Disodium 4,4'-bis[[6-anilino-4-[(2-hydroxyethyl)methylamino]-1,3,5-triazin-2-yl]amino]stilbene-2,2'-disulphonate

Short-term toxicity to fish

Description of key information

LC50 (96 h) Zebra fish > 100 mg/l

Key value for chemical safety assessment

LC50 for freshwater fish:

100 mg/L

Additional information

The short-term toxicity to fish was tested on CAS 13863-31-5 in one reliable study (Bionomics Inc., 1971) with EC50 greater than 85 mg/l, but no analytical concentrations measures were performed. Based on the described physicochemical properties it can be expected that the substance is stable in the testing environment, therefore it is assumed that the nominal concentration will correspond to the measured.

Furthermore, two summaries are available: both describe a test performed at 48 h on trout. In one case the LC50 was stated at 140 mg/l (Ciba-Geigy Ltd. 1978 and Ciba-Geigy Ltd., 1979), while in the second one the LC50 was stated at 45 mg/l (Ciba-Geigy Ltd. 1975 and Ciba-Geigy Ltd., 1989). Test procedures are scientifically acceptable, nevertheless many detail are missing; furthermore there are no evidence that the concentration of the substance being tested has been satisfactorily maintained throughout the test.

 

In general the studies performed on the substance under registration present some deficiencies, therefore studies performed on similar substances belonging to the category of Stilbene Fluorescent Whitening Agents, group 3, have been taken as main reference.

The tested substances CAS 4193-55-9, CAS 70942-01-7 and CAS 16470-24-9 are the dihydroxyethylamino derivatives disulphonated sodium salt, the dihydroxyethylamino derivatives sodium/potassium salt and the dihydroxyethylamino derivatives tetrasulphonated, respectively. In the case of the CAS 70942-01-7 the presence of potassium ion has no relevant toxicological influence for the endpoint.

For all the analogous water solubility is higher than for the substance under registration (CAS 13863-31-5), therefore they are more bioavailable in the water compartment and can be considered as conservative examples.

The chemical structures are very similar, with Tanimoto similarity higher than 95 %: the CAS 13863-31-5 has a methyl group where the analogues has a hydroxyethyl substituent on the nitrogen atom. Based on the OECD Toolbox modelling of the liver metabolisation, both structures share the same monohyroxy derivative as main metabolite. Biological reactivity for the substance under registration is therefore not expected higher that the considered analogues substances.

All analogues tested showed a LC50 > 100 mg/l on fish at 96h.

A further prolonged semistatic assay over 14 days was conducted with Brachydanio rerio on CAS 16470-24-9. Endpoints were mortality, signs of intoxication, length and weight. The nominal concentrations were 100, 316 and 1000 mg/l. There was no mortality and no difference in body weight at nominal concentrations of 100 and 316 mg/l. Only at 316 mg/l one fish showed slackening in movement (Bayer AG., 1992).

Two fish acute toxicity tests are available (Ciba-Geigy, 1994 and 1998) on CAS 16090-02-1 pre-treated with light in order to obtain a high percentage of photodegraded products and verify their impact on aquatic toxicity. Both tests resulted in a LC50 > 100 mg/l, demonstrating that those degradation products are no more dangerous for the environment than the parent compounds.

As a conclusion, based on the most reliable studies, the tested substance and the photodegradation products related are considered as not acutely harmful to fish, with LC50 96h > 100 mg/l.