Zinc sulphide

Skin irritation / corrosion

Administrative data

Endpoint:

skin irritation: in vivo

Type of information:

migrated information: read-across based on grouping of substances (category approach)

Adequacy of study:

key study

Study period:

Not reported

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study well documented, meets generally accepted scientific principles, acceptable for assessment

Justification for data waiving:

other:

Cross-reference

Cross-reference 1

Reason / purpose for cross-reference:

reference to same study

Cross-reference 2

Reason / purpose for cross-reference:

reference to other study

Data source

Reference

Reference Type:

publication

Title:

Unnamed

Year:

1991

Materials and methods

Test guideline

Qualifier:

no guideline followed

Deviations:

not applicable

Principles of method if other than guideline:

Macroscopic skin reactions, skin histological changes and epidermal keratin binding of test material were observed in New Zealand White rabbits after 5 d application of test material to skin using both open and occlusive patch methods.

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

Zinc oxide

EC Number:

215-222-5

EC Name:

Zinc oxide

Cas Number:

1314-13-2

Molecular formula:

OZn

IUPAC Name:

oxozinc

Details on test material:

- Name of test material (as cited in study report): Zinc oxide
- Analytical purity: 98 % (minimum)
- Storage condition of test material: Test suspension in 0.1 % Tween 80 was prepared 24 h before use and stored at 4 °C.

Test animals

Species:

rabbit

Strain:

New Zealand White

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Sex: Male
- Source: Charing Cross and Westminster Medical School, London, UK
- Weight at study initiation: 2.5-4.0 kg
- Housing: Housed singly
- Diet: R14 pellets (Biosure) (zinc content 74 mg/kg, w/w)
- Water: Tap water
- Acclimation: Acclimatized to conventional restraining boxes before open patch test


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 18±2
- Humidity (%): 45
- Photoperiod (h dark/h light): 12/12

Test system

Type of coverage:

other: Both open and occlusive in two different tests

Preparation of test site:

other: Clipped

Vehicle:

other: 0.1 % Tween 80

Controls:

yes, concurrent vehicle

Amount / concentration applied:

TEST SOLUTION
- Amount(s) applied (volume): 0.5 mL
- Concentration (if solution): 20 % (w/v) zinc oxide suspension in 0.1 % Tween 80
- pH: 7.4

Duration of treatment / exposure:

5 d

Observation period:

Open patch test: Observed during and after 5 d exposure period
Occlusive patch test: On Day 3 and Day 5

Number of animals:

Four animals each for control and test groups in both open and occlusive patch test

Details on study design:

Open patch test: Eight test sites (5 cm2) were designated, four on each side of the mid-dorsal line. Test suspension or vehicle was applied daily for 5 successive days. The animals were restrained for 30 min to allow test sites to dry. Skin sites were observed during and after 5 d exposure period. Rabbits were killed 24 h after the fifth daily treatment.

Occlusive patch test: Animals were prepared similar to open patch test. Test suspension or vehicle was applied to the skin on a sterile gauze pad that was secured by a hypoallergenic adhesive tape. The trunks of these animals were wrapped in rubberized fabric and impermeable dressing for 3 d. At this stage, dressings were removed and skin sites were evaluated for irritancy. Two rabbits were killed at this stage. The remaining animals were redressed with freshly impregnated gauze pads and then re-examined and killed after a further 2 d.

In both tests, representative samples of each test and control skin sites of killed animals were preserved in 10 % phosphate buffered formalin for histology. Thin sections cut along the anterior-posterior axis were stained with haematoxylin and eosin, or with morin dye, which fluoresces blue-green in the presence of zinc ions and ultraviolet light (to demonstrate zinc binding to epidermal keratin histologically).

SCORING SYSTEM: Not reported

Results and discussion

In vivo

Results

Irritation parameter:

other: Score not reported

Irritant / corrosive response data:

No obvious reactions were observed in both control and treatment groups in any of the performed tests after 5 d exposure.

Other effects:

Histological changes: No evidence of damage was observed.

Morin fluorescence for zinc on skin: No obvious reaction was observed.

Any other information on results incl. tables

None

Applicant's summary and conclusion

Interpretation of results:

not irritating

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

Based on these results, 20 % w/v zinc oxide was found to be non-irritating to rabbit skin.

Executive summary:

A study was conducted to evaluate the skin irritation potential of zinc oxide in New Zealand White rabbits by both open and occlusive patch methods.

In open patch test, 0.5 mL of 20 % w/v zinc oxide suspension in 0.1 % Tween 80 or vehicle was applied to clipped sites (5 cm²) of groups of four animals for 5 d. Skin sites were observed during and after 5 d exposure period. Animals were killed 24 h after the fifth daily treatment.

In occlusive patch test, groups of four animals were treated similarly to open patch test, but the test suspension or vehicle was applied to the skin using occlusive dressing for 3 d. After 3 d, dressings were removed and skin sites evaluated for irritancy. Two rabbits were killed at this stage. The remaining animals were redressed with freshly impregnated gauzes and then re-examined and killed after a further 2 d.

In both tests, representative samples of each test and control skin site of killed animals were analysed histologically and stained with morin dye to study epidermal keratin binding of zinc.

No obvious reactions were observed in both control and treatment groups in any of the performed tests after 5 d exposure. No evidence of damage was observed upon histological examination. No morin fluorescence was observed in skin sections.

Based on these results, 20 % w/v zinc oxide was found to be non-irritating to rabbit skin.