α-n-butyl-α-(4-chlorophenyl)-1H-1,2,4-triazole-1-propanenitrile

Endpoint summary

Description of key information

Two in vivo studies are available addressing the effects of myclobutanil on rabbit skin. In both studies myclobutanil showed no skin irritation.

Two in vivo studies are available for effects on the eye. In the first study moderate eye irritation in the rabbit was observed. In the second study, vascularisation was evident at the end of study in one rabbit and a hazy yellow stained cornea in another rabbit. 

Key value for chemical safety assessment

Skin irritation / corrosion

Link to relevant study records

Reference

Endpoint:

skin irritation: in vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2005-06-24 to 2005-07-02

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method B.4 (Acute Toxicity: Dermal Irritation / Corrosion)

Version / remarks:

2004

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.2500 (Acute Dermal Irritation)

Version / remarks:

1998

Deviations:

no

Qualifier:

according to guideline

Guideline:

OECD Guideline 404 (Acute Dermal Irritation / Corrosion)

Version / remarks:

202

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Species:

rabbit

Strain:

New Zealand White

Remarks:

Albino

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Robinson Services, Inc. Clemmons, NC
- Age at study initiation: Young adult
- Weight at study initiation: not given in the report
- Housing: The animals were singly 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: Purina Certified High Fiber Rabbit Diet
- Water: Filtered tap water was supplied ad libitum by an automatic water dispensing system.
- Acclimation period: 7 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19-22 °C
- Humidity (%): 69-70%RH
- Photoperiod (hrs dark / hrs light): 12-hour light/dark cycle

Type of coverage:

semiocclusive

Preparation of test site:

clipped

Vehicle:

other: distilled water

Controls:

no

Amount / concentration applied:

0.5 g of the test item (0.77 g of the test mixture) was placed on a 1-inch x 1-inch, 4-ply gauze pad and applied on each animal. The pad and entire trunk of each animal were then wrapped with semi-occlusive 3-inch Micropore tape to avoid dislocation of the pad.

Duration of treatment / exposure:

4 hours

Observation period:

Individual dose sites were scored at approximately 30-60 minutes, 24, 48, and 72 hours after patch removal.

Number of animals:

3 (1 Male and 2 Females)

Details on study design:

TEST SITE
- Area of exposure: 6-cm^2 intact dose site on each animal
- Type of wrap if used: 3-inch Micropore tape

REMOVAL OF TEST SUBSTANCE
- Washing (if done): The test sites were gently cleansed of any residual test substance
- Time after start of exposure: 4 hours after exposure

OBSERVATION TIME POINTS
approximately 30-60 minutes, 24, 48, and 72 hours after patch removal

SCORING SYSTEM:
Individual dose sites were scored according to the Draize scoring system (see Table 3 below)

Irritation parameter:

erythema score

Basis:

animal #3

Time point:

24 h

Score:

1

Max. score:

4

Reversibility:

fully reversible within: 24 hours

Irritation parameter:

erythema score

Basis:

animal #2

Time point:

24 h

Score:

0

Max. score:

4

Reversibility:

other: not applicable

Irritation parameter:

erythema score

Basis:

animal #1

Time point:

24 h

Score:

1

Max. score:

4

Reversibility:

fully reversible within: 72 hours

Irritation parameter:

erythema score

Basis:

animal #3

Time point:

48 h

Score:

0

Max. score:

4

Reversibility:

other: not applicable

Irritation parameter:

erythema score

Basis:

animal #2

Time point:

48 h

Score:

0

Max. score:

4

Reversibility:

other: not applicable

Irritation parameter:

erythema score

Basis:

animal #1

Time point:

48 h

Score:

1

Max. score:

4

Reversibility:

fully reversible within: 72 hours

Irritation parameter:

erythema score

Basis:

mean

Time point:

72 h

Score:

0

Max. score:

4

Remarks on result:

no indication of irritation

Irritation parameter:

edema score

Basis:

mean

Time point:

24/48/72 h

Score:

0

Max. score:

4

Remarks on result:

no indication of irritation

Irritant / corrosive response data:

There was no edema observed at any treated site during this study. One hour after patch removal, all
three treated sites exhibited very slight erythema. The overall incidence and severity of irritation
decreased thereafter. All animals were free of dermal irritation by 72 hours.

Other effects:

All animals appeared active and healthy during the study.

Individual skin irritation scores are presented in Table 1. A summary of primary skin irritation scores is presented in Table 2. 

Interpretation of results:

GHS criteria not met

Conclusions:

A primary skin irritation test was conducted with Myclobutanil according to OECD/ EC guidelines and GLP principles. Under the conditions of this study, Myclobutanil caused very slight erythema, which cleared by 72 hours.

Executive summary:

A primary skin irritation test was conducted with New Zealand albino rabbits to determine the potential for Myclobutanil to produce irritation after a single topical application. Under the conditions of this study, the test substance caused very slight erythema, which cleared by 72 hours. Five-tenths of a gram of the test substance was moistened with distilled water and applied to the skin of three healthy rabbits for 4 hours. Following exposure, dermal irritation was evaluated by the method of Draize et al. There was no edema observed at any treated site during this study. One hour after patch removal, all three treated sites exhibited very slight erythema. The overall incidence and severity of irritation (maximum score 1) decreased thereafter. All animals were free of dermal irritation by 72 hours.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Eye irritation

Link to relevant study records

Reference

Reference 1

Endpoint:

eye irritation: in vivo

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

29-May-1984 to 19-June-1984

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 405 (Acute Eye Irritation / Corrosion)

Principles of method if other than guideline:

0.1 g of the ground amber solid test substance was applied to the corneal surface of 6 rabbits. Another 3 rabbits were treated, the eyes of these rabbits were irrigated with water for approximately 60 seconds starting 20-20 seconds after dosing. The eyelids were held open momentarily after dosing and then released gently to allow the animal to blink freely. The treated eyes were scored according to Draize's Procedure at 24, 48 and 72 hours after instillation, and at day 7, 14 and 21.

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Crude myclobutanil; 95.7% purity

Species:

rabbit

Strain:

New Zealand White

Remarks:

Albino

Details on test animals or tissues and environmental conditions:

TEST ANIMALS
- Source: Hazleton Dutchland. Denver. PA.
- Age at study initiation: Young adult
- Weight at study initiation: approximately 2.0 - 3.5 kg
- Housing: Rabbits were housed individually in stainless steel cages
- Diet: Purina Laboratory Rabbit Chow
- Water: Drinking quality water was available ad libitum either by an automatic watering system or by water bottles.
- Acclimation period: 6 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): not specified
- Humidity (%): not specified
- Photoperiod (hrs dark / hrs light): 12-hr light/dark

Vehicle:

unchanged (no vehicle)

Amount / concentration applied:

0.1g of the ground amber solid test substance was applied to the corneal surface

Observation period (in vivo):

The treated eyes were scored for signs of eye irritation at 24, 48 and 72 hours and at 7, 14 and 21 days after dose application.

Number of animals or in vitro replicates:

6 males (no washing after instillation);
3 males (eyes were rinsed with water 20-30 seconds after instillation)

Details on study design:

REMOVAL OF TEST SUBSTANCE
- Washing: For 3 of these rabbits, the treated eyes were irrigated with water for approximately 60 seconds. The treated eyes of the rest of the rabbits were remained unwashed.
- Time after start of exposure: 20-30 seconds after dosing

SCORING SYSTEM: The severity of the ocular effects were scored according to the system of Draize (J. Pharmacol, Exp. Therap. 82, 377-390, 1944).

Irritation parameter:

chemosis score

Basis:

mean

Time point:

24/48/72 h

Score:

0

Max. score:

0

Remarks on result:

not measured/tested

Irritation parameter:

conjunctivae score

Basis:

mean

Time point:

24/48/72 h

Score:

5

Max. score:

20

Reversibility:

fully reversible within: 14 days

Remarks on result:

no indication of irritation

Irritation parameter:

iris score

Basis:

mean

Time point:

24/48/72 h

Score:

0.6

Max. score:

10

Reversibility:

fully reversible within: 48 hours

Remarks on result:

no indication of irritation

Irritation parameter:

cornea opacity score

Basis:

mean

Time point:

24/48/72 h

Score:

7.8

Max. score:

80

Reversibility:

not reversible

Remarks on result:

probability of severe irritation

Remarks:

after 21 days: 1 animal with 1-2mm long blood vessel extended onto cornea; another animal: a 3 mm distinct hazy yellow area stain on the cornea

Irritant / corrosive response data:

For rabbits with unwashed eyes, slight to moderate irritation was observed in the cornea (6/6), iris (3/6) and conjunctiva (6/6) at 24 hours post-dosing. An uneven, pitted area was observed at the centre of the cornea of one rabbit with corneal and conjunctival effects. Test substance was noted to be present in the eyes of 3/6 rabbits, and around the eyes of the remaining 3 rabbits.
Irritation of reducing severity was present at 48 and 72 hours in the cornea (4/6 and 3/6, respectively) and conjunctiva (6/6 at both timepoints). Test substance was noted to be present around the eyes of the same 3 rabbits as before at 48 hours and in 1 rabbit at 72 hours.
At 7 days, irritation of the conjunctiva was still present in 2 rabbits. No irritation was observed at 14 and 21 days. However, a few blood vessels had extended into the cornea of one rabbit from Day 7 (one of the 3 rabbits with test material observed in the treated eye at 24 hrs) and, after dosing, a 3mm distinct hazy yellow stained area was seen on the cornea of another rabbit (one of the 3 rabbits with test material observed around the treated eye at 24, 48 and 72 hrs).

For rabbits with washed eyes, irritation was observed in all 3 animals in the conjunctiva at 24 hours, and only in 1 animal at 72 hours, respectively.

The results are included in Table 1 below.

Interpretation of results:

Category 1 (irreversible effects on the eye) based on GHS criteria

Conclusions:

The results of an in vivo eye irritancy test performed in rabbits indicated long-lasting effects on the eye for crude myclobutanil. Based on the duration of the ocular effects, the test substance was considered severely irritating to the eyes of rabbits (i.e., vascularization of the cornea was present at 21 days). Irrigating the exposed eyes with water for 60 seconds beginning 20 to 30 seconds after exposure prevented the corneal effects, decreased the conjunctival effects and shortened the recovery period.

Reference 2

Endpoint:

eye irritation: in vivo

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

24-June-2005 to 09-July-2005

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method B.5 (Acute Toxicity: Eye Irritation / Corrosion)

Version / remarks:

2004

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.2400 (Acute Eye Irritation)

Version / remarks:

1998

Deviations:

no

Qualifier:

according to guideline

Guideline:

OECD Guideline 405 (Acute Eye Irritation / Corrosion)

Version / remarks:

2002

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

99.7% purity

Species:

rabbit

Strain:

New Zealand White

Remarks:

Albino

Details on test animals or tissues and environmental conditions:

TEST ANIMALS
- Source: Robinson Services Inc., Clemmons, NC
- Age at study initiation: Young adult
- Housing: The animals were singly 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: Purina Certified High Fiber Rabbit Diet
- Water: Filtered tap water was supplied ad libitum by an automatic water dispensing system.
- Acclimation period: 7 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19-21°C
- Humidity (%): 54-69%RH
- Photoperiod (hrs dark / hrs light): 12-hour light/dark cycle

Vehicle:

unchanged (no vehicle)

Controls:

other:

Amount / concentration applied:

0.1 mL (0.04 grams of the ground test substance)

Duration of treatment / exposure:

Not applicable: treated eyes were not rinsed after exposure

Observation period (in vivo):

72 hours

Number of animals or in vitro replicates:

3 male rabbits

Details on study design:

SCORING SYSTEM: Ocular irritation was evaluated in accordance with Draize et al. (see Table 3 below)

TOOL USED TO ASSESS SCORE: A high-intensity white light (Mag Lite)

Irritation parameter:

chemosis score

Basis:

mean

Time point:

24/48/72 h

Score:

0.3

Max. score:

4

Reversibility:

fully reversible within: 48 hours

Irritation parameter:

iris score

Basis:

mean

Time point:

24/48/72 h

Score:

0.3

Max. score:

2

Reversibility:

fully reversible within: 48 hours

Irritation parameter:

cornea opacity score

Basis:

mean

Time point:

24/48/72 h

Score:

0.2

Max. score:

4

Reversibility:

fully reversible within: 48 hours

Irritation parameter:

conjunctivae score

Basis:

mean

Time point:

24/48/72 h

Score:

1

Max. score:

3

Reversibility:

fully reversible within: 72 hours

Irritant / corrosive response data:

One hour after test substance instillation, all three treated eyes exhibited iritis and conjunctivitis.
Corneal opacity was evident in two rabbits by 24 hours. The overall incidence and severity of irritation decreased thereafter. All animals were free of ocular irritation by 72 hours. Individual and mean eye irritation scores are presented in Table 1 and 2 respectively. 

Other effects:

All animals appeared active and healthy during the study. There were no signs of gross toxicity, adverse clinical signs, or abnormal behavior.

Interpretation of results:

GHS criteria not met

Conclusions:

A primary eye irritation test was conducted according to OECD/EC guidelines and GLP principles. Under the conditions of this study, Myclobutanil (99.7% purity) caused corneal opacity, iritis, and conjunctival irritation, which cleared by 72 hours.

Executive summary:

A primary eye irritation test was conducted according to OECD/EC guidelines and GLP principles. One-tenth of a milliliter (0.04 grams) of the ground test substance (99.7% purity) was instilled into the right eye of three healthy rabbits. The left eye remained untreated and served as a control. Ocular irritation was evaluated by the method of Draize et al. One hour after test substance instillation, all three treated eyes exhibited iritis and conjunctivitis. Corneal opacity was evident in two rabbits by 24 hours. The overall incidence and severity of irritation decreased thereafter. All animals were free of ocular irritation by 72 hours.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (irritating)

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

A primary skin irritation test was conducted with New Zealand albino rabbits to determine the potential for Myclobutanil to produce irritation after a single topical application. Under the conditions of this study, the test substance caused very slight erythema, which cleared by 72 hours. Five-tenths of a gram of the test substance was moistened with distilled water and applied to the skin of three healthy rabbits for 4 hours. Following exposure, dermal irritation was evaluated by the method of Draize et al. There was no edema observed at any treated site during this study. One hour after patch removal, all three treated sites exhibited very slight erythema. The overall incidence and severity of irritation (maximum score 1) decreased thereafter. All animals were free of dermal irritation by 72 hours.

 

A second study is available, in which Myclobutanil (0.5 mL) was applied to the skin of 6 male rabbits under a patch covered with an impervious cuff. After 4 hours exposure, the patches and cuffs were removed and the application sites were wiped gently. Erythema and edema were scored at 1 hour after removal, at 24 and 72 hours and after one week.  

At no time point adverse skin effects were noted, as a result is this test substance considered practically non-irritating to the skin of rabbits.

A primary eye irritation test was conducted according to OECD/EC guidelines and GLP principles. One-tenth of a milliliter (0.04 grams) of the ground test substance (99.7% purity) was instilled into the right eye of three healthy rabbits. The left eye remained untreated and served as a control. Ocular irritation was evaluated by the method of Draize et al. One hour after test substance instillation, all three treated eyes exhibited iritis and conjunctivitis. Corneal opacity was evident in two rabbits by 24 hours. The overall incidence and severity of irritation decreased thereafter. All animals were free of ocular irritation by 72 hours. Based on this study no classification for serious eye damage or serious eye irritation is warranted.

In a second study, 0.1 g of the ground amber solid test substance (crude myclobutanil, 85.7% purity) was applied to the corneal surface of 6 rabbits. Another 3 rabbits were treated, the eyes of these rabbits were irrigated with water for approximately 60 seconds starting 20-30 seconds after dosing. The eyelids were held open momentarily after dosing and then released gently to allow the animal to blink freely. The treated eyes were scored according to Draize's Procedure at 24, 48 and 72 hours after instillation, and at day 7, 14 and 21. The results of this in vivo eye irritancy test performed indicated long-lasting effects on the eye. Based on the duration of the ocular effects, the test substance was considered severely irritating to the eyes of rabbits (i.e., vascularization of the cornea was present at 21 days). Irrigating the exposed eyes with water for 60 seconds beginning 20 to 30 seconds after exposure prevented the corneal effects, decreased the conjunctival effects and shortened the recovery period.

The results of the study performed using crude myclobutanil indicate that classification as Eye Dam. Cat 1 is appropriate for this grade of material.  However, the results of the study performed with material of higher (99.7%) purity representative of the registered substance do not trigger CLP classification for serious eye damage or serious eye irritation.  The different results of the two studies indicate that the eye irritation is due to the presence of process impurities.  Nonetheless, myclobutanil has a harmonised CLP classification for serious eye irritation in Category 2.  While the available data indicate that this classification is not required, the classification cannot be removed without specific consultation and the submission of a separate CLH dossier.

Justification for classification or non-classification

Based on the available data it is concluded that Myclobutanil does not have to be classified for skin irritation or corrosion according to the Classification, Labelling and Packaging (CLP) Regulation ((EC) No 1272/2008).

A harmonised classification for Myclobutanil is available for serious eye irritation (Cat. 2, H319)).  The available data for high purity myclobutanil indicate that classification for serious eye irritation (Cat. 2) or serious eye damage (Cat. 1) is not required; however removal of the harmonised classification is beyond the scope of the REACH registration dossier.