. EC50, EC20 or EC10). As additional endpoints the No Observed Effect Concentration (NOEC) and Lowest Observed Effect Concentration (LOEC) will be reported if relevant.

Samples from the test solutions were analysed to determine actual levels of the test item at start of exposure period (time 0 days) and following 7 days of exposure. At time 0 days the measured concentrations range between 97–102 % and decrease after 7 days exposure at between 40–100 % of the nominal concentrations. Therefore, the test item concentration based on nominal concentration was not stable as it declined more than 20% throughout the exposure period.

All concentration levels were measured, and the biological results are additionally calculated and reported based on geometric mean measured concentrations at each concentration level.

A clear concentration-response relationship was observed for both biological parameters frond number and biomass evaluating growth rate and yield during the exposure period. According to the guideline OECD 221 and REACH Guidance R.7b (2017) front number is the primary measurement variable. For the measured variable 'front number growth rate' the endpoints EC50 >100 mg/L, EC10 6.55 mg/L and NOEC 7.3 mg/L were obtained based on geometric mean measured concentrations.

For the measured variable biomass growth rate the endpoints EC50 >100 mg /L, EC10 1.01 mg /L and NOEC < 2.73 mg /L were obtained based on geometric mean measured concentrations.

All validity criteria are met.This toxicity study is classified as acceptable and satisfies the guideline requirements for the growth inhibition test with Lemna minor.