Disodium hydrogen bis[3-hydroxy-4-[(2-hydroxy-1-naphthyl)azo]naphthalene-1-sulphonato(3-)]chromate(3-)

Endpoint summary

Additional information

Three acute tests on the three trophic levels are available, specifically acute fish toxicity on Acid Blue 193 and invertebrates and aquatic plants acute toxicity on the analogue substance.

At the experimental conditions the target substance shows toxicity for fish with an EC50,96h equal to 22 mg/l.

The study on algae was not performed while a study with Lemna Minor was conducted for assessing the toxicity of the dye to aquatic plants. In fact, several studies on algae conducted on dark dyes, including those with a modified test system for dye-stuffs, showed that the growth inhibition is not due to a real toxic effect of the dye, but due to the light absorption of the stained water. Modified test system is usually conducted with the dye above the algae testing solution, in a different vessel and not into contact with the alga. The same toxicity expressed as grow rate and yield inhibition observed when tha algae is in contact with the dye was observed in the modified test showing that toxicity was related to the shading effect of the dye. However, this modification impy only the assessment of the shadowing effect without testing the real toxic potential of tested substance for algae.

Lemna minor is an aquatic plant that develops his leaves on the surface of the water, while nourishing substances are taken from the water solution. By means of this aquatic plant, the observed effect is only related to the potential toxicity of the substance and not to the potential shading effect of a classical Alga study.

The use of Lemna Minor as testing system is also justified based on the Manual of Decision (EU Manual of Decisions dated July 2006, athttp://ecb.jrc.ec.europa.eu/new-chemicalssection 13.5.3 Alternatives to the algae growth inhibition test with coloured substances.)“where it can be demonstrated in the case of highly coloured substances that algal growth is inhibited solely as a result of a reduction in light intensity, then the 72h EC50 for algae should not be used as a basis for classification.” In order to make a distinction between shading and toxic inhibition effects, in 1994 some modifications to the algae growth inhibition test, known as the ETAD (Ecological and Toxicological Association of Dyes and Organic Pigments Manufacturers) method (also known as the double flask method), were suggested. Advanced insights revealed that the ETAD method is too simplistic to allow evaluation of both toxic and light absorption effects of the coloured substances and should not be used any more.

For highly light absorbing substances, the modified standard algae growth inhibition test is not recommended. With these particular substances, a modified standard Lemna-test (draft OECD guideline 221) is recommended.  

The toxicity to aquatic plants was therefore tested following OECD 221 showing some inhibition to the grow rate with ErdwC50 equal to 73.8 mg/l.

The same potential toxicity was determined in the short term toxicity to invertebrates, specifically Daphnia Magna, were the EC50, 48h is equal to 30.2 mg/l.

The test on fish toxicity being the most conservative and performed on the actual substance was used for classification of the substance and PNEC calculations.