Disodium 5-(benzoylamino)-4-hydroxy-3-[[2-(2-methylphenoxy)phenyl]azo]naphthalene-2,7-disulphonate

Endpoint summary

Additional information

Only short-term toxicity studies on three aquatic species are reported, whilst no long-term tests are available.

Fish

The toxicity potential is investigated with three different species (Lepomis macrochirus, Leuciscus idus and Salmo trutta). All tests were performed according to internal methods.

Despite the key study was not carried out according to a OECD Guideline and the test substance purity was ca. 55 %, it has been chosen as a benchmark study for the safety assessment, because it turns out to be the most detailed and complete test among those available.

Healthy bluegill sunfish fingerlings were used as test animals. The percentages of survival were recorded for 5 concentrations and the untreated control. In addition, the main behavioural reactions and their duration, following the dose administration, were recorded.

The reported result is expressed in terms of four - day medium tolerance limit, but in this case it can be compared to a LC50 value, considering that mortality was the discriminating factor in the study.

The TL50 values, reported in the two other studies, were estimated after an observation period of 48h and they are very close to the result of the first test.

Invertebrates

The determination on invertebrates of the substance was investigated through a read across approach, based on the structural similarity of the two main components of target and source substances, on their similar composition and biodegradation potential, because only a short abstract is available for the substance. Nevertheless, the two results are very similar.

The test has been performed according to the guideline 92/69/EEC C.2 on Daphnia magna Straus 1820 for 48 hours.

EC 100 value at 48h was greater than 100 mg/L.

Plants other than algae

The algae are usually preferred as reference aquatic plants in a study of growth inhibition. However, coloured substances cause problems in interpreting test algae, because the effects of the absorption of light can interact with potential toxicity; therefore, the inhibition of the growth of algae would no longer be only the result of a toxic action, but also the result of physical phenomena (shading effect).

The determination on plants of the substance was investigated through a read across approach, based on the structural similarity of the two main components of target and source substances, on their similar composition and biodegradation potential.

The inhibitory effects based on the average specific growth rate and the yield (absolute increase in plant size) to the duckweed Lemna minor was investigated over a period of 7 days.

The test was performed at nominal concentrations of 11.4, 114 and 1140 mg/l of test substance, corresponding to 10, 100 and 1000 mg/l of the active ingredient (AI).

For the endpoint frond number and with respect to growth rate inhibition, the following effects as compared to the untreated controls were observed: 19 % at 100 mg/l and 75 % at 1000 mg/l. No significant effects were observed at 10 mg/l, as determined by Dunnet’s test.

For the endpoint frond number and with respect to yield inhibition, the following effects as compared to the untreated controls were observed: 18 % at 10 mg/l, 41 % at 100 mg/l and 92 % at 1000 mg/l.

Based on these data the median effect concentrations to Lemna minor with respect to growth rate (ErC50) and to yield (EyC50) for the endpoint frond number was estimated to be 100–1000 and about 100 mg/l nominal concentration, respectively.

The no-observed-effect concentrations to Lemna minor with respect to growth rate (NOErC) and yield (NOEyC) for the endpoint frond number were 10 and <10 mg/l nominal concentration, respectively, as determined by Dunnett's test.

For the endpoint dry weight and with respect to growth rate inhibition, the following effects as compared to the untreated controls were observed: 20 % at 100 mg/l and 67 % at 1000 mg/l. No significant effects were observed at 10 mg/l, as determined by Dunnet’s test.

For the endpoint dry weight and with respect to yield inhibition, the following effects as compared to the untreated controls were observed: 22 % at 10 mg/l, 44 % at 100 mg/l and 90 % at 1000 mg/l.

Based on these data the median effect concentrations to Lemna minor with respect to growth rate (ErC50) and to yield (EyC50) for the endpoint dry weight was estimated to be about 100 – 1000 and about 100 mg/l nominal concentration, respectively.

The no-observed-effect concentrations to Lemna minor with respect to growth rate (NOErC) and yield (NOEyC) for the endpoint dry weight were 10 and <10 mg/l nominal concentration, respectively, as determined by Dunnett's test.

Microorganism

The toxicity to microorganism potential is investigated in two studies.

In the key study, the toxicity to activated sludge was determined in a 3-hours respiration inhibition test according to the OECD Guideline No. 209. The test substance concentrations tested were 320, 100, 32 and 10 mg/l. The IC50 value  at 3 h was greater than 320 mg/l.

The second test, although the report is not detailed, confirms the results found previously.

Taking into account these evidences, the LC50/EC50 values found do not justify a classification according to the CLP Regulation (EC 1272/2008).