2,6-difluorobenzonitrile

Acute Toxicity: inhalation

Administrative data

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

25 February 1981 to 13 August 1981

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Study conducted in compliance with agreed protocols, using methodology 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:

1981

Report date:

1981

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 403 (Acute Inhalation Toxicity)

Deviations:

not applicable

Principles of method if other than guideline:

The acute inhalation toxicity of difluorobenzonitrile was assessed by exposing 3 groups of rats, for a period of 4 hours, to test atmospheres containing the vapour of the test material. The animals, and their exposure conditions, were closely monitored prior to and during exposure. The animals were observed over a 14 day period following exposure.

GLP compliance:

yes

Test type:

standard acute method

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

2,6-difluorobenzonitrile

EC Number:

217-589-7

EC Name:

2,6-difluorobenzonitrile

Cas Number:

1897-52-5

Molecular formula:

C7H3F2N

IUPAC Name:

2,6-difluorobenzonitrile

Details on test material:

- Physical state: pale brown crystalline solid
- Storage conditions: in a glass container in a fume cupboard at room temperature

Test animals

Species:

rat

Strain:

CD-1

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Age at study initiation: 6-8 weeks old
- Weight at study initiation: 149-203 g
- Housing: 5 per cage (by sex)
- Diet: Spratts Laboratory Diet ad libitum
- Water: Mains water ad libitum
- Source: Charles River UK, Margate, Kent

ENVIRONMENTAL CONDITIONS (holding room)
- Temperature (ºC): 22-23 ºC
- Humidity (%): 37% (mean)

ENVIRONMENTAL CONDITIONS (chamber)
- Temperature (ºC): 23-25 ºC

IN-LIFE DATES
- Group 1: 3 March 1981
- Group 2: 4 March 1981
- Group 3: 17 March 1981
- Group 4: 18 March 1981

Administration / exposure

Route of administration:

inhalation: vapour

Type of inhalation exposure:

whole body

Vehicle:

air

Remarks:

(the air supplies to the generator were dry, filtered and oil-free)

Details on inhalation exposure:

- Vapour generator: The generator that was used in the study was designed to produce and maintain an atmosphere containing the vapour of the test material at a concentration which could be varied by changing the flow rate of air through the generator vessel. During the study the generator was maintained at 50 ºC in a water bath. The vapour from the generator vessel passed through a column packed loosely with with glass wool and into the flask where it was diluted with air before entering the chamber. The glass wool packing prevented particulate material, formed as the vapour cooled, from reaching the chamber.

- Exposure chambers: The whole body exposure chambers used for the exposure were of square section and were fitted with pyramid tops, having an internal volume of approx. 0.13 m³. Each chamber was divided by wire mesh to provide 10 separate animal compartments. The test atmosphere entered through a port at the base centre of the chamber and passed out through small holes in the lower edge of the square section. Each chamber was positioned inside a large glass cabinet equipped with an extractor fan exhausting to atmosphere through a collection filter.

- Generation of the test atmospheres: The test material was heated in a container in a water bath help at 50 ºC. Once melted, 100 g of the test material was transferred to the vapour generator. To achieve the different exposure concentrations the dilution air was adjusted to a flow rate of between 5.0 and 23.8 L/min. To start the exposure a measured flow of air between 1.2 and 20.0 L/min was passed through the generator vessel. Total air flow to the chamber was 25 L/min.

Analytical verification of test atmosphere concentrations:

yes

Duration of exposure:

4 h

Concentrations:

control, 0.19 g/m³, 0.83 g/m³, 2.64 g/m³

No. of animals per sex per dose:

5

Control animals:

yes

Details on study design:

-Exposure: Five male and five female rats were placed into separate compartments of the exposure chamber and the flow rate adjusted to achieve the required atmospheric concentration of test material. Following 4 hours exposure the supply of air to the generator vessel was discontinued and the exposure chamber was allowed to clear for 60 minutes before the rats were removed for examination. This procedure was followed for each test group. The control group was treated similarly but received clean air only for 4 hours (air flow rate to the control group was 25 L/min). Following exposure the rats were kept in a ventilated cabinet for 18 hours and then returned to the holding room for the remainder of the 14 day observation period.

- Chamber atmosphere analysis: Five air samples were taken from the chamber during each exposure and analysed to determine the concentration of the test material in the chamber atmosphere. The chamber temperature was measured with a mercury bulb thermometer and recorded at 30 minute intervals during the exposure.

- Observations: The rats were observed continuously during the exposure period, for signs of reaction to the test material, and at least twice daily during the observation period. All animals were weighed daily from the day following delivery to the end of the exposure period and the amount of food and water consumed by each cage of rats was measured daily from the day following arrival.

- Terminal studies: Following the 14 day observation period the animals were injected with sodium pentobarbitone and exsanguinated. The animals were then subject to detailed macroscopic and microscopic examination. The lungs were removed and weighed in order to calculate the lung weight to body weight ratio and were later preserved and embedded in wax so that cross sections could be taken for further analysis.

Results and discussion

Effect levels

Effect levels 1

Sex:

male/female

Dose descriptor:

LC50

Effect level:

> 2.64 other: g/m3

Based on:

test mat.

Exp. duration:

4 h

Effect levels 2

Sex:

male/female

Dose descriptor:

other: NOEL

Effect level:

0.19 other: g/m3

Based on:

test mat.

Exp. duration:

4 h

Mortality:

There were no deaths during the study.

Clinical signs:

other: - During the exposure: Abnormal body posture, closing or partial closing of the eyes, peripheral vasodilation, ataxia and dyspnoea were observed in a proportion of rats exposed to the test material at a concentration of 2.64 g/m³ and 0.83 g/m³. Additional

Body weight:

There was a moderate decrease in group mean body weight for 1-2 days following exposure to the test material at 2.64 g/m³ and subsequently the rate of body weight gain was similar to that of the controls. The rates of body weight gain for animals dosed at the lower concentrations were not significantly affected by exposure. The difference between the rate of body weight gain for male rats from these groups and the controls was evident before exposure and was considered to be of no toxicological significance.

Gross pathology:

The small red or grey areas in the lungs of the majority of the animals dosed at the two lower test concentrations were considered to be indicative of a minimal chronic disease condition and of no toxicological importance. There were no variations from normal which could be attributed to exposure to the test material.

Other findings:

MICROSCOPIC PATHOLOGY
- Treatment-related changes: No histological changes were seen that were considered to be of any toxicological significance.

- Incidental changes: All the changes observed in lungs of control and treated rats were inflammatory in nature and characterised by both acute and chronic inflammatory cells. The incidence of lung changes was considered greater in rats in the 0.83 g/m³ dosage group compared with the control and other dosage groups. In the absence of any obvious dose relationship these changes were considered unlikely to be related to the single exposure to the test compound. Other changes seen and not considered to be toxicologically significant included occasional parenchymal foci of mononuclear cells in the liver and renal corticomedullary foci of mineralisation in a number of animals from all groups.

Applicant's summary and conclusion

Interpretation of results:

not classified

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

Under the conditions of the test, the maximum achievable concentration of the test material did not elicit mortality when groups of rats were exposed, by whole-body exposure, over a period of 4 hours. The study is considered to be reliable, relevant and adequate for risk assessment and classification and labelling purposes.

Executive summary:

The acute inhalation toxicity of the test material was assessed by exposing 3 groups of 5 male and 5 female rats, for a period of 4 hours, to test atmospheres containing the vapour of the test material. Exposure concentrations of 0.19, 0.83 and 2.64 g/m³ were investigated and compared to a control group who were exposed to air only. During the exposure period the animals were continuously observed for any sign of reaction to the test material. Following exposure, the animals were observed at least twice daily during the 14 day observation period. At the end of the observation period the animals were killed and subjected to microscopic and macroscopic examination. During the study none of the animals died. Both the macroscopic results and the microscopic results showed no variations from normal which could be attributed to exposure of the animal to the test material. No changes were seen that were considered to be of any toxicological significance. The acute inhalation median lethal concentration of the test material was estimated to be in excess of 2.64 mg/m³ to both male and female rats.