Ammonium tetrafluoroborate

Short-term toxicity to fish

Administrative data

Endpoint:

short-term toxicity to fish

Data waiving:

study technically not feasible

Justification for data waiving:

the study does not need to be conducted because the substance is unlikely to cross biological membranes, hence indicating that aquatic toxicity is unlikely to occur

Justification for type of information:

Ammonium tetrafluoroborate is a non-polar salt molecule, of two different ionic parts: NH4 as the cation and BF4 as the anion. It is water soluble and is easily hydrolysed, hence, not likely to pass the biological membrane of fish as ammonium tetrafluoroborate. The ammonium ions are themselves a waste product of the metabolism of animals. In fish and aquatic invertebrates, it is excreted directly into the water. Even the BF4 cation is being hydrolysed in water at room temperature. Research has proven that the toxicity of ionic liquids come from the length of the alkyl chains. Ammonium tetrafluoroborate is an ionic liquid, but it does not contain any alkyl chains on the cation or the anion.

The toxic effects of ionic liquids are directly related to disruption of cell membrane. This is due to long alkyl chains, often presented in the cationic part of ionic liquids, which increase the lipophilic character of the ionic liquids molecule. It has been confirmed that the toxicity of ionic liquids is associated with their lipophilic character and membrane damage. However, ammonium tetrafluoroborate does not contain any lipophilic alkyl chains.

There are results obtained by electrospray ionization mass spectrometry, NMR spectroscopy, and pH measurements that clearly indicate that hydrolysis is a process restricted to ([PF6]- and) [BF4]-, while imidazolium cation remains unchanged. Hydrolysis of [BF4]- was observed under all of the experimental conditions used, even at room temperature.

Apart from ammonium ions, hydrogen fluoride is probably formed when ammonium tetrafluoroborate is being dissolved in aquatic environment. In aqueous form it is called hydrofluoric acid. Hydrogen fluoride is only a weak acid in dilute aqueous solution. This is in part a result of the strength of the hydrogen-fluorine bond, but also of other factors such as the tendency of HF, H2O, and F− anions to form clusters.
Hydrogen fluoride is not included in Reproductive and Developmental Toxicants, a 1991 report published by the U.S. General Accounting Office (GAO) that lists 30 chemicals of concern because of widely acknowledged reproductive and developmental consequences. Fluoride crosses the placenta, and at low doses is thought to be essential for normal fetal development in humans. It is rarely excreted in breast milk. There have been rare cases of mottling of deciduous teeth in infants born to mothers who had high daily intakes of fluoride during pregnancy; skeletal abnormalities are considered unlikely. No reproductive effects due to hydrogen fluoride are known.
It has also been concluded by Slooff (1998) that the limited data available indicate that accumulation through food chains (biomagnification) is of little significance in the aquatic environment.
In one study it was especially noted that in none of the animal carcinogenicity studies effects on morphology of any of the reproductive organs were found. Effects on on the reproduction are systemic and HF occurs in the systemic circulation only as a free ionic or as organically bound fluoride rather tan as HF or NaF. In several studies, the effect of fluoride on the testes of mice, rats and rabbits with respect to reproductive impairment was tested. In none of these studies the fluoride anion content of the control diet was stated. In natural water, fluoride ions form strong complexes with aluminium, and fluorine chemistry in water is largely regulated by aluminium concentration and pH. Below pH 5, fluorine is almost entirely complexed with aluminium and consequently, the concentration of free F- is low. As the pH increases, Al-OH complexes dominate over Al-F complexes and the free F level increases. The dominant Al-F complex at pH <5 is AlF2+) is of little significance in the aquatic environment.

Data source

Reference

Reference 1

Reference Type:

study report

Title:

Unnamed

Year:

2001

Reference 2

Reference Type:

publication

Title:

Toxicity mechanisms of ionic liquids.

Author:

Marina Cvjetko Bubalo, Kristina Radošević, Ivana Radojčić Redovniković, Igor Slivac, and
Višnja Gaurina Srček

Year:

2017

Bibliographic source:

Arh Hig Rada Toksikol, 2017;68:171-179

Reference 3

Reference Type:

publication

Title:

Hydrolysis of Tetrafluoroborate and Hexafluorophosphate Counter Ions in Imidazolium-Based Ionic Liquids.

Author:

Mara G. Freire, Catarina M. S. S. Neves, Isabel M. Marrucho, Joa˜o A. P. Coutinho, and Ana M. Fernandes.

Year:

2009

Bibliographic source:

J. Phys. Chem. A 2010, 114, 3744–374

Reference 4

Reference Type:

review article or handbook

Title:

Kirk-Othmer Encyclopedia of Chemical Technology. 4th ed. Volumes

Year:

1994

Bibliographic source:

Kirk-Othmer Encyclopedia of Chemical Technology. 4th ed. Volumes 1: New York, NY. John Wiley and Sons, 1991-Present., p. V11: 313 (1994)