Sodium 3-[[4-[(2-ethoxy-5-methylphenyl)azo]-1-naphthyl]azo]benzenesulphonate

Endpoint summary

Description of key information

EC50 (48h) in aquatic invertebrates (Daphnia magna) = 8.18 mg/l.

E_rC50 (7d) in aquatic plants (Lemna minor) > 78.4 mg/l, for both frond number and biomass (dry weight)

Additional information

No data on the target substance was available. Therefore, a read across approach was followed, using data on Similar Substance 01.

Further details on the read-across process are reported in section 13.

The target substance is soluble in water, i.e. 7.06 g/l at 20 °C and pH 7.19, and it is not readily biodegradable. The choice of the read-across is further supported by the similar profile of Similar Substance 01, which is not readily biodegradable and has a water solubility of > 1000 g/l at 20 °C.

Detailed description of studies on aquatic invertebrates and plants indicated that:

- test item is not well soluble in daphnia medium, thus test solutions were prepared as water soluble fractions. Separately for each test concentration, appropriate quantities of test item were added to empty glass vessels, daphnia medium was added and these mixtures were moderately stirred overnight, followed by filtration.

- minimal to major precipitation at nominal concentration of 31.6 and 100 mg/l a.i. in lemna medium occurred.

Thus, effect levels were reported as measured concentrations.

Aquatic invertebrates

The acute toxicity to Daphnia magna was determined in a 48-hour static test, according to OECD guideline 202. As test substance was only partially soluble in test medium, test solutions were prepared as water soluble fractions. During the 48 -h test period, concentrations were measured by HPLC at 0 h, 24 h and 48 h and proved to be satisfactorily maintained. Geometric mean of measured concentrations were: 1.85, 3.37, 5.95, 12.0 and 42.1 mg/l a.i., varying between 97 and 101 % of initial value of soluble fraction. After a 48 -hour exposure, based on measured concentrations of active ingredient., a NOEC of 3.37 mg/l (i.e. highest concentration at which less than 10 % immobilisation was seen) and an EC50 of 8.18 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 57 to 71 % of the initial value after 7 days. 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, significant effects in terms of growth rate of frond number and dry weight (i.e. > 10 % inhibition comapred to controls) were only evident at the highest tested concentration of 78.4 mg/l, as measured content of a.i.. In particular, growth rate of frond number and dry weight showed 18 % and 16 % inhibition, respectively. On these bases, 50 % effect levels were reasonably estimated to be > 100 mg/l a.i..

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 EC50 (48 h) for daphnia and EC50 (72 - 96 h) for algae or aquatic plants.

Toxicity on daphnia was assessed in a 48-hour study and acute immobilisation was seen in 50 % of daphnia exposed at concentration of 8.18 mg/l.

Toxicity on lemna was assessed in 7-day test and effects on growth rate of fronds and dry weight were with E_rC50 > 100 mg/l.

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 results obtained with daphnia, relying on a read across approach, a classification for chronic aquatic toxicity was applied to Acid Orange 116 in cat. 2 (H411) according to the CLP Regulation (EC 1272/2008).