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Acute Toxicity: oral

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acute toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Study period:
11 July 2001 - 25 September 2001
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference Type:
study report
Report date:

Materials and methods

Test guidelineopen allclose all
according to guideline
OECD Guideline 401 (Acute Oral Toxicity)
according to guideline
EPA OPPTS 870.1100 (Acute Oral Toxicity)
according to guideline
other: JMAFF Acute Oral Toxicity Study, 2000
according to guideline
EU Method B.1 (Acute Toxicity (Oral))
GLP compliance:
Test type:
standard acute method
Limit test:

Test material

Constituent 1
Chemical structure
Reference substance name:
EC Number:
EC Name:
Cas Number:
Molecular formula:

Test animals

Fischer 344
Details on test animals or test system and environmental conditions:
Fischer 344 rats obtained from Charles River Laboratories Inc. (Raleigh, North Carolina) and weighing 102-245 grams at study start were used for this study. Rats were born on May 7, 2001 or June 11, 2001. The rats were dosed on July 17, 18, 24, 31, or August 2, 8, 2001 and were sent to necropsy on August 1, 7, 14, 16, or 22, 2001. Animal care facilities are fully accredited by the Association for Assessment and Accreditation of Laboratory Animal Care International. Upon arrival at the laboratory, the rats were examined for health status by the laboratory veterinarian. Animals were housed two or three per cage in stainless steel cages in rooms that were designed to maintain adequate environmental conditions concerning temperature, humidity, photocycle, and air exchanges. The relative humidity and room temperature were maintained within a range of 40-70% and 22 ± 3 °C, respectively. A 12-hour light/dark photocycle was maintained for all animal rooms with lights on at 6:00 a.m. and off at 6:00 p.m. Room air was exchanged approximately 12-15 times/hour, and the water lines automatically bled every six hours.
Animals were provided LabDiet Certified Rodent Diet #5002 (PMI Nutrition International, St. Louis, Missouri) in pelleted form. Feed and municipal water were provided ad libitum. Analysis of the feed was performed by PMI Nutrition International to confirm the nutritional adequacy of the diet and to quantify the levels of selected contaminants. Drinking water obtained from the municipal water source was periodically analyzed for chemical parameters and biological contaminants by the municipal water department. In addition, specific analyses for chemical contaminants were conducted at periodic intervals by an independent testing facility. Copies of these analyses are maintained at Toxicology & Environmental Research and Consulting, The Dow Chemical Company, Midland Michigan. Animals were acclimated to the laboratory environment for at least one-week prior to study start. Animals were identified via a code number transmitted by a subcutaneously implanted transponder.

Administration / exposure

Route of administration:
oral: gavage
Details on oral exposure:
Five male rats per dose level received 100, 200, or 300 mg of Bronopol per kg body weight as a 2%, 4%, or 6% mixture in distilled water by single dose gavage. Five female rats per dose level also received 100, 150, or 200 mg of the test material per kg body weight as a 2%, 3%, or 4% mixture in distilled water by single dose gavage. Rats were fasted the night prior to treatment. Feed was provided to all rats immediately following administration of the test material.
Males: 100, 200, 300 mg/kg bw
Females: 100, 150, 200 mg/kg bw
No. of animals per sex per dose:
Control animals:
Details on study design:
A Detailed Clinical Observation (DCO) was conducted for all rats prior to test material administration for comparison with the observations recorded throughout the study. Animals were observed a minimum of two times on the day of treatment. A DCO was done each day (including weekends and holidays) during the study. Hand-held and open-field observations included a careful physical examination according to an established format. For scored DCOs only observations other than typically expected were recorded. Observations were dictionary based, and the dictionary contained most of the common physical and neurologic abnormalities seen in toxicity studies. Since not all potential observations were contained in the dictionary, free-field descriptions also were allowed. Each animal was weighed, pre-study, the day of treatment, and on test days 2, 8, and 15. A necropsy was performed on all animals.

Animals submitted alive for necropsy were anesthetized by inhalation of carbon dioxide and were euthanized by decapitation after clamping of the trachea. A complete necropsy was conducted on all animals by a veterinary pathologist assisted by a team of trained individuals. The eyes were examined in situ using a moistened glass microscope slide applied to the corneal surface. Following inspection of the externum and body orifices, the nasal, cranial, oral, thoracic, and abdominal cavities were opened and the visceral organs were examined both in situ and following dissection, and tissues were not saved.
Means and standard deviations were calculated for body weights. The data were evaluated for statistical outliers by a sequential test (Grubbs, 1969); however, outliers were not routinely excluded from statistical analysis. An approximate LD50 was calculated by linear interpolation of the arc sine transformed data (Stephan, 1977).

Results and discussion

Effect levelsopen allclose all
Dose descriptor:
Effect level:
211 mg/kg bw
Based on:
test mat.
Dose descriptor:
Effect level:
193 mg/kg bw
Based on:
test mat.
Two male rats given 200 mg/kg and all males given 300 mg/kg died on test day 1 or 2. One female given 100 mg/kg and three females given 200 mg/kg died on test day 1.
Clinical signs:
Clinical observations in rats that died were consistent with their moribund condition. Three males and two females given 200 mg/kg, all females given 150 mg/kg, and all males and four females given 100 mg/kg survived the two-week observation period. Clinical observations for surviving rats given 100 or 200 mg/kg consisted of various combinations of: lacrimation, noisy respiration, decreased responsiveness to touch, decreased activity, decreased reactivity to handling, soft feces, vocalization, and soiling of the perioral, perinasal, perineal, and/or periocular regions. Clinical signs for surviving animals given 100 or 200 mg/kg diminished over time, and these animals were normal at study termination. Females given 150 mg/kg had no remarkable clinical observations.
Body weight:
Two of the surviving female rats given 200 mg/kg gained weight over the duration of the study. Two surviving male rats given 200 mg/kg lost weight between test days 1 and 2 or 8, but gained weight over the remainder of the study. All of the female rats given 150 mg/kg gained weight over the duration of the study. Three male rats and three female rats given 100 mg/kg gained weight over the duration of the study. One female rat and two male rats given 100 mg/kg lost weight between test days 1 and 2, but gained weight over the remainder of the study.
Gross pathology:
Male rats given 200 or 300 mg/kg and females given 100 or 200 mg/kg that died had treatment-related gross findings consisting of various combinations of: dark glandular mucosa of the stomach, dilatation of the stomach with cloudy fluid, perineal soiling, and hemolyzed blood in the gastrointestinal tract. Dark foci in the lungs were also noted in two males given 300 mg/kg that died. Surviving animals from all dose groups had no treatment-related gross pathologic observations.

Any other information on results incl. tables

Table 1. Mortality

[mg/kg bw]

Number of dead /
number of investigated

Time of death (range)


0/5 males
1/5 females

day 1


0/5 females



2/5 males
3/5 females

day 1
day 1


5/5 males

day 1 (4x), day 2 (1x)

Applicant's summary and conclusion

Interpretation of results:
Category 3 based on GHS criteria
Under the conditions of this study, the acute oral LD50 of Bronopol in Fischer 344 rats was approximately 211 mg/kg in males and approximately 193 mg/kg in females.