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Toxicity to microorganisms

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Description of key information

EC50 (3h) > 1000 mg/l
NOEC (3h) ≥ 1000 mg/l

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:
1 000 mg/L

Additional information

There are no experimental data available on the Leucophor 1111X, thus a read across approach with the structural analogous Stilbene derivatives Fluorescent Whitening Agents has been proposed.

The inhibitory effect of analogous substance 01 on the respiration rate of aerobic wastewater microorganisms of activated sludge was investigated in a 3-hour respiration inhibition test according to the OECD Guideline 209. A limit test was performed with one concentration of the substance of nominal 1000 mg/l, to demonstrate that the test item has no toxic effect on activated sludge microorganisms up to and including this concentration. The test item had no significant inhibitory effect (<15 %) on the respiration rate of activated sludge after the incubation period of three hours at the limit test concentration of 1000 mg/l. Thus, the 3-hour NOEC (EC15) of the test item to activated sludge microorganisms is equal/higher 1000 mg/l (Grützner, 2005).

Further data on structural analogous substances are available and they confirm that the Stilbene Fluorescent Whitening Agents investigated are not toxic to microorganisms.

All the substances used in a read across approach are Stilbene derivatives Fluorescent Whitening Agents salts. They display similar structural and physicochemical properties: all of them exhibit high degree of dissociation in water and very low octanol/water partition coefficients because to a higher affinity with water phase than the octanol one. They are all very soluble in water, due to the presence of sulphonated groups in the molecules; all of them are non readily biodegradable and are expected to undergo to the same environmental fate.

In both cases the read across approach can be considered as reliable and representative; the differences occurring in the structure formulas (i.e. substituents) are expected to not significantly impact the toxicity to microorganisms.

Further details about the justification for read across approach are given in the report attached to the Section 13 of this dossier.