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Toxicological information

Skin irritation / corrosion

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Administrative data

Endpoint:
skin irritation: in vivo
Type of 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:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Justification for type of information:
See appendix on read across in iuclid section 13

Data source

Reference
Reference Type:
publication
Title:
Unnamed
Year:
1991

Materials and methods

Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
Macroscopic skin reactions, skin histological changes and epidermal keratin binding of the test material were observed in TO mice after 5 d application of test material to skin using open patch test.
GLP compliance:
not specified

Test material

Reference
Name:
Unnamed
Type:
Constituent
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:
mouse
Strain:
other: TO (outbred) strain
Details on test animals and environmental conditions:
TEST ANIMALS
- Sex: Male
- Source: Charing Cross and Westminster Medical School, London, UK
- Age at study initiation: 8-10 wk
- Diet: Complete rodent diet (CRM, Biosure, Cambridge, UK) (zinc content 65 mg/kg, w/w), ad libitum
- Water: Deionized water, ad libitum

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22±2
- Humidity (%): 55
- Photoperiod (h dark/h light): 12/12


Test system

Type of coverage:
open
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:
Observed during and after 5 d exposure period
Number of animals:
Six animals both in test and control group
Details on study design:
Sites of 5 cm2 were treated with the test suspension or vehicle for 5 consecutive days. Animals were gently anaesthetized with ether until the test sites had dried. Skin sites were observed during and after 5 d exposure period.

24 h after the fifth daily treatment, animals were killed and representative samples of each test and control skin sites 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

Resultsopen allclose all
Irritation parameter:
erythema score
Basis:
mean
Time point:
72 h
Score:
0
Max. score:
8
Reversibility:
not specified
Remarks on result:
no indication of irritation
Irritation parameter:
erythema score
Time point:
24 h
Remarks on result:
not measured/tested
Irritation parameter:
erythema score
Time point:
48 h
Remarks on result:
not measured/tested
Irritation parameter:
edema score
Time point:
24/48/72 h
Remarks on result:
not measured/tested
Irritant / corrosive response data:
No obvious reactions were observed in both control and test groups 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 mouse skin.
Executive summary:

A study was conducted to evaluate the skin irritation potential of zinc oxide in TO (outbred) strain mice.

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 six animals for 5 consecutive days. Skin sites were observed during and after 5 d exposure period. 24 h after the fifth daily treatment, animals were killed and representative samples of each test and control skin sites 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 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 mouse skin.