Sodium bis[2,4-dihydro-4-[[2-hydroxy-5-(methylsulphonyl)-4-nitrophenyl]azo]-5-methyl-2-phenyl-3H-pyrazol-3-onato(2-)]chromate(1-)

Toxicity to aquatic plants other than algae

Description of key information

The growth of Lemna gibba exposed to the test item was investigated in a 7 day semi-static test (Institute of industrial organic chemistry, 2017) according to OECD 221 (2006). After 7 days, the ErC50 was determined to be 72.09 mg/L, the ErC10 was determined to be 1.20 mg/L and the NOEC was determined to be 0.59 mg/L. The endpoint values were based on the dry weight determinations and on the time-weighted mean of determined test item concentrations.

Key value for chemical safety assessment

EC50 for freshwater plants:

72.09 mg/L

EC10 or NOEC for freshwater plants:

1.2 mg/L

Additional information

The growth of Lemna gibba exposed to the test item was investigated in a 7 day semi-static test (Institute of industrial organic chemistry, 2017) with daily renewals according to OECD 221 (2006). The definitive test was performed using the following test item concentrations: 150, 50, 16.7, 5.6, 1.9 and 0.62 mg/L plus the control. The test item concentrations were split up into three replicates, the control was split up into six replicates. The test was performed in glass crystallizers containing 150 mL of each treatment per replicate. The highest test item concentration was prepared by mixing an appropriate amount of the test item with deionized water. The test item concentration and the control (deionized water) were mechanically shaken for 72 hours (30 °C, 90 rpm, darkness). After shaking appropriate amounts of 20X AAP stock solutions were added into the test item concentration and the control in order to obtain a stock solution of the test item in 20X AAP medium. The stock solution was visually clear, before the dilution was started. The test item concentrations and the control were left for a settling phase (2h, no shaking, room temperature) before the test organisms were inserted. All test solutions were visually red coloured and clear throughout the exposure period. At the end of the renewal periods precipitation of test substance was observed in the two highest test concentrations, while the 4 lower concentrations were visible as clear red coloured solutions without precipitation of test substance. At exposure termination in the test item concentration 0.62 mg/L no distinctive changes from the development of plants in the control were observed. In the test item concentrations 5.6 and 1.9 mg/L colored roots were observed. In the test item concentration 16.7 mg/L shorter roots, colored fronds and roots were observed. In the test item concentration 50 mg/L colored fronds and roots, shorter roots, smaller fronds and few spots of chlorosis were observed. In the test item concentration 150 mg/L colored fronds and roots, shorter roots, smaller fronds and few spots of necrosis were observed. The nominal test item concentration of 0.62 mg/L was below the LoQ of 1.0 mg/L and consequently all measured values were < LoQ. In fresh samples of higher concentrations the determined test item concentration was in the range of 86.3 – 109.4 % of nominal concentration. Therefore, the test item concentrations were prepared correctly. In spent samples the determined test item concentration was in the range of 90.7 – 29.6 % of nominal concentration in the remaining test item concentrations. The decrease was dependent on the concentration and generally consistent for each concentration with the highest losses in the test concentrations 16.7 and 50.0 mg/L Therefore, the test item concentrations were unstable under the test conditions. A blank control (performed with test solution (20X AAP) without test item) and positive control with the reference substance 3,5-dichlorophenol were tested. After 7 days the ErC50 of 3,5-dichlorophenol was determined to be 9.94 mg/L (based on the frond number). The result was based on the nominal concentration of the reference material. The validity criteria were met. After 7 days, the ErC50 was determined to be 72.09 mg/L, the ErC10 was determined to be 1.20 mg/L and the NOEC was determined to be 0.59 mg/L. The endpoint values were based on the dry weight determinations and on the time-weighted mean of determined test item concentrations.