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Long-term toxicity to aquatic invertebrates

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Description of key information

No toxic effects could be recorded in the range of solubility. 

Key value for chemical safety assessment

Additional information

An study following OECD guideline 211 under consideration of GLP was conducted with nominal test concentration of 0, 0.46, 1, 2.2, 4.6 and 10 mg/L.The analytically determined water solubility in the test media is clearly below 1 mg/L (cf. Table 1 below).Thus, the 10 mg/L concentration group clearly exceeded the water solubility in the test medium. A stock solution of 10 mg/L was used to prepare the lower concentrations by serial dilution. No effects could be observed in the lower concentration groups (0.46, 1, 2.2, 4.6 mg/L), however, the highest concentration of 10 mg/L had a minor effect on Daphnia reproduction after 21 days of exposure (13 %). It is assumed, the observed effect is due to better soluble impurities present in the test substance rather than the pigment itself, which is expected to be not toxic. The impurities listed in the certificate of analysis of the batch used for the study are all well below 1% and therefore not relevant for classification purposes. However, some of them are known to have toxic effects on aquatic organisms and the observed effects in the highest concentration group are expected to be caused by these better soluble impurities.To clarify this aspect, it was decided to conduct a second experiment using a saturated solution of the test substance prepared at a loading rate of 1 mg/L. This loading rate still clearly exceeds the water solubility in the test medium, thus, it can be guaranteed that the additional study was conducted at the highest concentration of test substance possible. Furthermore, the loading rate of only 1 mg/L lowers the amount of better soluble impurities in the test medium by a factor of 10 and therefore allows a clearer statement of the toxic potential of the pigment itself. At this loading rate, no effects could be observed which is regarded as clear proof, that the observed effects at 10 mg/L in the first experiment are caused by better soluble impurities and therefore, the pigment itself is not toxic to aquatic invertebrates.

In conclusion, the substance is with high probability not toxic to aquatic invertebrates.

Table 1: A non-GLP study on the water solubility in the different test media revealed the following solubilities.

Medium Concentration [µg/L]
M4 105
M4 w/ Daphnia and algae 87
M4 w/o Daphnia and algae 86
mixed water * 273
OECD medium 303

* Non chlorinated charcoal filtered tap water, mixed with deionized water

The nominal concentration of 1 mg/L used for the second experiment was therefore clearly above the maximum water solubility in the test medium. Thus, it can be guaranteed that the Daphnia were exposed to a saturated solution of the test compound.