Mecoprop

Skin sensitisation

Administrative data

Endpoint:

skin sensitisation: in vivo (non-LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

17 August 1983 to 15 September 1983

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1984

Report date:

1984

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 406 (Skin Sensitisation)

GLP compliance:

yes (incl. QA statement)

Type of study:

guinea pig maximisation test

Justification for non-LLNA method:

The study pre-dates the introduction of the LLNA method.

Test material

Test material information

Constituent 1

Reference substance name:

Mecoprop

EC Number:

230-386-8

EC Name:

Mecoprop

Cas Number:

7085-19-0

Molecular formula:

C10H11ClO3

IUPAC Name:

2-(4-chloro-2-methylphenoxy)propanoic acid

Test material form:

solid

Details on test material:

- Physical appearance: Yellowish-brown

Specific details on test material used for the study:

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- Preparation of the test material formulations: Immediately before test material application with Ultraturrax or with a magnetic stirrer. Formulations of the test material were prepared gravimetrically. The test material was prepared in at appropriate concentrations in distilled water (aqua dest.), distilled water and paraffin oil or distilled water and Freund's adjuvant (FCA).

In vivo test system

Test animals

Species:

guinea pig

Strain:

Dunkin-Hartley

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Females nulliparous and non-pregnant: Not specified
- Weight at study initiation: 264 - 329 g
- Housing: Macrolon, type IV cages. 5 animals per cage.
- Diet: Ad libitum
- Water : Ad libitum, tap water; about 2 g of ascorbic acid per 10 L water was added to the drinking water twice a week.
- Acclimation period: At least 7 Days

ENVIRONMENTAL CONDITIONS
- Temperature: 20 - 24 °C
- Humidity: 30 - 70 %
- Photoperiod: 12 hours light (6.00 - 18.00 hours) / 12 hours darkness (18.00 - 6.00 hours)

Study design: in vivo (non-LLNA)

Induction

Induction 1

Route:

intradermal

Vehicle:

water

Concentration / amount:

10 % w/w in paraffin oil/aqua dest. (1:1), FCA/ aqua dest (1:1)

Day(s)/duration:

Treatment on Day 1

Adequacy of induction:

highest concentration used causing mild-to-moderate skin irritation and well-tolerated systemically

Induction 2

Route:

other: Percutaneous, occlusive

Vehicle:

water

Concentration / amount:

50 % w/w (about 0.3 g)

Day(s)/duration:

Treatment 7 Days after indradermal induction for 48 hours

Adequacy of induction:

highest concentration used causing mild-to-moderate skin irritation and well-tolerated systemically

Challenge

Challenge 1

No.:

#1

Route:

other: percutaneous, occlusive

Vehicle:

water

Concentration / amount:

10 % w/w

Day(s)/duration:

Treatment 14 days after percutaneous application

Adequacy of challenge:

highest non-irritant concentration

Challenge 2

No.:

#2

Route:

other: percutaneous, occlusive

Vehicle:

water

Concentration / amount:

10 % w/w

Day(s)/duration:

One week after first challenge

Adequacy of challenge:

highest non-irritant concentration

No. of animals per dose:

20 animals per test group, 10 animals per control group

Details on study design:

PRETESTS:
2 x 2 cm filter paper strips were applied to the skin of the flanks under an occlusive dressing. In the case of liquids the test filter paper strip is soaked in the test material formulation; in the case of solid substances the paper strip is coated with an approx. 0.5 mm thick layer of the test material formulation; thus, the animals were exposed to about 0.15 g of the test material formulation. Exposure period was 24 Hours, there were four test animals per concentration and there were readings 24, 48 and 72 hours after the beginning of application.

In the pretest, with percutaneous occlusive application, a 25 % aqueous formulation of the test material was found to be the minimum irritant concentration and a 25 % aqueous test substance formulation the maximum non-irritant con­centration. Since in an initial test with a challenge with 25 % aqueous test material concentration, unclear test results were obtained (skin reactions in control and test animals), the concentration of the challenge was reduced to 10 % in the present investigation.

MAIN STUDY
A. INDUCTION EXPOSURE
- Intradermal induction: 6 intradermal injections in groups of two per animal
- Exposure period: 48 Hours
- Test groups: (A) Front row: 2 injections each of 0.1 mL Freund's adjuvant without test material emulsified with water in a ratio of 1:1. (B) Middle row: 2 injections each of 0.1 mL of the test material formulation. (C) Back row: 2 injections each of 0.1 mL Freund's adjuvant / water (1:1) with test material
- Control group: The animals were given the same injections but without the test material, only with the formulating agent
- Site: Shoulder
- Readings: 24 hours after the beginning of application

- Percutaneous induction: 0.3 g of test material formulation was applied by means of 2 x 4 cm filter strip to the skin of the shoulder under an occlusive dressing.
- Exposure period: 48 hours
- Control groups: Control animals were not treated since the distilled water used as a formulating agent was not expected to influence the result of the study
- Site: Shoulder
- Readings: 48 hours after the beginning of application

B. CHALLENGE EXPOSURE
- Challenge 1: 0.15 g of test material formulation was applied by means of 2 x 2 cm filter strip to the skin of the flank under an occlusive dressing. Test group and control group one received treatment with test material formulation (control without test material), control group remained untreated.
- Challenge 2: Amount applied and method of application was the same as challenge one. Test group and both control groups one and two received test material formulation (controls without test material)
- Days of challenge: Challenge 1 was 19 days after intradermal induction, challenge 2 began 26 days after intradermal induction.
- Exposure period: 24 Hours
- Site: intact clipped flanks
- Concentrations: 10 % (w/w) of test material in aqua dest.
- Readings: 24, 48 and 72 hours after the beginning of application

OTHER:
- Preparation of animals: Clipping of the test animals, if required, was completed 3 to 5 hours before each reading and before each test material application at the appropriate application sites.
- Clinical examinations: No detailed examinations; a check for sick animals and for those showing deteriorated general state each workday.
- Bodyweight: Animals were weighed before each test material application and before the end of the study
- Scoring:
Erythema and eschar formation:
No erythema = 0
Very slight erythema (barely perceptible) = 1
Well-defined erythema = 2
Moderate to severe erythema = 3
Severe erythema (beet redness) to slight eschar formation (injuries in depth) = 4

Oedema formation
No oedema = 0
Very slight oedema (barely perceptible) = 1
Slight oedema (edges of area well defined by definite raising) = 2
Moderate oedema (raised approximately 1 mm) = 3
Severe oedema (raised more than 1 mm and extending beyond the area of exposure) = 4

Challenge controls:

A formulating agent was used that was not expected to influence the result of the test.

Positive control substance(s):

no

Results and discussion

In vivo (non-LLNA)

Results

Results 1

Reading:

1st reading

Hours after challenge:

48

Group:

negative control

Dose level:

10 % w/w in aqua dest.

No. with + reactions:

0

Total no. in group:

10

Remarks on result:

no indication of skin sensitisation

Results 2

Key result

Reading:

1st reading

Hours after challenge:

48

Group:

test chemical

Dose level:

10 % w/w in aqua dest.

No. with + reactions:

3

Total no. in group:

19

Clinical observations:

Very slight erythema, and very slight edema

Remarks on result:

positive indication of skin sensitisation

Results 3

Reading:

2nd reading

Hours after challenge:

72

Group:

negative control

Dose level:

10 % in aqua dest

No. with + reactions:

8

Total no. in group:

10

Clinical observations:

Very slight erythema, thin scab-like layers

Remarks on result:

positive indication of skin sensitisation

Results 4

Key result

Reading:

2nd reading

Hours after challenge:

72

Group:

test chemical

Dose level:

10 % w/w in aqua dest.

No. with + reactions:

15

Total no. in group:

19

Clinical observations:

Very slight erythema, thin scab-like layers

Remarks on result:

positive indication of skin sensitisation

Results 5

Reading:

rechallenge

Hours after challenge:

48

Group:

negative control

Dose level:

10 % in aqua dest.

No. with + reactions:

3

Total no. in group:

20

Clinical observations:

Very slight erythema

Remarks on result:

positive indication of skin sensitisation

Results 6

Key result

Reading:

rechallenge

Hours after challenge:

48

Group:

test chemical

Dose level:

10 % w/w in aqua dest.

No. with + reactions:

14

Total no. in group:

19

Clinical observations:

Very slight erythema, and very slight edema

Remarks on result:

positive indication of skin sensitisation

Results 7

Reading:

rechallenge

Hours after challenge:

72

Group:

negative control

Dose level:

10 % w/w aqua dest

No. with + reactions:

13

Total no. in group:

20

Clinical observations:

Very slight erythema, thin scab-like layers

Remarks on result:

positive indication of skin sensitisation

Results 8

Key result

Reading:

rechallenge

Hours after challenge:

72

Group:

test chemical

Dose level:

10 % w/w aqua dest

No. with + reactions:

17

Total no. in group:

19

Clinical observations:

Very slight erythema, and very slight edema, thin scab-like layers

Remarks on result:

positive indication of skin sensitisation

Any other information on results incl. tables

The Number of Animals with Skin Findings in Challenge Trials

	1st challenge		2nd challenge
	10 % in aqua dest.
	48 h after application	72 h after application	48 h after application	72 h after application
Control group 1	0/10	8/10	3/10	6/10
Control group 2	untreated		0/10	7/10
Test group*	3/19	15/19	14/19	17/19

 

x/y: Number of skin changes/number of guinea pigs tested

*1/20 animals died from pneumonia 20 days after the intradermal injection

Applicant's summary and conclusion

Interpretation of results:

other: Not classified according to EU criteria

Conclusions:

Under the conditions of this study, the skin sensitising potential of the test material is inconclusive due to the high percentage of control animals that exhibit the same reactions as the test animals.

Executive summary:

The sensitising potential of the test material was investigated similar to OECD Test Guideline 406 and in accordance with GLP.
20 female guinea pigs were initially subjected to an intradermal induction, where they each received 6 injections in groups of two into the shoulder. Two injections contained 0.1 mL FCA without test material emulsified with water in a ratio 1:1, two injections contained 1 mL of the test material formulation (10 % (w/w) in distilled water), and finally two injections contained 0.1 mL FCA in water (1:1) with test material. After intradermal induction, distinct erythema and oedema were observed at the injection sites of the test animals and also in the case of the control animals that only received Freund's adjuvant or paraffin oil and aqua dest. (1:1) without test material; 11 test animals had necrotic skin changes. Percutaneous induction was carried out a week later, where 50 % w/w test material in distilled water was added to the same area of skin via a filter paper strip. The site was exposed for 48 hours. Percutaneous induction was only carried out in the case of the guinea pigs of the experiment group, incrustation being observed in addition to distinct erythema and oedema. No application was made to the control animals, since, with aqua dest., a vehicle was used that was not expected to influence the result of the test.
Two challenges were then undertaken, with the first beginning 19 days after the intradermal induction. The test material was applied to the clipped flank of the animals by percutaneous application (conc. 10 % w/w in aqua dest.), for 24 hours. In contrast to the percutaneous induction, the skin findings observed in the two challenges are almost without exception merely very slight, scarcely perceptible reactions: erythema and thin scab-like layers and in the 2nd challenge also isolated cases of oedema were observed.
At the readings after 48 hours the number of animals with skin findings in the test group is appreciably higher than that in control group 1. However, as a result of evidently delayed reactions, the ratio of guinea pigs with skin changes to the number of animals used is in the same range in the control groups as in the test group at the readings after 72 hours.
Under the conditions of this study, the skin sensitising potential of the test material is inconclusive due to the high percentage of control animals that exhibit the same reactions as the test animals.