Dipotassium hexafluorozirconate

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

0.163 mg/L

Assessment factor:

10

Extrapolation method:

assessment factor

PNEC freshwater (intermittent releases):

0.107 mg/L

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

0.163 mg/L

Assessment factor:

10

Extrapolation method:

assessment factor

STP

Hazard assessment conclusion:

PNEC STP

PNEC value:

1.77 mg/L

Assessment factor:

10

Extrapolation method:

assessment factor

Sediment (freshwater)

Hazard assessment conclusion:

PNEC sediment (freshwater)

PNEC value:

28.86 mg/kg sediment dw

Assessment factor:

10

Extrapolation method:

assessment factor

Sediment (marine water)

Hazard assessment conclusion:

PNEC sediment (marine water)

PNEC value:

5.77 mg/kg sediment dw

Assessment factor:

50

Extrapolation method:

assessment factor

Hazard for air

Air

Hazard assessment conclusion:

no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:

PNEC soil

PNEC value:

22.5 mg/kg soil dw

Assessment factor:

10

Extrapolation method:

sensitivity distribution

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

no potential for bioaccumulation

Additional information

Dipotassium hexafluorozirconate rapidly dissociates into fluoride, potassium and zirconium ions upon dissolution in the environment. However, zironium ions do not remain in solution, only fluoride ions do. 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.

Indeed, under most environmental conditions, zirconium displays a very low mobility, mainly due to the low solubility of the hydroxide Zr(OH)₄. This limits the concentration of dissolved Zr in most natural solutions (fresh water, seawater as well as soil and sediment porewater) to <0.05 μg/L. Depending on the pH of the environmental medium, different zirconium species exist in solution, including Zr⁴⁺, and various hydroxides. At pH 7, a Zr(OH)₂(CO₃)₂^2-complex may form, but the complex is unstable and Zr(OH)₄forms with decreasing pH. The hydro-bicarbonate (Zr(OH)₄-HCO₃-H₂O) complex may be the most significant Zr complex in natural water (http://www.gtk.fi/publ/foregsatlas, accessed on 12.03.2013). Thus, regarding the environmental toxicity of dipotassium 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.

Substance-specific data are availabe to address the acute toxicity at three throphic levels, i.e. algae, daphnia and fish, while chronic data of dipotassium hexafluorozirconate are only available for algae, the apparently most sensitive trophic level. Chronic toxicity data for invertebrates and fish of potassium fluoride (CAS #7789-23-3) and other fluorides are read-across. Based on available substance-specific aquatic toxicity data and read-across it can be assumed that the aquatic toxicity potential of dipotassium hexafluorozirconate is low and below relevant classification criteria of Directive 67/548 EEC and CLP Regulation (EC) No 1272/2008.

Conclusion on classification

According to Directive 67/548 EEC and CLP Regulation (EC) No 1272/2008, a classification and labelling for aquatic toxicity of dipotassium hexafluorozirconate is not required.