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Sediment toxicity

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Since dipotassium hexafluorotitanate rapidly dissociates into fluoride, potassium and titanium ions upon dissolution in the environment, and only fluoride but not titanium ions will remain in solution, it can be assumed that toxicity (if any) will be driven by the fluoride anion. Therefore, the lowest EC25 of 290.2 mg F/kg derived for the 28-d growth of Hyalella azteca is read-across to dipotassium hexafluorotitanate resulting in an EC25 of 611.2 mg/kg dw and is taken forward to the chemical safety assessment. 

Key value for chemical safety assessment

Additional information

Since dipotassium hexafluorotitanate rapidly dissociates into fluoride, potassium and titanium ions upon dissolution in the environment, and only fluoride but not titanium ions will remain in solution, it can be assumed that toxicity (if any) will be driven by the fluoride anion. Therefore, full read-across of sediment toxicity data of fluoride based upon a molecular weight conversion is justified. Due to the electronegativity of the flouride ion, little partition to the sediment can be assumed. It follows that sediment is unlikely to become contaminated and, in turn, this means that the contamination of sediment systems is unlikely. Regarding the toxicity of fluoride in respective long-term (10 – 28 d) growth and survival tests in sediment spiked with sodium fluoride, Hyalella azteca was the most sensitive species for growth (EC25 = 290.2 mg F/kg), followed by Chironomus tentans (EC25 = 661.4 mg F/kg), Hexagenia limbata (EC25 = 1221.3 mg F/kg), and Pimephales promelas (EC25 = >5600 mg F/kg). Hyalella azteca was also the most sensitive species for survival (LC50 = 1114.6 mg F/kg), followed by Hexagenia limbata (LC50 = 1652.2 mg F/kg) and Pimephales promelas and Chironomus tentans (LC50 > 5600 mg F/kg for both). Thus, long-term toxicity data are available for 4 species, including a mayfly, a midge, and an amphipod. The lowest EC25 of 290.2 mg F/kg derived for the 28-d growth of Hyalella azteca is read-across to dipotassium hexafluorotitanate resulting in an EC25 of 611.2 mg/kg and taken forward to the chemical safety assessment.