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Toxicological information

Skin sensitisation

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Administrative data

Endpoint:
skin sensitisation: in vivo (non-LLNA)
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: guidline compliant study, used in EU risk assessment for zinc oxide

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1999

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 406 (Skin Sensitisation)
Qualifier:
according to
Guideline:
EU Method B.6 (Skin Sensitisation)
GLP compliance:
yes
Type of study:
guinea pig maximisation test
Justification for non-LLNA method:
The metals industry has historical data to indicate that metals can induce false positives/negatives in LLNA studies; this is confirmed from experiences in test labs.

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): zinc oxide
- Analytical purity: 99.69%

In vivo test system

Test animals

Species:
guinea pig
Strain:
Dunkin-Hartley
Sex:
female
Details on test animals and environmental conditions:
see reference

Study design: in vivo (non-LLNA)

Inductionopen allclose all
Route:
intradermal
Vehicle:
water
Concentration / amount:
see details on study design
Challengeopen allclose all
Route:
other: epidermal
Vehicle:
water
Concentration / amount:
see details on study design
No. of animals per dose:
10 in each test in main study
5 controls in each test
Details on study design:
Based on the results of a preliminary study, in the main studies experimental animals (10 in each test) were intradermally injected with a 20% concentration and epidermally exposed to a 50% concentration (i.e. the highest practically feasible concentration). Control animals (5 in each test) were similarly treated, but with vehicle (water) alone. Approximately 24 hours before the epidermal induction exposure all animals were treated with 10% SDS. Two weeks after the epidermal application all animals were challenged with a 50% test substance concentration and the vehicle.
Challenge controls:
see details on study designs
Positive control substance(s):
yes

Results and discussion

In vivo (non-LLNA)

Resultsopen allclose all
Reading:
1st reading
Hours after challenge:
24
Group:
test group
Dose level:
50 %
No. with + reactions:
4
Total no. in group:
10
Clinical observations:
Study 1
Remarks on result:
other: Reading: 1st reading. . Hours after challenge: 24.0. Group: test group. Dose level: 50 %. No with. + reactions: 4.0. Total no. in groups: 10.0. Clinical observations: Study 1.
Reading:
1st reading
Hours after challenge:
24
Group:
negative control
Dose level:
50 %
No. with + reactions:
0
Total no. in group:
5
Clinical observations:
Study 1
Remarks on result:
other: Reading: 1st reading. . Hours after challenge: 24.0. Group: negative control. Dose level: 50 %. No with. + reactions: 0.0. Total no. in groups: 5.0. Clinical observations: Study 1.
Reading:
1st reading
Group:
test group
Dose level:
50 %
No. with + reactions:
0
Total no. in group:
10
Clinical observations:
Study 2
Remarks on result:
other: Reading: 1st reading. Group: test group. Dose level: 50 %. No with. + reactions: 0.0. Total no. in groups: 10.0. Clinical observations: Study 2.
Reading:
1st reading
Group:
negative control
Dose level:
50 %
No. with + reactions:
1
Total no. in group:
5
Clinical observations:
Study 2
Remarks on result:
other: Reading: 1st reading. Group: negative control. Dose level: 50 %. No with. + reactions: 1.0. Total no. in groups: 5.0. Clinical observations: Study 2.

Applicant's summary and conclusion

Interpretation of results:
ambiguous
Remarks:
Migrated information
Conclusions:
conflicting results
Executive summary:

The skin sensitising potential of zinc oxide (purity 99.69%) was investigated in female Dunkin Hartley guinea pigs in two well-performed maximisation tests, conducted according to Directive 96/54/EC B.6 and OECD guideline 406. Based on the results of a preliminary study, in the main studies experimental animals (10 in each test) were intradermally injected with a 20% concentration and epidermally exposed to a 50% concentration (i.e. the highest practically feasible concentration). Control animals (5 in each test) were similarly treated, but with vehicle (water) alone. Approximately 24 hours before the epidermal induction exposure all animals were treated with 10% SDS. Two weeks after the epidermal application all animals were challenged with a 50% test substance concentration and the vehicle.In the first study, in response to the 50% test substance concentration skin reactions of grade 1 were observed in 4/10 experimental animals 24 hours after the challenge (40% sensitisation rate), while no skin reactions were evident in the controls. In contrast, in the second study no skin reactions were evident in the experimental animals (0% sensitisation rate), while a skin reaction grade 1 was seen in one control animal. The skin reaction observed in one control animal is most likely sign of non-specific irritation.