Spiro[piperidine-1,1'-pyrrolidinium] bifluoride

Endpoint summary

Description of key information

5-Azoniaspiro[4.5]decane, hydrogene difluoride is considered to be corrosive to the skin

Key value for chemical safety assessment

Skin irritation / corrosion

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (corrosive)

Eye irritation

Endpoint conclusion

Endpoint conclusion:

no study available

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

5-Azoniaspiro[4.5]decane, hydrogene difluoride is a quaternary ammonium salt with the  anion hydrogene difluoride. The cationic 5-azoniaspiro[4.5]decane is moreover a spiro-compound, due to the two cycloalkyls (one clyclohexyl, one cyclopentyl) connected solely via the nitrogen atom.

The substance is a white crystalline solid in anhydrous surroundings. Due to a strongly hygroscopic character it will change its appearance to moist-sticky or even liquid under humid conditions, depending on the amount of water that is absorbed.

The substance was tested for its skin corrosive properties in vitro on reconstructed human epidermidis according to OECD TG 431. However, under the conditions of the assay the test item became electrostatically charged and an even distribution on the epidermal surface could not be achieved. Accordingly, the results obtained (cell viabilities of 99 % after 3 min exposure and 30 % after 60 min exposure, Wingenroth, 2017), not indicating corrosivity, might not reflect accurately the substance’s properties and might underestimate the irritant/corrosive potential. Therefore, the cell viabilities determined in this assay were considered as underestimated and not reliable.

As this technical difficulty is related to the physicochemical characteristics of the material it is expected to occur in any other in vitro skin/eye irritation assay and therefore no further testing was conducted with respect to skin or eye corrosion/irritation.

Consequently, an alternative approach for the assessment of irritation/corrosion was chosen. A QSAR toolbox analysis (QSAR OECD Toolbox, version: 3.4, 2016), in a first attempt, does not reveal a reliable result with respect to skin or eye corrosion/irritation.

As second approach the anion hydrogene diflouride was assessed. Hydrogene difluoride is in equilibrium with hydrogene fluoride (Hollemann Wiberg, Lehrbuch der Anorganischen Chemie, 91.-100. edition, Walter de Gruyter Verlag, Berlin, New York, 1985).

3 HF ↔ H2F+ + HF2-              [Ion product at 0 °C: ca. 10 - 10.7]

Thus, read across to hydrogene fluoride is plausible for the assessment of irritation/corrosion. The MAK Commission (German Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area) assessed hydrogene fluoride and its aqueous solutions as highly irritating or corrosive to the skin and mucous membranes.  “Clinical manifestations after dermal exposure, which often do not occur until hours later, are pronounced pain, swelling, persistent coagulation and blistering” (2015. Hydrogen fluoride [MAK Value Documentation, 2001]. The MAK Collection for Occupational Health and Safety. 1–24).

Based on a worst case assessment and taking into account the available data on hydrogene fluoride a corrosive potential is assumed for 5-Azoniaspiro[4.5]decane, hydrogene difluoride. The legal classification of hydrogene fluoride as Skin Corr. 1A is therefore also valid for 5-Azoniaspiro[4.5]decane, hydrogene difluoride.

Justification for classification or non-classification

In vitro testing for skin and eye irritation/corrosion of 5-Azoniaspiro[4.5]decane, hydrogene difluoride was technically not feasible. Based on a worst case assessment and taking into account the available data on hydrogene fluoride a corrosive potential is assumed for 5-Azoniaspiro[4.5]decane, hydrogene difluoride. The legal classification of hydrogene fluoride as Skin Corr. 1A is considered appropriate for 5-Azoniaspiro[4.5]decane, hydrogene difluoride.