Dihydrogen hexafluorozirconate(2-)

Endpoint summary

Additional information

Dihydrogen hexafluorozirconate

Substance-specific data are not availabe to evaluate the toxicity of dihydrogen hexafluorozirconate to terrestrial organisms. Since dihydrogen hexafluorozirconate rapidly dissociates into fluoride, hydrogen and zirconium ions upon dissolution in the environment, and only fluoride but not hydrogen and zirconium ions will remain as such in solution, it can be assumed that soil toxicity (if any) will be driven by the fluoride anion. Therefore, full read-across of soil toxicity data of potassium fluoride (CAS #7789-23-3) and other fluorides based upon a molecular weight conversion is justified (see below).

Toxicity data are available for the toxicity of fluoride to soil microbes, plants (monocots only) and invertebrates (arthropods and annelids). The lowest available NOEC for the long-term toxicity (63 days) to NO3-mineralisation (nitrification) amounts to 192.7 mg/kg dihydrogen hexafluorozirconate while the 90-d NOEC for the decrease in biomass of onion (Allium cepa) is 164.5 mg/kg. A NOEC of 1454.4 mg/kg dihydrogen hexafluorozirconate was derived for the long-term (126 days) toxicity to Porcellio scaber and a NOEC of 2181.6 mg/kg for the for the long-term (154 days) toxicity to Eisenia fetida. The lowest available long-term NOEC amounts to 164.5 mg/kg for the growth inhibition of onion and is taken forward to the Chemical Safety Assessment.

Potassium fluoride

Toxicity to soil macro-organisms

The toxicity of various fluoride compounds to Eisenia fetida was investigated over a period of 22 weeks. At higher concentrations sodium fluoride, potassium fluoride and the sodium salt of fluoroacetic acid reduced significantly. Calcium fluoride had no effect. The rate of maturity of the earthworms was also significantly reduced when sodium fluoride and potassium fluoride was used. The number of hatchlings was reduced in the presence of sodium fluoride, while the number of cocoons was reduced in the presence of a low concentration of sodium fluoride and potassium fluoride (Vogel & Ottow, 1992).

Toxicity to terrestrial arthropods

The effects of fluoride concentration were investigated on the numbers of Porcellio scaber in leaf litter. Leaf litter was collected from eight sites at various distances away from an aluminium reduction plant. Results showed that litter collected far from the plant had a lower fibre content, was more sapric and was less acid. Total acid extractable F- in the litter and upper 15 cm of soil was about 41 times as much at the closest site (700 mg/kg) as at the most distant sites (12 and 16 mg/kg). In a bioassay of litter from the study sites, woodlice (Porcellio scaber) had an abnormally high mortality in litter that contained 440 mg/kg or more of acid extractable F-. When F- was added in the form of NaF to the litter, a significant increase in mortality was observed only in treatments exceeding 800 mg/kg (Beyer et al, 1987).

Toxicity to terrestrial plants

On the basis of a large number of fumigation experiments with plants (ornamental crops, fruit crops and conifers) exposed to HF, a relationship was derived between the NOEC and exposure time (all plant species). NOEC values were calculated for highly sensitive, sensitive and slightly sensitive plant species. NOEC values of between 0.2 -7.5 mg/m3 HF are reported for plant species (EU RAR, 2001).

Toxicity to soil micro-organisms

The EU RAR (2001) reports NOEC values from 106 to 3000 mg/kg. The 63 day experiments were carried out in a micro-ecosystem containing poplar litter (30% o.m) and the isopod Porcellio scaber.Nitrification was found to be the most sensitive endpoint investigated in the micro-ecosystem test.