1,2-dimethylimidazole

Endpoint summary

Description of key information

The oral LD50 was ca. 1300 mg/kg bw, the inhalation LC50 (after 4 h exposure) was > 3 mg/L and the dermal LD50 was > 200 mg/kg bw.

Key value for chemical safety assessment

Acute toxicity: via oral route

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

LD50

Value:

1 330 mg/kg bw

Acute toxicity: via inhalation route

Link to relevant study records

Reference

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Remarks:

Meets generally accepted scientific standards, well documented and acceptable for assessment

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 403 (Acute Inhalation Toxicity)

Version / remarks:

prior to the adoption of OECD403 in 1981

GLP compliance:

no

Test type:

standard acute method

Limit test:

no

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: SPF-Zucht, Firma MUS RATTUS, Brunnthal
- Weight at study initiation: 185 +/- 15 g
- Diet: Herilan MRH (Firma H. Eggersmann, Rinteln/Weser), ad libitum
- Water: ad libitum

Route of administration:

inhalation: aerosol

Type of inhalation exposure:

nose/head only

Vehicle:

air

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Aerosol generation: generated using a continuous infusion pump to lead the water/substance mixture (50%) through a two-fluid nozzle with compressed air
-Tubes in which the snout extends into an inhalation chamber for exposure

Analytical verification of test atmosphere concentrations:

yes

Duration of exposure:

4 h

Concentrations:

3.01 mg/l (analytical), 19.59 mg/l (nominal)
2.39 mg/l (analytical), 15.33 mg/l (nominal)

No. of animals per sex per dose:

10

Control animals:

yes

Details on study design:

- Duration of observation period following administration: 14 days
- Necropsy of survivors performed: yes
- Other examinations performed: clinical signs and body weight

Statistics:

The statistical analysis of the experiment was based on the binomial test by the computational center at BASF.

Sex:

male/female

Dose descriptor:

LC50

Effect level:

3 mg/L air

Based on:

test mat.

Exp. duration:

4 h

Sex:

male/female

Dose descriptor:

LC50

Effect level:

12 mg/L air

Based on:

test mat.

Exp. duration:

1 h

Remarks on result:

other: conversion of the 4-h LC50 according to the Haber-rule

Sex:

male

Dose descriptor:

LC50

Effect level:

3 mg/L air

Based on:

test mat.

Exp. duration:

4 h

Sex:

male

Dose descriptor:

LC50

Effect level:

12 mg/L air

Based on:

test mat.

Exp. duration:

1 h

Remarks on result:

other: conversion of the 4-h LC50 according to the Haber-rule

Sex:

female

Dose descriptor:

LC50

Effect level:

3 mg/L air

Based on:

test mat.

Exp. duration:

4 h

Sex:

female

Dose descriptor:

LC50

Effect level:

12 mg/L air

Based on:

test mat.

Exp. duration:

1 h

Remarks on result:

other: conversion of the 4-h LC50 according to the Haber-rule

Mortality:

No mortality occured

Clinical signs:

other: Watery, reddish eyes and nasal secretions. Shock manner or rapid breathing. Long-legged, tumbling movement. Scruffy look. Matted fur. Alopecia. 2 out of 20 male animals showed nose burns. On the day of necropsy symptoms were still recorded.

Body weight:

Slight differences in body weight gain were observed in the test groups compared to the control group.

Gross pathology:

No treatment related findings.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

discriminating conc.

Value:

300 mg/m³ air

Acute toxicity: via dermal route

Link to relevant study records

Reference

Endpoint:

acute toxicity: dermal

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Remarks:

Meets generally accepted scientific standards, well documented and acceptable for assessment

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 402 (Acute Dermal Toxicity)

Version / remarks:

prior to the adoption of OECD402 in 1981

GLP compliance:

no

Test type:

standard acute method

Limit test:

yes

Species:

rabbit

Strain:

Vienna White

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: M.GAUKLER (6050 Offenbach, Germany)
- Weight at study initiation: 2.9 kg
- Diet: Ssniff K, standard diet for rabbits and guinea pigs (Firma INTERMAST GMBH, Soest), ad libitum
- Water: ad libitum

Type of coverage:

occlusive

Vehicle:

water

Details on dermal exposure:

TEST SITE
15 to 24 hrs before treatment, dorsal and lateral parts of the body of the animals were shaved with an electric clipper exposing an area of approximatly 50 cm2

- Type of wrap if used: aluminium foil fixed with adhesive tape

REMOVAL OF TEST SUBSTANCE
- Washing: with warm water or a water/Lutrol mixture
- Time after start of exposure: 24 hours

TEST MATERIAL
- Concentration: 50 % solution

Duration of exposure:

24 hours

Doses:

200 mg/kg bw

No. of animals per sex per dose:

5

Control animals:

no

Details on study design:

- Duration of observation period following administration: 8 days
- Frequency of observations and weighing: after 1, 24 and 48 hours and on day 8
- Necropsy of survivors performed: yes
- Other examinations performed: clinical signs and local skin irritaion

Sex:

male/female

Dose descriptor:

LD50

Effect level:

> 200 mg/kg bw

Based on:

test mat.

Mortality:

None of the animals died during the observation period.

Clinical signs:

other: No abnormal observations were reported.

Gross pathology:

No abnormal observations were reported.

Other findings:

24 hours after application the animals show a mild primary skin irritation which remained consistent for almost 48 hours.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

discriminating dose

Value:

200 mg/kg bw

Additional information

Oral toxicity
In an oral toxicity study, comparable to OECD guideline 401, US-rats (5/sex/dose) were administered 1,2-dimethylimidazole at 200, 800, 1000, 1250 and 1600 mg/kg bw by single dose (gavage) followed by a 7-day observation period (1965, RL2). Clinical signs included partly/slight staggering, shaking, slight dyspnoea, mild cramps, trembling, apathy, rough coat, bloody crusted nose and eyes. Findings at necropsy showed stomach filled with test substance and bleeding of gastric mucosa. The LD50 was ca 1300 mg/kg bw.

Inhalation toxicity
In an inhalation toxicity study, comparable to OECD 403, Sprague-Dawley rats (10/sex/dose) were exposed (nose/head only) for 4 hours to 3.01 and 2.39 mg/L 1,2 -dimethylimidazole followed by a 14 day observation period (1979, RL2). No mortality occurred. Clinical signs included watery, reddish eyes and nasal secretions. Shock manner or rapid breathing. Long-legged, tumbling movement. Scruffy look. Matted fur. Alopecia. 2 out of 20 male animals showed nose burns. On the day of necropsy symptoms were still recorded. No abnormal findings at necropsy were observed. The LC50 was > 3 mg/L.
In another study, comparable to OECD 403, in which rats (3/sex-dose) were exposed for 8 hours to a saturated 1,2-dimethylimidazole atmosphere vapour at 20°C (0.9 mg/L) no deaths were observed during a 14-day observation period (1965, RL2). The LC50 was > 0.9 mg/L.

Dermal toxicity:
In an acute dermal toxicity study, similarly performed according to OECD guideline 402, Vienna white Rabbits (5/sex) were administered 1,2 -dimethylimidazole (200 mg/kg bw) (1979, RL2). 1,2-Dimethylimidazole was dissolved in distilled water and applied on the skin (skin area of approx 50 cm2) and covered in aluminium foil fixed with adhesive tape. The treated skin was washed after 24 hours and a 8 day observation period followed. No mortality was observed during this period resulting in a LD50 > 200 mg/kg bw.

Justification for classification or non-classification

As no mortality was observed in the acute inhalation toxicity study (LC50 > 3.01 mg/l) and acute dermal study (LD50 > 200 mg/kg bw), classification for acute inhalation and dermal toxicity is not needed.

Based on the available data, 1,2 -dimethylimidazole has to be classified for acute oral toxicity. According to the EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation (EC) No. 1272/2008, the classification is H302, Cat. 4, which is in accordance with Annex VI.