Sodium hydrogendifluoride

Endpoint summary

Description of key information

A proprietary skin irritation study on potassium hydrogen difluoride is available. The results of this study indicate that solid substance is not irritating or corrosive.  However, the study is not considered to be directly relevant to human exposure: the test animal (rabbit) does not sweat; humans sweat therefore if solid substance came into contact with damp skin, HF would be generated which is corrosive. The substance is therefore considered likely to be corrosive and should be classified as such, as a precautionary approach.

Key value for chemical safety assessment

Skin irritation / corrosion

Link to relevant study records

Reference

Endpoint:

skin irritation: in vivo

Type of information:

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

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: The test parameters evaluated in this study are well documented and scientifically acceptable. The study was conducted according to Good Laboratory Practice regulations.

Qualifier:

according to guideline

Guideline:

other: U.S. Federal Regulations, Title 49, Transportation Revised Oct. 1, 1979, Appendix A - Method of Testing Corrosion to Skin.

GLP compliance:

yes

Species:

rabbit

Strain:

New Zealand White

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Summit View Farm, Belvidere, NJ
- Age at study initiation: 10-12 weeks
- Housing: individually in suspended stainless steel wire mesh cages
- Diet (e.g. ad libitum): Purina Rabbit Chow 5321 from W.F. Fisher & Son; at libitum except while dosing and observing
- Water (e.g. ad libitum): tap water adlibitum except while dosing and observing
- Acclimation period: 14 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20 +/- 4
- Humidity (%): 50 +/- 5
- Photoperiod (hrs dark / hrs light): 12/12

Type of coverage:

occlusive

Preparation of test site:

other: shaved 1 day before dosing

Vehicle:

unchanged (no vehicle)

Controls:

other: Each test animal received a concurrent negative control patch

Amount / concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 0.5 g

Duration of treatment / exposure:

4 hours

Observation period:

At 4 hours, immediately after patch removal and again at 48 hours (44 hours after patch removal)

Number of animals:

six

Details on study design:

TEST SITE
- Area of exposure: 1 X 1 inch square area under a 1 X 1 inch square guaze patch
- Type of wrap if used: Gauze patches wese secured to the skin with Blenderm surgical tape on all 4 edges, then impervious material (Saran Wrap) was used to occlude the patch sites

REMOVAL OF TEST SUBSTANCE
- Washing (if done): Test sites were washed with water
- Time after start of exposure: 4 hours

SCORING SYSTEM: Draize technique for evaluation of skin reactions

Irritation parameter:

erythema score

Basis:

mean

Time point:

other: 4 and 48 hours

Score:

ca. 0

Max. score:

4

Irritation parameter:

edema score

Basis:

mean

Time point:

other: 4 and 48 hours

Score:

ca. 0

Max. score:

4

Irritant / corrosive response data:

At 4 and 48 hours after exposure to potassium bifluoride, Draize scores of 0 for erythema and 0 for edema were observed.

Interpretation of results:

not irritating

Remarks:

Migrated information No signs of corrosion or skin irritation (erythema and/or edema). Criteria used for interpretation of results: EU

Conclusions:

No signs of skin corrosion or skin irritation (erythema and/or edema) were observed after topical (occluded) exposure to potassium bifluoride for 4-hours.

Executive summary:

Potassium bifluoride – solid substance is not irritating or corrosive with solid. However, the study is not relevant to humans: the test animal (rabbit) does not sweat; humans sweat therefore if solid substance came into contact with damp skin, HF would be generated which is corrosive.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (corrosive)

Eye irritation

Link to relevant study records

Reference

Endpoint:

eye irritation

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Endpoint conclusion

Endpoint conclusion:

no study available

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Skin irritation

A proprietary skin irritation study on sodium hydrogen difluoride is available. The results of the study indicate that the solid substance is not irritating or corrosive. However, the study is considered to be of limited relevance to human exposure: the test animal (rabbit) does not sweat; humans sweat therefore if solid substance came into contact with damp skin, corrosive HF would be generated. The EU RAR for HF notes that, in humans, dermal contact with HF can cause second and third degree burns which are associated with severe pain and which heal very slowly. The substance is therefore considered likely to be corrosive and should be classified as such, as a precautionary approach.

Eye irritation

No study has been performed, given the likely generation of the corrosive substance HF under the study conditions. It is considered likely that the substance is corrosive and a severe eye irritant and should be classified as such.

Justification for selection of skin irritation / corrosion endpoint:
A proprietary skin irritation study on potassium hydrogen difluoride is available. The results of this study indicate that solid substance is not irritating or corrosive. However, the study is not considered to be directly relevant to human exposure: the test animal (rabbit) does not sweat; humans sweat therefore if solid substance came into contact with damp skin, HF would be generated which is corrosive. The substance is therefore considered likely to be corrosive and should be classified as such, as a precautionary approach.

Justification for selection of eye irritation endpoint:
In accordance with Column 2 of the Annex VIII REACH data requirements (specific rules for adaptation from Column 1), a study does not need to be conducted because the substance is classified as corrosive.

Effects on skin irritation/corrosion: corrosive

Effects on eye irritation: corrosive

Justification for classification or non-classification

Sodium hydrogen difluoride is classified according to the CLP Regulation (EC) 1272/2008 in Skin Corrosion Class 1B. This classification is consistent with the data reviewed and no change is proposed.