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

Endpoint summary

Description of key information

Short-term toxicity to fish: LC50 (96h) = 3.7 mg/l

Short-term toxicity to invertebrates: EC50 (48h) 24.1 mg/l

Toxicity to aquatic plants: E_rC50 (7d)= 12.3 mg/l referred to frond number; E_yC50 (7d) = 10.1 mg/l referred to dry weight

Additional information

No data on Solvent Red 122 was available. Therefore, a read across approach was followed, using data on Similar Substance 02, as detailed in section 13.

Solvent Red 122 (acid) and Similar Substance 02 (sodium salt) 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.

Due to the sulfonate group and the salification, Similar Substance 02 has a solubility in water of ca. 135 g/l compared to Solvent Red 122, which is practically insoluble. In addition, Similar Substance 02 has higher partition coefficient than Solvent Red 122. For both sustances, no ready biodegration potential is expected.

Overall, the adopted read across was considered as acceptable and consistent with a precautionary perspective. Indeed, based on solubility in water and partition coeffiecient, the read across substance was expected to be more bioavailable to aquatic species and to more likely cross biological membranes compared to Solvent Red 122. Upon absorption, similar toxic potential is expected based on the structural similarity.

Available studies on Similar Substance 02 investigated toxicity to fish, aquatic invertebrates and aquatic plants other than algae. Detailed description of studies did not indicate any sign of precipitation. Thus, the decrease in measured concentrations in the study on aquatic plants with respect to nominal, i.e. 65 - 92 % of nominal, was possibly due to absorption and/or degradation processes.

Fish

The study on fish followed OECD guideline 203, identifying a LC50 of 3.7 mg/l and a NOEC of 2.07 mg/l for mortality at 96 hours. No sublethal effects were reported up to a concetration of 0.939 mg/l. There was evidence that concentrations were satisfactorily maintained throughout the test.

Aquatic invertebrates

The acute toxicity to Daphnia magna was determined in a 48 -hour static test, according to OECD guideline 202. During the test, measured concentrations of test substance were within 95 - 96 % of the nominal values. Therefore, the test substance resulted as stable under test conditions. After a 48 -hour exposure, a NOEC of 9.39 mg/l and an estimated EC50 of 24.1 mg/l were determined.

Aquatic plants

The toxicity to Lemna minor was determined in a 7-day static test, according to OECD guideline 221. During the test, measured concentration decreased and became 92 to 65 % of the initial value after 7 days, for concentrations above the LOQ of the analytical method. Geometric means of measured concentrations were used in the assessement. Effect concentrations were determined in terms of inhibition of growth rate and yield of both frond number and dry weight. After a 7-day exposure, estimated E_rC50 = 12.3 mg/l for frond number and E_rC50 = 10.1 mg/l for dry weight were determined.

Justification for classification or non-classification

According to the CLP Regulation (EC 1272/2008), the threshold of classification of a substance for acute aquatic toxicity is 1 mg/l. This limit is compared with LC50 (96h) for fish, EC50 (48 h) for daphnia and EC50 (72 - 96 h) for algae or aquatic plants.

The classification process relied on data on fish, aquatic invertebrates and aquatic plants.

Toxicity to fish was assessed in a 96 -hour study and resulted in acute mortality in 50 % of fish exposed at concentration of 3.7 mg/l.

Toxicity on daphnia was assessed in a 48-hour study and acute immobilisation was seen in 50 % of daphnia exposed at concentration of 24.1 mg/l.

Toxicity on lemna was assessed in 7-day test and effects on growth rate of fronds and dry weight were reported with E_rC50 = 12.3 mg/l and E_rC50 = 10.1 mg/l, respectively.

No chronic toxicity data is available from long-term studies. In case of lack of chronic data, the potential for chronic toxicity is identified by appropriate combinations of acute toxicity data and lack of biodegradability. The threshold of classification is 100 mg/l.

Based on the results obtained with fish, classification for chronic aquatic toxicity in cat. 2 (H411) was applied according to the CLP Regulation (EC 1272/2008).