Disodium [N-(2-chlorophenyl)-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 fish

LC50 = 2 mg/l

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

Short-term toxicity to fish

The assessment of short-term toxicity to fish of the substance under registration is based on two studies.

The key study (Huntsman, 1981) was conducted on zebrafish following a procedure similar to OECD 203. The purity of the substance was 56.78 %. The tested concentrations were: 1.0/3.0/10.0/30.0/100.0 mg/l. The LC50 after 96 hours of exposure was 2 mg/l.

The supporting study (Huntsman, 1984) was performed with a lower purity of test article, 28%. The procedure was similar to OECD 203 guideline and the test system was zebrafish. The following concentrations of substance were tested: 1.0/3.0/10.0/30.0 mg/l. The LC50 calculated was 4 mg/l.

The two studies were performed according to similar procedures and using the same test substance; the results were similar but in the key study was used a test article with higher purity than the one used in the supporting study. The LC50 obtained in the key study, 2 mg/l, is little lower and more precautionary than the LC50 obtained in the supporting study, 4 mg/l.

Short-term toxicity to aquatic invertebrates

To determine the short-term toxicity to aquatic invertebrates, the substance 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.

Toxicity to aquatic plants other than algae

No studies on the "toxicity to aquatic plants other than algae" are available for the substance in itself.

Nevertheless a study have been conducted with an analogue molecule (Similar Substance 02) in order to complete the assessment. Further information are reported in the Read Across justification attached to section 13.

The inhibitory effects of the test substance 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 Fish toxicity study provides the lowest toxicity endpoint and therefore will be used for Classification (Aquatic Chronic 2).