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Short-term tests with species of three trophic levels are available for Ammonium iron(3+) hexakis(cyano-C)ferrate(4-) (CAS 25869-00-5). It should be noted that all tests (except the OECD 211 study) assessing the aquatic toxicity were conducted with a vehicle since the substance is insoluble in water (< 0.02 mg/L). Algae turned out to be the most sensitive species revealing an EC50 (72 h) of 9.7 mg/L (nominal). However, this concentration is far above the solubility limit of the substance and the effects are most likely related to the increasing blue colour of the test medium leading to absorption of light. Increasingly blue color was observed in the test solutions with increasing concentration of the test substance and a slight amount of blue precipitate was observed at the highest concentration. Therefore, the results are not relevant for the assessment. One short-term study with Daphnia magna resulted in an EC50 (24 h) > 500 mg/L and a NOEC (24 h) of 100 mg/L. Since the study duration was only 24 h and effects were observed a long-term study with aquatic invertebrates according to OECD 211 was conducted. In the main test, a dose-dependent mortality of the adult daphnids was observed (except in the lowest concentration, dilution 1:16). However, these effects are most likely not related to the soluble fraction of the test substance but to physical effects. Therefore, the long-term Daphnia study was repeated with a modified test system. This study resulted in effects on reproduction of D. magna with a NOEC (21 d) of 0.142 mg/L and an EC10 of 0.168 mg/L based on measured concentrations (TWA).

No effects on freshwater fish were observed after 96 h resulting in a LC50 > 100 mg/L (nominal). An additional study investigating the effects on respiration of activated sludge microorganisms according to OECD 209 showed inhibition of respiration > 10% at a nominal concentration of 313 mg/L resulting in a NOEC (3 h) of 100 mg/L. However, the inhibition of the degradation process in sewage treatment plants is not anticipated since the concentration tested is far above the water solubility of the substance.

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