Niobium pentachloride

Endpoint summary

Description of key information

In an acute skin irritation/corrosion study in rabbits according to the method of Draize et al., niobium pentachloride was tested corrosive to the rabbit skin. In the same publication by Haley et al. (1962), the test substance was not eye irritating after conducting a study in rabbits according to Draize et al. However, in this study only 1 mg of the test item was applied to the rabbit eye, instead of the 100 mg as recommended in the current OECD guideline 405. Thus, the negative result of the study was disregarded, especially on the background that niobium pentachloride is readily dissolved forming hydrochloric acid when in contact with water.

Key value for chemical safety assessment

Skin irritation / corrosion

Link to relevant study records

Reference

Endpoint:

skin irritation: in vivo

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Publication, meets generally accepted scientific standards, well documented and acceptable for assessment

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 404 (Acute Dermal Irritation / Corrosion)

GLP compliance:

not specified

Species:

rabbit

Strain:

not specified

Type of coverage:

not specified

Preparation of test site:

other: abraded and unabraded

Vehicle:

not specified

Controls:

no

Observation period:

24 and 72 hours, 7 and 14 days

Number of animals:

6

Details on study design:

The author mentioned in the publication, that the method of Draize et al. (1944) was used to study skin irritation in rabbits. Niobium pentachloride was directly applied to unabraded and abraded rabbit skin.

Irritation parameter:

erythema score

Remarks:

unabraded skin

Basis:

mean

Time point:

other: 24 h, 72 h

Score:

4

Reversibility:

not reversible

Irritation parameter:

edema score

Remarks:

unabraded skin

Basis:

mean

Time point:

other: 24 h, 72 h

Score:

4

Reversibility:

not reversible

Irritation parameter:

other: eschar 25-30 mm in diameter

Basis:

mean

Time point:

other: within 7 days

Reversibility:

not reversible

Remarks on result:

other: No healing occurred and animals were sacrificed at 14 days

Irritation parameter:

overall irritation score

Remarks:

on abraded skin

Basis:

mean

Time point:

other: 24 h, 72 h

Score:

8

Max. score:

8

Reversibility:

not reversible

Remarks on result:

other: within 7 days perforating ulcers 25-30 mm in diameter with penetration through the skin.

Irritant / corrosive response data:

Direct application of niobium pentachloride to unabraded rabbit skin produced an irritation index of 4 within 24 hours for both edema and erythema. These reactions were still present at 72 hours. An eschar 25-30 mm in diameter formed within 7 days with the loss of the skin in the area. Healing did not occur and the animals were sacrificed at 14 days. A severe reaction occurred on abraded skin and resulted in the maximum irritation index of 8 within 24 hours. No change was observed at 72 hours, and within 7 days perforating ulcers 25-30 mm in diameter developed with penetration through the skin to the underlying muscle layers. When healing did not occur at 14 days, the animals were sacrificed.

Interpretation of results:

corrosive

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

In an acute dermal irritation/corrosion study according to the method of Draize et al. (1944), the test item is considered to be corrosive to the skin.

Executive summary:

In a primary dermal irritation study according to the method of Draize et al., six rabbits were dermally exposed to niobium pentachloride. Animals were observed for 1, 3, 7 and 14 days. On unabraded skin severe erythema and edema were formed within 24 hours continuing to eschars with 24-30 mm in diameter within 7 days that did not heal until day 14. On abraded skin, a maximum irritation index (8/8) was formed within 24 hours. No change was observed at 72 hours and perforating ulcers of 25-30 mm diameter size developed with penetration through the skin to the underlying muscle layers within 7 days. Healing did not occur during the 14 days observation period. Based on these findings, the test item is considered to be corrosive to the skin.

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

The potential of niobium pentachloride to cause irritating or corrosive effects to the abraded and unabraded skin was assessed by an in vivo study in rabbits. The test was performed according to the method of Draize et al. The target substance niobium pentachloride caused within 24 hours severe edema and erythrema that persists until 72 hours on the unabraded skin. An eschar 25-30 mm in diameter formed within 7 days with the loss of the skin in the area. Healing did not occur and the animals were sacrificed at 14 days. The observed enhanced severity of skin damage in abraded skin, in comparison to unabraded skin, was discussed to depend on the liberation of nascent hydrochloric acid by the tissue fluid. The published study fail to provide information on the duration of application as well as area of exposure and quantity applied. Yet, the performance of the study according to the method of Draize using the accepted rabbit model together with the study finding and details on the scoring system render the study sufficiently reliable. Thus, niobium pentachloride is classified as corrosive to the skin.

Due to the fact that the test item is corrosive to the skin, also severe eye damage can be expected, especially on the background that the target substance decomposes in water to hydrochloric acid.

Justification for selection of skin irritation / corrosion endpoint:
In vivo study following the method of Draize

Justification for selection of eye irritation endpoint:
An in vivo study was conducted following the method of Draize. But the study has one major methodological deficiency. Instead of applying 100 mg to the eye, as recommended by the OECD 405 guideline, only 1 mg of the test item was applied. Thus, the observed non-irritating effect of the test item in this study is due to the reduced dose which was applied and thus the natural buffering capacity of the lachrymal fluid was sufficient to counteract the nascent hydrochloric acid releases when the test item dissolved in the lachrymal fluid. Based on this background, the study was disregarded for the toxicological evaluation.

Effects on skin irritation/corrosion: corrosive

Justification for classification or non-classification

The test item caused severe and irreversible effects within 24 hours after application. The available data do not indicate a severe effects within <= 3 min. Therefore, classification as corrosive to the skin (H314) Category 1B is warranted. Due to rapid hydrolysis and subsequent generation of HCl, classification for H335 is warranted, which is in line with the harmonised classification of hydrochloric acid.