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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

EC50 72h > 100 mg/l
NOEC 72h = 22 mg/l

Key value for chemical safety assessment

EC50 for freshwater algae:
100 mg/L
EC10 or NOEC for freshwater algae:
22 mg/L

Additional information

Several reliable studies are available in order to determine the toxicity of the Stilbene Fluorescent Whitening Agents category to Algae for all substances. In all cases the EC50 recorded was greater than 100 mg/l (see Category Justification Report attached to the section 13 of the dossier).

The substance toxicity to aquatic algae was investigated performing a 72 -hours limit test on the green alga Desmodesmus Subspicatus, following the procedures outlined in the OECD guideline 201. No effects were recorde up to the dose tested of 100 mg/l, thus the EC50 was identified as higher than 100 mg/l (Laus GmbH, 2002).

In further reliable study on the substance to be registered (CAS 16090-02-1), the EC50 value was determined to be 80.59 mg/l (RCC Umweltchemie AG, 1990) and a less reliable study reported that 40 mg/l caused a growth inhibition at 72 hours of 49 % (Novartis Services AG, 1997). 

It is supposed that this result can be traced back to a physical effect, determined by the fluorescent properties of the substance and by the impairment of the enlightenment properties. The solution appears as a turbid suspension and precipitation occurs.

The EU authorities’ agreement refers to the Manual of Decision (EU Manual of Decisions dated July 2006, at http: //ecb. jrc. ec. europa. eu/new-chemicalssection 13.5.3 Alternatives to the algae growth inhibition test with coloured substances) reports that “where it can be demonstrated 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”. Thus, as key study for classification and Risk Assessment has been considered the Algae study performed on a very similar substance, CAS 28950-61-0: the morpholino derivative tetrasulphonated.

The substance is part of the category, as described in the Category Justification Report, part of the same group 2 according to the subcategorisation based on organic functional groups and presents a very high similarity according to Tanimoto distance (> 0.95). It is much more soluble, because of higher sulphonation (380 g/l respect to 2 g/l of CAS 16090-02-1) and it is therefore more environmentally bioavailable. The impurity profile indicated that the levels of inorganic salts and organic impurities are in the same content and impurities have the same estimated toxicological and metabolic profile. This make the analogous substance a conservative representative for environmental toxicity testing, since inorganic impurities described in the substance identification have not a potential toxic effect by themselves, if not based on physical interaction, and read across is therefore justified.