Tin bis(tetrafluoroborate)

Endpoint summary

Description of key information

Skin irritation: One reliable study for tin bis(tetrafluoroborate) is available (Chibanguza, 1986, OECD 404, non-GLP) which states that the test item (a 50% solution of tin bis(tetrafluoroborate)) has no skin irritating properties. Another study was initiated with tin bis(tetrafluoroborate) which shows severe irritation to skin. However, this study was disregarded (see discussion). In a weight of evidence approach, summarising two skin irritation studies conducted with tin bis(tetrafluoroborate) and one study performed with the structural analogue potassium tetrafluoroborate, tin bis(tetrafluoroborate) is considered to be non-irritating to skin.
Eye irritation: The structural analogue potassium tetrafluoroborate showed no irritation to eyes (OECD 405, GLP complaint). Nevertheless, due to possible mild pH effects upon dissolution of tin (bis)tetrafluoroborate in solution as well as the intrinsic redox potential it is discussed to classify tin bis(tetrafluoroborate) as irritant to eyes.

Key value for chemical safety assessment

Skin irritation / corrosion

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Eye irritation

Link to relevant study records

Reference

Endpoint:

eye irritation: in vivo

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP-compliant guideline study, available as unpublished report, no restrictions, fully adequate for assessment.

Qualifier:

according to guideline

Guideline:

OECD Guideline 405 (Acute Eye Irritation / Corrosion)

GLP compliance:

yes (incl. QA statement)

Species:

rabbit

Strain:

New Zealand White

Details on test animals or tissues and environmental conditions:

TEST ANIMALS
- Source: David Percival Ltd., Moston, Sandbach, Cheshire, U.K.
- Age at study initiation: ca. 12-16 weeks
- Weight at study initiation: 2.69-2.89 kg
- Housing: individually in suspended metal cages
- Diet: Spillers Rabbit Diet, Dalgety Agriculture Ltd., Almondsbury, Bristol, U.K., ad libitum
- Water: mains drinking water, ad libitum
- Acclimation period: at least 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 16-19
- Humidity (%): 49-65
- Air changes (per hr): ca. 15
- Photoperiod (hrs dark / hrs light): 12 / 12

Vehicle:

unchanged (no vehicle)

Controls:

other: untreated eye served as a negative control

Amount / concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 0.1 mL (ca. 99 mg)

Duration of treatment / exposure:

Single instillation

Observation period (in vivo):

72 hours

Number of animals or in vitro replicates:

3

Details on study design:

REMOVAL OF TEST SUBSTANCE
- Washing (if done): no

SCORING SYSTEM: Draize

TOOL USED TO ASSESS SCORE: ophthalmoscope

Irritation parameter:

cornea opacity score

Basis:

mean

Time point:

other: 24 + 48 + 72 hours

Score:

0

Max. score:

4

Irritation parameter:

iris score

Basis:

mean

Time point:

other: 24 + 48 + 72 hours

Score:

0

Max. score:

2

Irritation parameter:

conjunctivae score

Basis:

mean

Time point:

other: 24 + 48 + 72 hours

Score:

0.11

Max. score:

3

Reversibility:

fully reversible within: 48 hours

Irritation parameter:

chemosis score

Basis:

mean

Time point:

other: 24 + 48 + 72 hours

Score:

0

Max. score:

4

Irritant / corrosive response data:

Residual test material was noted around the treated eye of two animals one hour after treatment. No corneal or iridial effects were noted during the study. Chemosis was noted in all treated eyes one hour after treatment (score 1). Minimal conjunctival redness (score 1) persisted in one treated eye at the 24-hour observation. Treated eyes appeared normal 24-48 hours after treatment.

Interpretation of results:

not irritating

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

The test substance is not irritating to the eye.

Executive summary:

In a GLP-compliant OECD Guideline 405 study, rabbits were exposed to potassium tetrafluoroborate to test the eye irritation properties. 0.1 mL of the test material (ca. 99 mg) was instilled in one eye of three rabbits and the eyes were observed after 1, 24, 48 and 72 hours. Untreated eyes served as negative control. Residual test material was noted around the treated eye of two animals one hour after treatment. No corneal or iridial effects were noted during the study. Chemosis was noted in all treated eyes one hour after treatment (score 1). Minimal conjunctival redness persisted in one treated eye at the 24-hour observation (score 1; mean score at 24 + 48 + 72 hours for three animals 0.11). Treated eyes appeared normal 24-48 hours after treatment. Based on the results of the study, potassium tetrafluoroborate was concluded to be not irritating to eyes.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (irritating)

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Additional information

Read-across concept (human health) for tin bis(tetrafluoroborate):

Substance-specific toxicity data for the substance tin bis(tetrafluoroborate) (water solubility >50 % w/w) are not available. However, since upon dissolution in water, full dissociation of the highly water-soluble tin bis(tetrafluoroborate) to (i) Sn²⁺cations and (ii) tetrafluoroborate anions occurs, read-across to (i) inorganic tin(II) substances and (ii) inorganic salts of tetrafluoroboric acid is made, respectively.

This read-across is considered fully justified in view of the comparable water solubilities of the similarly soluble read-across substances, such as (i) tin(II)chloride, water solubility 178 g/L at 20°C, and (ii) potassium tetrafluoroborate, water solubility 5.4 g/L at 22°C.

Whereas it is noted that upon dilution of aqueous solutions, “clouding” and precipitation of basic tin salts occurs , which can be described by the following equation:

SnX₂+ H₂O <--> "SnXOH"(s) + HX

this Sn²⁺-specific behaviour is not considered to restrict the read-cross since oral bioavailability of inorganic tin(II) substances is generally very low.

Potassium tetrafluoroborate is currently not classified according to the criteria specified by Directive 67/548/EEC and subsequent regulations, and is correspondingly considered not to require classification according to the criteria set forth by EC Regulation No. 1272/2008 and subsequent regulations, neither for human health or environmental hazards.

Any toxicological or ecotoxicological hazards (if any) are therefore assumed to be related to Sn²⁺only.

Skin irritation

One reliable study for tin bis(tetrafluoroborate) is available (Chibanguza, 1986, OECD 404, non-GLP) which states that the test item (a 50% solution of tin bis(tetrafluoroborate)) has no skin irritating properties. Another study was initiated with tin bis(tetrafluoroborate) (stannous fluoroborate solution as stated in the test report) which shows severe irritation to skin. However, this study was disregarded due to lack of reliable substance-specific data. Based on the outcome of the test, showing corrosive effects to rabbit skin, it can strongly be assumed that tin bis(tetrafluoroborate) used for testing contains a significant content of free acid, which mainly causes the skin corrosion in rabbits. This theory is proved by one further study performed with the structural analogue potassium tetrafluoroborate. The reliable study (Anonymous, 1992, OECD 404, GLP) stated that potassium tetrafluoroborate is non-irritating to rabbit skin.

In a weight of evidence approach, summarising two skin irritation studies conducted with tin bis(tetrafluoroborate) and one performed with the structural analogue potassium tetrafluoroborate, tin bis(tetrafluoroborate) is considered to be non-irritating to skin.

Eye irritation

One reliable study was conducted with the structural analogue potassium tetrafluoroborate (GLP-compliant OECD guideline 405). No corneal or iridial effects were noted during the study. Chemosis was noted in all treated eyes one hour after treatment (score 1). Minimal conjunctival redness persisted in one treated eye at the 24-hour observation (score 1; mean score at 24 + 48 + 72 hours for three animals 0.11). All treated eyes appeared normal 24-48 hours after treatment. Based on results of the study, potassium tetrafluoroborate is not irritating to eyes.

 

Results of the study performed with potassium tetrafluoroborate were considered for classification and labelling of tin (bis)tetrafluoroborate. Nevertheless, possible mild pH effects upon dissolution of tin (bis)tetrafluoroborate in solution as well as the intrinsic redox potential (released Sn²⁺ions may oxidise rapidly), may contribute to a certain irritation potential. Given these substance-specific properties and the lack of substance-specific eye irritation data, in a conservative approach it is safely assumed that tin bis(tetrafluoroborate) is irritant to the eyes.

Justification for selection of skin irritation / corrosion endpoint:
There are two reliable studies available, covering the skin irritation endpoint for tin bis(tetrafluoroborate). One study was conducted with tin bis(tetrafluoroborate) - 50% solution, the other study were performed with the structural analogue potassium tetrafluoroborate. In a weight of evidence approach it was discussed that tin bis(tetrafluoroborate) is not irritating to skin.

Justification for selection of eye irritation endpoint:
There are one reliable study available, covering the eye irritation endpoint for tin bis(tetrafluoroborate).The study was performed with the structural analogue potassium tetrafluoroborate. No effects in eye observed. However, based on mild pH effects upon dissolution of tin (bis)tetrafluoroborate in solution as well as the intrinsic redox potential it is safely assumed that tin bis(tetrafluoroborate) is irritant to eyes (see justification for classification or non-classification.

Effects on eye irritation: irritating

Justification for classification or non-classification

Skin irritation:

Based on a weight of evidence approach discussed above tin bis(tetrafluoroborate) should not be labelled as skin irritant in accordance with Directive 67/548/EEC and according to the EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation (EC) No. 1272/2008.

Eye irritation:

No substance specific information for tin bis(tetrafluoroborate) are available. Nevertheless, one study was performed with the structural analogue potassium tetrafluoroborate, that does not show any hints on eye irritating properties and is thus not to be classified according to Directive 67/548/EEC and according to the EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation (EC) No. 1272/2008.

However, based on the assumption that local effects occurring from tin bis(tetrafluoroborate) are related to the cation only (see read-across concept) and taking into account the possible mild pH effects upondissolution of tin (bis)tetrafluoroborate in solution as well as the intrinsic redox potential, in a conservative approach it is safely be assumed that tin bis(tetrafluoroborate) is irritant to the eyes. Hence,tin bis(tetrafluoroborate) should be classified according to the EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation (EC) No. 1272/2008 safely as irritating to the eye (Eye Irrit. Cat. 2) and according to Directive 67/548 EC with R36.

Respiratory irritation:

The classification as respiratory irritant is covered under the endpoint specific target organ toxicity- single exposure and repeated exposure. Please refer to the endpoint summaries on acute toxicity (endpoint 7.2) and repeated dose toxicity (endpoint 7.5) for further information.