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Description of key information

Skin sensitization (equivalent to 406), GPMT and Buehler: sensitizing

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records

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Endpoint:
skin sensitisation: in vivo (non-LLNA)
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
comparable to guideline study
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 406 (Skin Sensitisation)
GLP compliance:
yes
Type of study:
guinea pig maximisation test
Justification for non-LLNA method:
The study was performed prior to the implementation of the LLNA method.
Species:
guinea pig
Strain:
Hartley
Sex:
female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Breeding Laboratories, Inc., Wilmington, MA
- Age at study initiation: 5-6 weeks of age
- Weight at study initiation: 204 - 315 g
- Housing: individually housed in wiremesh cages
- Diet (e.g. ad libitum): NIH Amimal Feed A, certified feed, Zeigler Brothers, Gardners, PA - ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: 14 days

ENVIRONMENTAL CONDITIONS
- Housed in an environmentally controlled room
- Photoperiod (hrs dark / hrs light): 12/12


Route:
intradermal and epicutaneous
Vehicle:
propylene glycol
Concentration / amount:
Day 0 Induction: Intradermal injection of 3% MEKO in propylene glycol and intradermal injection of 1% MEKO in Freunds Complete Adjuvent.
Day 7 Induction: Topical occluded patch with 0.3 mL of undiluted MEKO
Route:
epicutaneous, occlusive
Vehicle:
propylene glycol
Concentration / amount:
Day 21 Challenge: Topical occluded patch with 0.2 mL of 50% MEKO in propylene glycol to left side and topical occluded patch with 0.2 mL of undiluted MEKO on the right side.
No. of animals per dose:
10
Details on study design:
RANGE FINDING TESTS:
For topical applications under occlusion, concentrations of 25, 50, 75 MEKO in propylene glycol and 100% MEKO were applied for 24 hours and the skin evaluated for irritation potential.
For intradermal injections, concentrations of 0.1, 1, 3, and 5% MEKO in propylene glycol and in Freunds Complete Adjuvent (FCA) were evaluated for irritation potential. 3% MEKO in propylene glycol and 1% MEKO in FCA was chosen for induction on day 0.

Challenge controls:
Vehicle control group
Positive control substance(s):
yes
Remarks:
1-chloro-2, 4-dinitrobenzend (DNCB)
Positive control results:
The positive control showed the expected effects.
Reading:
1st reading
Hours after challenge:
24
Group:
test chemical
Dose level:
50% MEKO
No. with + reactions:
9
Total no. in group:
10
Remarks on result:
positive indication of skin sensitisation
Reading:
2nd reading
Hours after challenge:
48
Group:
test chemical
Dose level:
50% MEKO
No. with + reactions:
8
Total no. in group:
10
Remarks on result:
positive indication of skin sensitisation
Reading:
1st reading
Hours after challenge:
24
Group:
negative control
Dose level:
50% MEKO
No. with + reactions:
0
Total no. in group:
10
Remarks on result:
no indication of skin sensitisation
Reading:
2nd reading
Hours after challenge:
48
Group:
negative control
Dose level:
50% MEKO
No. with + reactions:
0
Total no. in group:
10
Remarks on result:
no indication of skin sensitisation
Reading:
1st reading
Hours after challenge:
24
Group:
positive control
Dose level:
0.1% DNCB
No. with + reactions:
10
Total no. in group:
10
Remarks on result:
positive indication of skin sensitisation
Reading:
2nd reading
Hours after challenge:
48
Group:
positive control
Dose level:
0.1% DNCB
No. with + reactions:
10
Total no. in group:
10
Remarks on result:
positive indication of skin sensitisation
Interpretation of results:
Category 1 (skin sensitising) based on GHS criteria
Conclusions:
Methyl ethyl ketoxime is a strong skin sensitizer in guinea pigs.
Endpoint:
skin sensitisation: in vivo (non-LLNA)
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
comparable to guideline study
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 406 (Skin Sensitisation)
GLP compliance:
yes
Type of study:
Buehler test
Justification for non-LLNA method:
The study was performed prior to the implementation of the LLNA method.
Species:
guinea pig
Strain:
Hartley
Sex:
female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Harlan Sprague Dawley, Inc., Indianapolis, IN
- Weight at study initiation: 300-400 g
- Housing: One per cage in suspended wire mesh bottom cage.
- Diet (e.g. ad libitum): Agway Prolab Guinea Pig Chow, ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: at least 7 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 64-79
- Humidity (%): 40-70
- Photoperiod (hrs dark / hrs light): 12/12


Route:
epicutaneous, occlusive
Vehicle:
propylene glycol
Concentration / amount:
25%
Route:
epicutaneous, occlusive
Vehicle:
propylene glycol
Concentration / amount:
5%
No. of animals per dose:
10
Details on study design:
RANGE FINDING TESTS:
A volume of 0.3 mL of concentrations of 100% (neat), 50, 25 and 10% MEKO in propylene glycol were evaluated for irritation potential.
A volume of 0.3 mL of concentrations of 1 and 5% MEKO in propylene glycol were evaluated for irritation potential.

MAIN STUDY
A. INDUCTION EXPOSURE
- No. of exposures: 9
- Exposure period: 24 hours for each of 9 induction applications
- Test groups: 10
- Control group: 5
- Site: one flank used for all 9 induction applications
- Frequency of applications: every other day
- Duration: 24 hours/application
- Concentrations: 25% MEKO w/v in propylene glycol; a volume of 0.3 mL was applied


B. CHALLENGE EXPOSURE
- No. of exposures: 1
- Day(s) of challenge: 2 weeks after last induction application
- Exposure period: 24 hours
- Test groups: 10
- Control group: 5
- Site: flank not exposed to induction applications
- Concentrations: 5% MEKO w/v in propylene glycol: a volume of 0.3 mL was applied
- Evaluation (hr after challenge): 24 and 48 hours


OTHER: A second challenge was performed 1 week after the first challenge at 5% MEKO w/v in propylene glycol
Challenge controls:
Five guinea pigs were dosed with 0.3 mL of propylene glycol 9 times for induction. The same 5 guinea pigs were dosed at challenge with 0.3 mL of 5% MEKO in propylene glycol.
Positive control substance(s):
yes
Remarks:
dinitrochlorobenzene
Positive control results:
Positive allergic contact sensitization occurred in 10 of 10 positive control guinea pigs, thus validating the test procedure.
Reading:
1st reading
Hours after challenge:
24
Group:
test chemical
Dose level:
25% induction, 5% challenge
No. with + reactions:
6
Total no. in group:
10
Clinical observations:
erythema
Reading:
2nd reading
Hours after challenge:
48
Group:
test chemical
Dose level:
25% induction, 5% challenge
No. with + reactions:
5
Total no. in group:
10
Clinical observations:
erythema
Reading:
1st reading
Hours after challenge:
24
Group:
negative control
Dose level:
0% induction, 5% challenge
No. with + reactions:
0
Total no. in group:
10
Clinical observations:
none
Reading:
2nd reading
Hours after challenge:
48
Group:
negative control
Dose level:
0% induction, 5% challenge
No. with + reactions:
0
Total no. in group:
10
Clinical observations:
none
Reading:
1st reading
Hours after challenge:
24
Group:
positive control
Dose level:
0.1% dintrochlorobenzene
No. with + reactions:
10
Total no. in group:
10
Clinical observations:
erythema, eschar, edema
Reading:
2nd reading
Hours after challenge:
48
Group:
positive control
Dose level:
0.1% dinitrochlorobenzene
No. with + reactions:
10
Total no. in group:
10
Clinical observations:
erythema, eschar, edema
Reading:
rechallenge
Hours after challenge:
24
Group:
test chemical
Dose level:
25% induction, 5% challenge
No. with + reactions:
9
Total no. in group:
10
Clinical observations:
erythema
Reading:
rechallenge
Hours after challenge:
48
Group:
test chemical
Dose level:
25% induction, 5% challenge
No. with + reactions:
8
Total no. in group:
10
Clinical observations:
erythema
Interpretation of results:
other: Category 1B based on CLP criteria (EU criteria according to Regulation (EC) No. 1272/2008)
Conclusions:
Methyl ethyl ketoxime induced allergic contact dermatitis in guinea pigs in this modified Buehler closed-patch skin sensitisation study.
Endpoint conclusion
Endpoint conclusion:
adverse effect observed (sensitising)
Additional information:

The test substance was a skin sensitiser when evaluated in guinea pigs. In the guinea pig maximisation test, conducted by Food & Drug Research Laboratories, Inc. (1983), animals were induced intradermally with 3% the test substance in propylene glycol, followed by epidermal induction on day 7 with 0.3 mL of undiluted the test substance under occlusion. On day 21, animals were challenged epidermally with 0.2 mL of 50% the test substance in propylene glycol on the left side and 0.2 mL of undiluted the test substance on the right side under occlusion. At least 80% of animals exhibited a positive response. Positive and negative controls were valid, confirming the reliability of the used test method.

 

A test using a similar protocol (4% intracutaneous induction, 100% occlusive epicutaneous induction, and a 50% occlusive epicutaneous challenge) resulted in a 70 percent sensitisation rate (RCC NOTOX, 1989).

 

When evaluated by the Buehler method (Springborn Life Sciences, Inc., 1989) guinea pigs were induced epidermally with 25% the test substance in propylene glycol, using 9 occluded 24-hour exposures every other day. This was followed by epicutaneous challenge with 5% the test substance in propylene glycol under occlusion. Results were scored 24 and 48 hours after the test patch removal. Positive reactions were observed in 6 of 10 animals. Upon rechallenge with 5% the test substance, positive responses were observed in 9 of 10 animals. Based on these results, the test substance is concluded to be sensitising in guinea pigs.

 

Also a local lymph node assay (LLNA) in mice, performed under GLP and according to OECD Guideline 429 (2009) is available. The stimulation indices were 1.3 and 1.0 for 50% (acetone : olive oil in 4:1 (v/v) ratio was used as a vehicle) and 100% the test substance, respectively. The study gave thus a negative result. The positive control behaved accordingly. According to CLP, a significant sensitising effect is defined by a stimulation index of >=3. Therefore, under the conditions of this study, butanone oxime is not sensitising.

The results of two GPMTs and one Buehler test all give solid support for the classification of butanone oxime as a skin sensitiser. The results of a recently and well-performed LLNA with butanone oxime did not show any evidence of skin sensitisation. Despite the negative result from the LLNA, the weight of evidence provided indicates that butanone oxime should be classified as a skin sensitiser. All three tests providing a positive result indicate classification in sub-category 1B.

 

Respiratory sensitisation

Endpoint conclusion
Endpoint conclusion:
no study available

Justification for classification or non-classification

Based on the available data the test substance is classified for skin sensitization category 1B (H317) according to Annex VI of Regulation (EC) 1272/2008.