Disodium 3-[[2,2'-dimethyl-4'-[[4-[[(p-tolyl)sulphonyl]oxy]phenyl]azo][1,1'-biphenyl]-4-yl]azo]-4-hydroxynaphthalene-2,7-disulphonate

Toxicity to aquatic plants other than algae

Description of key information

Frond number: ErC50 (7d): 1.347 mg/l as growth rate based on measured concentrations.

ErC10 (7d): 0.366 mg/l as growth rate based on measured concentrations.

Key value for chemical safety assessment

EC50 for freshwater plants:

1.347 mg/L

EC10 or NOEC for freshwater plants:

0.366 mg/L

Additional information

Acid Red 111 was tested for toxicity to Duckweed (Lemna gibba) using 20X AAP medium as dilution water. A preculture was prepared 7 days before the test with healthy colonies with 3 -4 fronds.

Based on 2 preliminary experiments, nominal concentrations of 3.13, 6.25, 12.5, 25.0, 50.0 and 100 mg/l were used in the main study. Measured concentrations deviated more than 20 % from the nominal ones, thus results were based on geometric mean of measured concentrations. As test substance was not stable in test medium, based on the analytical validation, the main test was run as semi-static.

A control group in 6 replicates and 6 concentrations in 3 replicates each were exposed for 7 days; test solution were prepared upon dilution of a stock solution with 20X AAP medium in 400 ml Petri dishes-covered glass beakers filled with 160 ml test solutions. Colonies of plants were added to each vessel: 2 colonies with 4 fornds and 1 colony with 3 fronds. Assessment of growth and morphological changes was done on days 3, 5 and 7.

Main test was run as a semi-static test with renewals on day 3 and 5.

An analytical monitoring was done at start and end of each renewal period, by HPLC method with VIS detection.

For both response variables, i.e. growth rate and yield, NOEC, LOEC and ECx values were determined for both frond number and dry weight.

All validity criteria were met.