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Acute Toxicity: oral

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Administrative data

Endpoint:
acute toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Study period:
22nd February to 13th April 1994
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Study conducted in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of the relevant results. The study report was conclusive, done to a valid guideline and the study was conducted under GLP conditions.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1994
Report date:
1994

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to guideline
Guideline:
EU Method B.1 (Acute Toxicity (Oral))
Deviations:
no
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 401 (Acute Oral Toxicity)
Deviations:
not applicable
GLP compliance:
yes
Test type:
standard acute method
Limit test:
no

Test material

Constituent 1
Chemical structure
Reference substance name:
3,5-dimethylpyrazole
EC Number:
200-657-5
EC Name:
3,5-dimethylpyrazole
Cas Number:
67-51-6
Molecular formula:
C5H8N2
IUPAC Name:
3,5-dimethyl-1H-pyrazole
Test material form:
solid: particulate/powder
Remarks:
migrated information: powder
Details on test material:
Appearance: White crystalline powder.
Storage Conditions: Room temperature in the dark.
Date Received: 11th February 1994.

Test animals

Species:
rat
Strain:
Sprague-Dawley
Sex:
male/female
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: Harlan Olac Ltd., Bicester, Oxon, England.
- Age at study initiation: 4-7 weeks.
- Weight at study initiation: 96 to 119 g.
- Fasting period before study: Overnight prior to and approximately 4 hours after dosing.
- Housing: In treatment groups, up to 5 individuals of the same sex. In metal ages with wire mesh floors.
- Diet (e.g. ad libitum): Standard laboratory rodent diet, Biosure LAD 1, ad libitum except for fasting period.
- Water (e.g. ad libitum): Drinking water, ad libitum except for fasting period.
- Acclimation period: Minimum 7 days.
- Routine analysis was carried out on water and died.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): mean daily minimum and maximum 21 ºC and 22 ºC.
- Humidity (%): av. 47%.
- Air changes (per hr): 10 to 15 per hour.
- Photoperiod (hrs dark / hrs light): Artificial light between 0700 - 1900, in each 24 hour period

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
other: Methycellulose.
Details on oral exposure:
VEHICLE
- Concentration in vehicle: 1% w/v aqueous methylcellulose.

MAXIMUM DOSE VOLUME APPLIED: 10 ml/kg
Doses:
Preliminary Study - 500 mg/kg bw.
Main Test - Single dose of 1260, 1600 and 2000 mg/kg bw.
No. of animals per sex per dose:
Preliminary Study: 2 males and 2 females.
Main Study: 5 males and 5 females at 2000 mg/kg bw. 5 females only at 1600 and 1200 mg/kg bw as these were determined as the most sensitive sex.
Control animals:
no
Details on study design:
Preliminary Study:
- A single dose was administered.

Main Study:
- Males and females were initially exposed at 2000 mg/kg bw of the test material.
- Based on the response of the first dose, two further groups of female rats were dosed, to obtain a dose response curve and allow calculation of a lethal dose. A single dose was administered at 1260 and 1600 mg/kg bw.

Observations:
- Mortality, time of death was recorded.
- Clinical signs, observations were recorded soon after dosing and at frequent intervals on Day 1. Then for the remainder of the study observations were made twice daily. Nature and severity were recorded.
- Bodyweight, recorded on Days 1, 8 and 15 or at death. Individual weekly bodyweight changes and group mean bodyweights were calculated.
- Macroscopic examinations, necropsy was performed on Day 15. The cranial, abdominal and thoracic cavities were examined.
Statistics:
Acute median lethal oral dose in females was calcualted using the Finney (1971) method.

Results and discussion

Preliminary study:
Results indicated that the LD50 > 500 mg/kg bw in females.
Effect levels
Key result
Sex:
female
Dose descriptor:
LD50
Effect level:
1 717 mg/kg bw
Based on:
test mat.
95% CL:
1 360 - 2 269
Mortality:
Results from the preliminary study showed that the acutre lethal oral dose was greater than 500 mg/kg bw.
In the main study, all deaths occurred within the period ranging from 3 hours to 2 days post exposure.
The mortalities were as follows; two females at 1600 mg/kg bw and two males and four females at 2000 mg/kg bw.
Clinical signs:
Piloerection, abnormal body carriage (hunched posture), lethargy, decreased respiratory rate, partially closed eyelids, pallor of the extremities, unsteadiness and increased lacrimation, abnormal gait (waddling), increased salivation, walking on toes, prostration, collapsed state and cold body surfaces, were all noted in one or more dosed groups.
Body weight:
Slightly low bodyweight gains were recorded on Day 8 for one female in the 1260 mg/kg bw group and for three males and one female in the 2000 mg/kg bw group. However these rats did reach the anticipated bodyweight gain by Day 15.
Gross pathology:
A darkened appearance of the kidney cortex and spleen were observed in one female at 1600 mg/kg bw.
Thickening of the stomach walls and fluid contents in the stomach and intestines was observed in individuals at both 1600 and 2000 mg/kg bw.
Other findings:
- Females were more sensitive than males.
- Recovery of surviving rats, judged on external appearance, occurred by Day 3 in the 1260 mg/kg bw group, Day 4 in the 1600 mg/kg bw group and Day 5 for the 2000 mg/kg bw group.
- No abnormalities were recorded in microscopic examinations.

Any other information on results incl. tables

Table 1. Time and Number of Deaths During the Main Study

Sex Dose (mg/kg bw) Number of deaths in a group of 5 Day
1 2 3 to 15
Hours after dosing Observation
< 1/2 1 2 3 4 5 6 1st 2nd 1st 2nd
Male 2000 2               2      
Female 1260 0          
1600 2     1 1  
2000 4       1 1     1 1    

Applicant's summary and conclusion

Interpretation of results:
Category 4 based on GHS criteria
Conclusions:
The LD50 in female rats was determined, using the standard acute toxicity method, to be 1717 mg/kg bw.
Executive summary:

In a GLP compliant study performed in accordance with the standardised guideline EU Method B.1, the acute oral toxicity of the test material was determined in female Sprague-Dawley rats following the standard acute method. Male and female rats were exposed to the test material via oral gavage, females were found to be more sensitive and were used in further testing to determine the LD₅₀. Under the conditions of the test the LD₅₀ was determined to be 1717 mg/kg bw.

According to Regulation (EC) 1272/2008 the test material requires classification as Acute oral toxicity category 4 "H302: Harmful if swallowed" with the signal word "Warning".