disodium [N, 2-[(2-hydroxy-5-nitrophenyl)azo]-3-oxobutyramidato(2-)][3-hydroxy-4-[(2-hydroxy-1-naphthyl)azo]-7-nitronaphthalene-1-sulphonato(3-)]chromate(2-)

Endpoint summary

Description of key information

Short-term toxicity to aquatic invertebrates

EC50 = 2.3 mg/l

Toxicity to aquatic plants other than algae

ECr50 = 192 mg/l based on frond number and on dry weight

Additional information

No studies on "Aquatic toxicity" are available for the substance in itself.

Nevertheless studies conducted with analogue molecules (Similar Substance 01 and Similar Substance 03) were considered in order to complete the assessment. Further information are reported in the Read Across justification attached to section 13.

Short-term toxicity to aquatic invertebrates

To determine the short-term toxicity to aquatic invertebrates, the substance (Similar Substance 01) under registration was tested on Daphnia sp. according to OECD Guideline 202. The concentrations tested were: 1.5/0.3/0.9/3.4/8.2/4.4/4.7/11.4/28.2 mg test article /l based on analytical results. The nominal concentrations were 1.0/1.8/3.2/5.8/10/18/32/58 and 100 mg test article /l.

The EC50 was determined in two ways: graphically, interpolating the point plotted on a graph; and statistically, calculating with the "probit model" method. The EC50 at 48 hours were 1.6 and 2.3 mg/l respectively. The EC50 value obtained statistically has been used as reference due to the more reliability of the method.

EC50 = 2.3 mg/l

Toxicity to aquatic plants other than algae

The inhibitory effects of the test substance (Similar Substance 03) to the duckweed Lemna minor were investigated over a period of 7 days, based on the frond number and biomass (dry weight), following the guideline OECD 221.

The test solutions were prepared by respective dilutions of a stock solution in SIS Medium. The test was performed at 230, 72.8, 23.0, 7.28 and 2.30 mg/l nominal concentration, corresponding to 150, 47.4, 15.0, 4.74, 1.50, and 0.474 mg/l of the active ingredient.

Three parallel test vessels were used for each test concentration of the test item and six vessels for the blank controls.

The test concentrations during the 7 day test period were determined by photometry at the beginning of the test, as well as after 3, 5 and 7 days of exposure. These analyses confirmed the right dosage of the test item, and showed that the concentrations of the test item remained stable over the whole 7 day test period. However, the lowest concentrations did not remain in the 80-120 % range of the nominal concentration. Therefore, the effective concentrations (ErCx and EyCx) were assessed based on the geometric mean (GM) of the measured concentrations of the active ingredient.

The two endpoints frond number and biomass (dry weight) were investigated at days 3, 5 and 7, and each of them were assessed as growth rate and yield.

The ERx50 values based on growth rate were:

ECr50 = 192 mg/l based on frond number

ECr50 = 192 mg/l based on dry weight

Justification for classification or non-classification

According to the CLP Regulation (EC n. 1272/2008), Part 4: Environmental Hazards, the substances can be classified for hazardous to the aquatic environment when the following criteria are met:

A )Acute (short-term) aquatic hazard

Category Acute 1: 96 hr LC 50 (for fish) and/or 48 hr EC 50 (for crustacea) and/or 72 or 96 hr ErC 50 (for algae or other aquatic plants) ≤ 1 mg/l

B) Long-term aquatic hazard

(iii) Substances for which adequate chronic toxicity data are not availableand the substance is not rapidly degradable and/or the experimentally determined BCF ≥ 500 (or, if absent, the log K ow ≥ 4).

Category Chronic 1:96 hr LC 50 (for fish) and/or 48 hr EC 50 (for crustacea) and/or 72 or 96 hr ErC 50 (for algae or other aquatic plants) ≤ 1 mg/l

Category Chronic 2: 96 hr LC 50 (for fish) and/or 48 hr EC 50 (for crustacea) and/or 72 or 96 hr ErC 50 (for algae or other aquatic plants)> 1 to ≤10 mg/l

Category Chronic 3:96 hr LC 50 (for fish) and/or 48 hr EC 50 (for crustacea) and/or 72 or 96 hr ErC 50 (for algae or other aquatic plants) > 10 to ≤ 100 mg/l

Based on the above results, the Daphnia study provides the lowest toxicity endpoint and therefore will be used for Classification as Aquatic Chronic 2 (H411).