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Description of key information

The LD50 (oral, rat) value derived from the key-study was ca. 970 mg/kg bw. 

Key value for chemical safety assessment

Acute toxicity: via oral route

Link to relevant study records
Reference
Endpoint:
acute toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Study period:
January 1956
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Study was performed prior to the implementation of OECD Guidelines and GLP, but is in compliance with the principles described in OECD Guideline 401.
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 401 (Acute Oral Toxicity)
Deviations:
not applicable
Principles of method if other than guideline:
Study was performed prior to the implementation of OECD Guidelines and GLP, but is in compliance with the principles described in OECD Guideline 401.
GLP compliance:
no
Remarks:
test predated GLP
Test type:
standard acute method
Limit test:
no
Species:
rat
Strain:
not specified
Sex:
not specified
Details on test animals or test system and environmental conditions:
Young adult laboratory rats were purchased from a breeder. The source and strain of the animals were not documented.
Route of administration:
oral: gavage
Vehicle:
water
Details on oral exposure:
Concentration in vehicle: 10%
Doses:
500, 700, 1000, 1260, 2000, 4000, 5000 mg/kg bw
No. of animals per sex per dose:
(Dose in mg/kg bw : no of animals):
5000 : 1
4000 : 1
2000 : 5
1260 : 5
1000 : 5
700 : 5
500 : 5
Control animals:
no
Details on study design:
In principle, the methods described in OECD Guideline 401 were used.
Young adult laboratory rats were purchased from a breeder and the source and strain of the animals were not specified.
Groups of up to 5 rats and dose were treated simultaneously by gavage with preparations of the test substance in a suitable vehicle.
The concentrations of these preparations were usually adjusted to achieve comparable volumes (i.e. 10 ml) per kg body weight.
Group-wise documentation of clinical signs was performed over the 7 day study period. Body weight was determined before
the start of the study only, as it was needed for determination of dose. The clinical signs and findings were reported in summary form.

Statistics:
On the basis of the observed lethality, the LD50 value was determined using a graphical evaluation of the dose
response curve on probability paper.
Sex:
not specified
Dose descriptor:
LD50
Effect level:
ca. 970 mg/kg bw
Mortality:
All animals died when tested with 1200 mg/kg bw and above. 2/5 animals died at 1000 mg/kg bw and
1/5 rats were dead at 700 mg/kg bw, while all 5 rats survived 500 mg/kg bw. All animals died within 1 day after application.

Dose in mg/kg bw : no of animals that died/total no of animals:
5000 : 1/1
4000 : 1/1
2000 : 5/5
1260 : 4/5
1000 : 3/5
700 : 2/5
500 : 0/ 5
Clinical signs:
other: During acute toxicity studies signs observed in rats included convulsions, disequilibria, lateral posture, death within one day . Apathy, minor disequilibria, and accelerated respiration was noted in survivors.
Gross pathology:
No data
Executive summary:

In a non-guideline acute oral toxicity study the LD50 in rats was determined to be 970 mg/kg bw.

The symptoms were described as convulsions and disequilibria with lateral posture.

Deaths occurred within one day. Apathy and accelerated respiration was noted in survivors.

Endpoint conclusion
Endpoint conclusion:
adverse effect observed
Dose descriptor:
LD50
Value:
970 mg/kg bw

Acute toxicity: via inhalation route

Endpoint conclusion
Endpoint conclusion:
no study available

Acute toxicity: via dermal route

Endpoint conclusion
Endpoint conclusion:
no study available

Additional information

In an acute oral toxicity study the LD50 in rats was determined to be 970 mg/kg bw (BASF AG, 1956a). The symptoms were described as convulsions and disequilibria with lateral posture. Deaths occurred within one day. Apathy and accelerated respiration was noted in survivors. There is no difference in toxicity between this test with high purity imidazole when compared to the test with 95% imidazole (LD50 rat 960 mg/kg bw) which was performed under the same test conditions (BASF AG, 1956b).

Justification for classification or non-classification

The LD50 (oral, rat) value derived from the key-study was ca. 970 mg/kg bw. An acute dermal and inhalation toxicity study has not been performed, because imidazole is corrosive to the skin. Based on the available data imidazole is classified as follows: Acute toxicity Category 4, H302 "harmful if swallowed" (Regulation 1272/2008/EC).

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