picoxystrobin (ISO); methyl (2E)-3-methoxy-2-[2-({[6-(trifluoromethyl)pyridin-2-yl]oxy}methyl)phenyl]acrylate

Endpoint summary

Description of key information

Guinea pig. Not sensitising. OECD 406; Reliability = 1

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records

Reference

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:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 406 (Skin Sensitisation)

Deviations:

yes

Remarks:

Due to a technician error, Animal No. 3606 was inadvertently not scored at the 48-hour evaluation. Due to a negative result for sensitization potential, this deviation had no impact on the results of this study.

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.2600 (Skin Sensitisation)

Deviations:

yes

Remarks:

Due to a technician error, Animal No. 3606 was inadvertently not scored at the 48-hour evaluation. Due to a negative result for sensitization potential, this deviation had no impact on the results of this study.

Qualifier:

according to guideline

Guideline:

other: JMAFF 12-Nouan-8147, November 2000

Deviations:

yes

Remarks:

Due to a technician error, Animal No. 3606 was inadvertently not scored at the 48-hour evaluation. Due to a negative result for sensitization potential, this deviation had no impact on the results of this study.

GLP compliance:

yes

Type of study:

guinea pig maximisation test

Justification for non-LLNA method:

LLNA study was not performed since in vivo guinea pig data were already available for the test substance.

Species:

guinea pig

Strain:

Hartley

Remarks:

albino

Sex:

male

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Elm Hill Breeding Labs, Chelmsford, Massachusetts
- Age at study initiation: Young adult
- Weight at study initiation: 346-416 grams
- Housing: The animals were group housed in suspended stainless steel caging with mesh floors. Litter paper was placed beneath the cage and was changed at least three times per week.
- Diet: Pelleted Purina Guinea Pig Chow #5025
- Water: Filtered tap water was supplied ad libitum by automatic water dispensing system.
- Acclimation period: 7-29 days

ENVIRONMENTAL CONDITIONS
- Temperature: 19-23°C
- Humidity: 36-62%
- Photoperiod (hrs dark / hrs light): 12 hour light/dark cycle

Route:

intradermal

Vehicle:

other: Mineral oil

Concentration / amount:

The test animals received six intradermal injections (0.1 mL each) in the shaved suprascapular region as follows:
50% v/v mixture of Complete Freund's Adjuvant in distilled water; 5% w/w mixture of test substance in mineral oil; 5% w/w mixture of test substance in 50% Complete Freund's Adjuvant in distilled water

Day(s)/duration:

24 and 48 hours

Route:

intradermal

Vehicle:

other: Mineral oil

Concentration / amount:

The test vehicle control group animals received six intradermal injections (0.1 mL each) in the clipped suprascapular region as follows:
50% v/v mixture of Complete Freund's Adjuvant in distilled water; 100% mineral oil; 50% w/w mixture of mineral oil in 50% Complete Freund's Adjuvant in distilled water

Day(s)/duration:

24 and 48 hours

Route:

epicutaneous, semiocclusive

Vehicle:

other: mineral oil

Concentration / amount:

0.5 gms of 75% w/w

Day(s)/duration:

48 hours

No.:

#1

Route:

epicutaneous, occlusive

Vehicle:

other: Mineral oil

Concentration / amount:

0.5 mL of 38 and 13% w/w

Day(s)/duration:

24 hours

No. of animals per dose:

Preliminary Irritation Testing: 12
Test Group: 20
Test Vehicle Control Group: 10

Details on study design:

RANGE FINDING TESTS:
- Preliminary Intradermal Injection: Prior to the induction phase, a group of four animals was used to determine the concentration of the test substance which produced faint to moderate irritation via intradermal injection. Each guinea pig received six intradermal injections (0.1 mL each); three concentrations (1, 3, and 5%) of the test substance in mineral oil and the same concentrations in an emulsion of Complete Freund's Adjuvant. Approximately 24 and 48 hours after the injections, each site was evaluated for local reactions (erythema).
- Preliminary Topical: Prior to the topical induction, a group of four animals was used to determine the irritation potential of the test substance to be used during the topical induction. The test substance was mixed with mineral oil to yield w/w concentrations of 75% and 56%. Each concentration (0.5 g or mL) was applied to a 2 cm x 4 cm, 2-ply gauze patch and placed on one of the two test sites. After a 48 hour exposure period, the patches were removed and the test sites were gently cleansed of any residual test substance. One hour after patch removal, readings were made of local reactions (erythema).
Highest Non-irritating Concentration (HNIC): Prior to the challenge phase, a group of four animals was used to determine the highest non-irritating concentration. The fur was removed by clipping the flanks of each guinea pig. The test substance mixed with mineral oil to yield w/w concentrations of 75%, 56%, 38% and 19%. Each concentration (0.5 g or mL) was applied to an occlusive 25 mm Hill Top Chamber and applied to the appropriate test site. The sites were wrapped with non-allergenic Durapore™ adhesive tape. After 24 hours of exposure, the chambers were removed and the test sites were gently cleansed of any residual test substance. Approximately 24 and 48 hours after patch removal, each site was evaluated for local reactions (erythema).
Based on these findings, the concentration which produced faint to moderate irritation (1-2) selected for the intradermal induction was a 5% w/w mixture in mineral oil. That which produced moderate irritation (2) selected for the topical induction was a 75% w/w mixture in mineral oil. The HNIC selected for the challenge phase was a 38% w/w mixture in mineral oil.

MAIN STUDY
A. INDUCTION EXPOSURE
- No. of exposures: 6
- Exposure period: 24 and 48 hours
- Test groups: 3
- Control group: 3
- Site: Suprascapular region
- Frequency of applications: Once in intradermal phase and once in topical phase
- Duration: 7 days

B. CHALLENGE EXPOSURE
- No. of exposures: 3
- Day of challenge: On Day 21
- Exposure period: 24 hours
- Test groups: 3
- Control group: 1
- Site: Right and left flank
- Concentrations: 13 and 38% w/w mixture in mineral oil
- Evaluation (hr after challenge): Approximately 24 and 48 hours after patch removal

Positive control substance(s):

yes

Remarks:

alpha-Hexylcinnamaldehyde

Positive control results:

Topical Induction Phase
Historical Positive Control Animals (100% HCA): Faint to moderate erythema (1-2) was noted at all positive control sites following the topical induction application.

Challenge Phase
Historical Positive Control Animals (75% w/w mixture of HCA in mineral oil): All ten positive control animals exhibited signs of a sensitization response (faint to moderate erythema [1-2]) 24 hours after challenge patch removal. Similar indications persisted at nine sites through 48 hours.

Key result

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

38% w/w

No. with + reactions:

0

Total no. in group:

20

Clinical observations:

None

Key result

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

13% w/w

No. with + reactions:

0

Total no. in group:

20

Clinical observations:

None

Key result

Reading:

2nd reading

Hours after challenge:

48

Group:

test chemical

Dose level:

38 % w/w

No. with + reactions:

0

Total no. in group:

20

Clinical observations:

None

Key result

Reading:

2nd reading

Hours after challenge:

48

Group:

test chemical

Dose level:

13% w/w

No. with + reactions:

0

Total no. in group:

20

Clinical observations:

None

Key result

Reading:

1st reading

Hours after challenge:

24

Group:

negative control

Dose level:

0% w/v

No. with + reactions:

0

Total no. in group:

10

Clinical observations:

None

Concentration	Incidence with Skin Reactions
	Test Animals		Test Vehicle Control Animals
	24 h	48 h	24 h	48 h
38% w/w in mineral oil	0/20	0/20	0/10	0/10
13% w/w in mineral oil	0/20	0/20	0/10	0/10
Mineral oil	0/20	0/20	0/10	0/10

Concentration	Severity
	Test Animals		Test Vehicle Control Animals
	24 h	48 h	24 h	48 h
38% w/w in mineral oil	0.25	0.20	0.20	0.15
13% w/w in mineral oil	0.23	0.13	0.15	0.05
Mineral oil	0.00	0.00	0.00	0.00

Interpretation of results:

GHS criteria not met

Conclusions:

The test substance is considered not to be a contact skin sensitizer.

Executive summary:

A Magnusson-Kligman maximization test was conducted with guinea pigs to determine the potential for the test substance to invoke dermal skin sensitization reactions.

The study was conducted using four stages; preliminary irritation screens, a two-stage induction phase, and a challenge phase as described below.

Preliminary irritation testing was performed on 12 animals to determine appropriate concentrations of the test substance that could be used for both intradermal and topical induction as well as topical challenge.

The first induction phase involved six intradermal injections into the suprascapular area of each of 20 guinea pigs. These doses were comprised of pairs of injections of the test substance in mineral oil, the test substance combined with Complete Freund's Adjuvant, as well as Adjuvant alone. A test vehicle control group (ten animals) was maintained under the same environmental conditions and received injections of mineral oil, mineral oil combined with Complete Freund's Adjuvant, as well as Adjuvant alone. Approximately 24 and 48 hours after the injections, all sites were evaluated for an irritation response (erythema).

Approximately one week later, the second phase of induction was conducted. The test substance (test group) or mineral oil (test vehicle control group) was applied topically for a period of 48 hours to the area encompassing the intradermal injection sites. Approximately one hour after the topical induction patches were removed, all animals were scored for erythema.

Approximately two weeks later, a primary challenge consisting of three occluded applications was conducted on each animal. One Hill Top Chamber containing 0.5 mL of mineral oil was applied to a naive site on the right flank of each animal. The remaining two Hill Top Chambers containing 0.5 mL of the HNIC (Highest Non-Irritating Concentration, determined in the preliminary irritation screen to be a 38% w/w mixture in mineral oil) of the test substance and 0.5 mL of a 33% dilution of the HNIC (13% w/w mixture in mineral oil) were positioned on two naive sites on the left front and rear flank, respectively, for approximately 24 hours. The test vehicle control group was also treated with the test substance and test vehicle (as described above) at challenge. Approximately 24 and 48 hours after challenge patch removal, all animals were scored for a sensitization response (erythema)

Based on the results of this study, the test substance is considered not to be a contact skin sensitizer.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

The dermal sensitization potential of the test substance was evaluated in guinea pigs by the Magnusson and Kligman maximisation method in male Hartley albino guinea pigs. The percentage of sensitisation at 24 and/or 48 hours for the test article animals challenged with 38% or 13% of test substance was 0%. Appropriate historical control data using HCA demonstrated a positive response. Under the conditions of this study, the test substance did not possess skin sensitising potential.

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

There was no evidence of dermal sensitisation in guinea pigs. The substance does not need to be classified for skin sensitisation according to EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation (EC) No. 1272/2008.