Sodium bis[2,4-dihydro-4-[(2-hydroxy-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

E_rC50 (7d) = 12.3 mg/l based on Probit analysis (Gompertz distribution) for frond number

E_rC50 (7d) = 10.1 mg/l based on Probit analysis (Gompertz distribution) for dry weight

Key value for chemical safety assessment

EC50 for freshwater plants:

12.3 mg/L

EC10 or NOEC for freshwater plants:

0.837 mg/L

Additional information

No data on toxicity of Solvent Red 008 to aquatic plants was available, thus the assessment relied on a read across approach. Solvent Red 008 and Similar Substance 02 are chromium complexes with 2 ligands. In both cases, the 2 ligands have the same chemical structure, i.e. a phenyl ring connected via diazo bond to a phenyl pyrazole. These ligands show minor differences in the position of substituents, i.e. hydroxy and nitro groups, as well as in the presence of a sulfonate group in Similar Substance 02.

All information about the read across process is inserted in section 13.

In the available study conducted according to OECD Guideline 221, significant inhibitory effects were determined for all parameters at 3 highest measured concentrations of 1.64, 5.25 and 18.4 mg/l. Upon a 7 -day exposure, effect levels for growth rate (E_rCx) and yield (E_yCx) of frond number and dry weight were estimated. Following results were obtained:

- as for frond number, actual E_yC10 = 0.297 mg/l and actual E_rC10 = 0.837 mg/l

- as for dry weight, actual E_yC10 = 0.591 mg/l and actual E_rC10 = 1.10 mg/l

- as for frond number, actual E_yC50 = 2.54 mg/l and actual E_rC50 = 12.3 mg/l

- as for dry weigth, actual E_yC50 = 3.48 mg/l and actual E_rC50 = 10.1 mg/l.

The test is valid as the doubling time of control frond numbers was calculated to be 37.9 h, corresponding to 1.581 days at day 7. This is less than the maximum allowable doubling time set in OECD guideline 221 (60 h, 2.5 days).