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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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Dihydrogen hexafluorozirconate will rapidly dissociate into fluoride, hydrogen and zirconium ions upon dissolution in the environment. However, zironium and hydrogen ions will not remain as such in solution, only fluoride ions do. Therefore, full read-across to potassium fluoride (CAS #7789-23-3) and other fluorides based upon a molecular weight conversion is justified. Fluoride accumulates in aquatic organisms predominantly in the exoskeleton of crustacea and in the skeleton of fish; no accumulation was reported for edible tissue. Accordingly, it can be assumed that dihydrogen hexafluorozirconate does not have a potential for bioaccumulation in aquatic tissues.

Key value for chemical safety assessment

Additional information

Dihydrogen hexafluorozirconate

Dihydrogen hexafluorozirconate will rapidly dissociate into fluoride, hydrogen and zirconium ions upon dissolution in the environment. However, zironium and hydrogen ions will not remain as such in solution, only fluoride ions do. The hydrogen ion attaches to a hydroxide ion to form a water molecule. The analysis of dissolved zirconium levels in aquatic toxicity test solutions for algae, daphnia and fish according to OECD 201, 202 and 203 (Schlechtriem, 2013a, b; Teigeler, 2013) indicates that up to a loading of 10 mg/L dipotassium hexafluorozirconate, very low levels of zirconium remain in solution at environmentally relevant pH (< 10%) while more than 75 % of the fluoride could be recovered.

Thus, regarding the environmental fate and toxicity of dihydrogen hexafluorozirconate, it can be assumed that toxicity (if any) will be driven by the fluoride anion. Therefore, full read-across to potassium fluoride (CAS #7789-23-3) and other fluorides based upon a molecular weight conversion is justified.

Potassium fluoride

In freshwater aquatic organisms it was found that the fluoride accumulates primarily in the exoskeleton of crustacea and in the bones of fish. In fish, the BCF value was between 53 -58 (d.w.) and <2 (w.w.). In crustacea, BCF value was <1 (d.w.). The highest reported BCF value for mollusca and aquatic macrophyta were 3.2 and 7.5 (w.w) respectively. In an experimental marine ecosystem with fish, crustaceans and plants, fluoride was found to accumulate in all species. The highest value, 149, was found in fish. BCF values for crustacea range from 27 to 62. Fluoride concentrations up to 30 mg F/kg were found in consumption fish. The limited data indicate that fluoride biomagnification in the aquatic environment is of little significance. Fluoride accumulates in aquatic organisms predominantly in the exoskeleton of crustacea and in the skeleton of fish; no accumulation was reported for edible tissue.

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