2-fluoro-6-trifluoromethylpyridine

Repeated dose toxicity: inhalation

Administrative data

Endpoint:

short-term repeated dose toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1999

Report date:

1999

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 412 (Subacute Inhalation Toxicity: 28-Day Study)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method B.8 (Subacute Inhalation Toxicity: 28-Day Study)

Deviations:

no

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

-

EC Number:

428-100-3

EC Name:

-

Cas Number:

94239-04-0

Molecular formula:

C6H3NF4

IUPAC Name:

2-fluoro-6-(trifluoromethyl)pyridine

Details on test material:

- Purity: 99.5%

Specific details on test material used for the study:

Substance ID: F6TF
Lot #: R646899
Purity: 99.5%

Test animals

Species:

rat

Strain:

other: Alpk:APfSD

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Age at study initiation: Approximately 6-7 weeks old on delivery
- Weight at study initiation: 250-275 g (males) and 167-217 g (females)
- Housing: 5 per cage, sexes separate, in multiple rat racks suitable for animals of this strain and the weight range expected during the course of
the study.
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22±3°C
- Humidity (%): 30-70%
- Air changes (per hr): At least 15 changes/hour
- Photoperiod (hrs dark / hrs light): 12 hours light, 12 hours dark

Administration / exposure

Route of administration:

inhalation: vapour

Type of inhalation exposure:

whole body

Vehicle:

clean air

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: The whole body exposure chambers consisted of a PERSPEX circular section subdivided into 10 equal segments by wire mesh partitions. The chamber was covered by an aluminium lid and stood on an aluminium base plate. The internal volume was approximately 100 litres.
- Source and rate of air: Nominal generation air flow rate 25 L/minute
- Method of conditioning air: clean, dry generation air
- System of generating particulates/aerosols: Each test atmosphere was generated by metering appropriate amounts of test compound onto the top of a jacketed condenser column heated to 40°C. A counter flow of clean, dry generation air passed the resultant vapour to the top of the exposure chambers (internal volume of approximately 100 litres) and dilution air was added as required in order to achieve a minimum of 12 air changes per hour. Air flows were monitored and recorded at approximately 30 minute intervals using variable area flowmeters and were altered as necessary to maintain the target concentrations.
- Temperature, humidity, pressure in air chamber: 18.2-24. 7°C; 27-72% humidity; pressure not reported
- Air change rate: minimum of 12 air changes per hour

TEST ATMOSPHERE
- Brief description of analytical method used: Samples were analysed using gas chromatography.
- Samples taken from breathing zone: yes

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The atmospheric concentration of the test substance was determined for each exposure concentration by analysis of the material sampled from a front facing port of the relevant exposure chamber using a Gastek 801 sampling pump and thermal desorption tube containing Carbotrap C (Supelco). Samples were analysed using gas chromatography.

Duration of treatment / exposure:

28 days

Frequency of treatment:

6 hours/day, 5 days/week

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

1.5 ppm

Doses / concentrations 2

Dose / conc.:

15 ppm

Doses / concentrations 3

Dose / conc.:

150 ppm

No. of animals per sex per dose:

5

Control animals:

yes, concurrent vehicle

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: daily

BODY WEIGHT: Yes
- Time schedule for examinations: The bodyweight of each rat was recorded on day 1, before the first exposure (on day 3) and thereafter once a week and prior to termination.

FOOD CONSUMPTION: Yes
- Food consumption: Food consumption was recorded continuously throughout the study for each cage of rats and calculated as a weekly mean (g food/rat/day) for each cage.

HAEMATOLOGY: Yes
- Time schedule for collection of blood: At termination
- Anaesthetic used for blood collection: Yes. All rats were killed by exsanguination under terminal anaesthesia induced by halothane Ph. Eur. vapour.
- How many animals: all surviving rats
- Parameters checked in table [No.1] were examined.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: At termination
- How many animals: all surviving rats
- Parameters checked in table [No.2] were examined.

URINALYSIS: Yes
- Time schedule for collection of urine: during week 4
- Metabolism cages used for collection of urine: Yes
- Animals fasted: Yes
- Parameters checked in table [No.2] were examined.

Sacrifice and pathology:

GROSS PATHOLOGY: Yes (see table No. 3)

HISTOPATHOLOGY: Yes (see table No. 3)

All animals were subjected to a full macroscopic examination. All submitted tissues from the control (0 ppm) and high (150 ppm) groups together with the liver, kidney, spleen, and abnormal tissue from the low (1.5 ppm) and intermediate (15 ppm) groups were routinely processed, embedded in paraffin wax, sectioned at 5 µm and stained with haematoxylin and eosin. Of the tissues processed, the top dose (150 ppm) and control (0 ppm) slides were examined by microscopy in the first instance, plus liver, kidney, spleen, and abnormal tissues from the mid (15 ppm) exposure concentrations.

Statistics:

Bodyweights were considered by analysis of covariance on pre-dosing (day 3) bodyweight, separately for males and females. No statistical analysis was performed for food consumption as there was only one observation per group. Haematology, blood and urine clinical chemistry were considered by analysis of variance. Male and female data were analysed together and the results examined to determine whether any differences between control and treated groups were consistent between the sexes. Organ weights were considered by analysis of variance and analysis of covariance on final bodyweight, separately for males and females. Summary data are presented for organ to bodyweight ratios but these were not analysed statistically as the analysis of covariance provides a better method of allowing for differences in terminal bodyweights. Analyses of variance and covariance were carried out using the MIXED procedure in SAS. Least-squares means for each group were calculated using the LSMEAN option in SAS PROC MIXED. Unbiased estimates of differences from control were provided by the difference between each treatment group least-squares mean and the control group least squares mean. Differences from control were tested statistically by comparing each treatment group least-squares mean with the control group least-squares mean using a two-sided Student's t-test, based on the error mean square in the analysis.

Results and discussion

Results of examinations

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

No clinical signs were noted during exposure throughout the study in controls and animals exposed to 1.46 ppm of the test substance. For animals exposed to 15.2 ppm, clinical signs including decreased activity, hunched posture and pilo-erection were noted during the first week of exposures and in general, the time to onset of these clinical signs increased throughout the week. Piloerection was noted in some animals on one day in the second week of exposures. No clinical signs were noted for these animals during the remainder of the study. For animals exposed to 159 ppm, clinical signs including hunched posture, decreased activity and pilo-erection were noted throughout the study. During the final week of exposures, salivation was also noted in animals exposed to this concentration.

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

A reduction in bodyweight compared with controls was seen in males exposed to 159 ppm from day 8 of the study, with a maximum reduction of 6% observed on day 15. After this date, group mean bodyweight showed convergence towards, but did not equal, control values by the end of the study. There were no effects on bodyweight in any other male group or in females.

Food consumption and compound intake (if feeding study):

no effects observed

Haematological findings:

effects observed, treatment-related

Description (incidence and severity):

Minor differences from control were confined to the group exposed to 159 ppm. Minimal decreases (which attained statistical significance) were seen for haemoglobin, red blood cell count and hematocrit values in animals exposed to 159 ppm, although for red blood cell count and hematocrit this only achieved statistical significance in females. Minimal increases (which attained statistical significance) were seen for platelet count, white blood cell count, lymphocyte count and large unstained cells in females exposed to 159 ppm. Prothrombin time was statistically significantly decreased in both sexes at this concentration. Although a relationship to treatment cannot be discounted, these changes were small and considered to be of no toxicological significance. Statistically significant decreases seen for white blood cell count, lymphocyte count, monocyte count and large unstained cells in males exposed to 1.46 ppm were due to two individual low values, and are considered to be unrelated to treatment. The small increase in activated partial prothrombin time in females exposed to 1.46 ppm showed no evidence of a dose response and is considered not to be treatment related.

Clinical biochemistry findings:

effects observed, treatment-related

Description (incidence and severity):

Differences from control were confined to the group exposed to 159 ppm and are considered to be related to treatment. In females, albumin (and consequently total protein) and gamma glutamyl transferase activities were statistically significantly increased. Cholesterol values were also statistically significantly increased in both sexes exposed to 159 ppm. Occasional minor and statistically significant deviations from control values were seen in intermediate exposure groups i.e. aspartate aminotransferase activity, calcium and sodium values, but these were not evident in the highest exposure group, showed no relationship to exposure, were seen in one sex only and are considered to be unrelated to treatment.

Urinalysis findings:

effects observed, treatment-related

Description (incidence and severity):

Differences from controls were confined to the group exposed to 159 ppm. A small but statistically significant reduction in pH was seen in both males and females exposed to 159 ppm. There was an apparent increase in urine volume in females at this exposure concentration, however, analysis of individual animal data showed this was due to a single high value and as such, this difference is considered to be unrelated to treatment. There was an increase in the presence of casts in urine of females exposed to 159 ppm. Below this concentration, there were no treatment related changes in females. In males, "few casts" were seen in the urine of treated animals, however, these were of insufficient magnitude to be of toxicological significance.

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

A statistically significant increase in liver weights adjusted for final bodyweight was noted in males and females exposed to 159 ppm (male liver weight increased by approximately 46%, females by 45%). Males exposed to 15.2 ppm showed a lesser but still statistically significant increase in liver weight (15% increase). A statistically significant increase in kidney weights adjusted for final bodyweight was observed in males exposed to 159 ppm. A small increase in absolute kidney weight was noted in males exposed to 15.2 ppm, however, this was not evident following adjustment for bodyweight and is considered to be unrelated to treatment. Testes weight (absolute and adjusted for final bodyweight) showed a small but statistically significant increase in males exposed to 159 and 15.2 ppm. Epididymides weight (absolute and adjusted for bodyweight) was statistically significantly increased in males exposed to 1.46 and 15.2 ppm (maximal increase of 15% in the group exposed to 15.2 ppm), however, as no change was evident at the highest exposure concentration, this is considered to be unrelated to treatment. Males exposed to 15.2 ppm showed an increase in adrenal weight adjusted for final bodyweight and females exposed to 1.46 ppm showed an increase in spleen weight adjusted final bodyweight. In the absence of any change in these organs at the higher exposure concentrations, this is considered to be of no toxicological significance. There were no effects on organ weight for any other organs examined.

Gross pathological findings:

no effects observed

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

Treatment-related changes were seen in the kidneys and liver. In the livers of males and female rats receiving 159 ppm there was minimal hepatocyte degeneration which was mainly centrilobular, comprising enlarged hepatocytes with disrupted or pale, ground glass cytoplasm and apoptosis. In the kidneys of females receiving 159 ppm there was minimal to slight vacuolar degeneration. All other histopathological findings are considered to be spontaneous and of no toxicological significance.

Effect levels

Key result

Dose descriptor:

NOAEC

Effect level:

15.2 ppm

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: changes in body weight, liver/kidney weight, and histopathological change at 159 ppm

Applicant's summary and conclusion

Conclusions:

28 day (Rat) NOAEC= 15.2 ppm

Executive summary:

Groups of 5 male and 5 female Alpk:APfSD (Wistar-derived) rats were exposed in circular whole body exposure chambers for 6 hours per day to 0 (control), 1.5, 15, or 150 ppm of the test substance for 5 days per week, for a period of 28 days. Clinical observations were daily throughout the study. Body weights were measured weekly and food consumption was measured continuously throughout the study. Urine samples were obtained during week 4 and at the end of the scheduled period, the animals were killed and subjected to a full examination post mortem. Cardiac blood samples were taken for clinical pathology from all animals, selected organs were weighed and specified tissues were taken for subsequent histopathology examination. 

 

Analysed concentrations were 0, 1.46 ± 0.24, 15.2 ± 0.82, and 159 ± 6.99 ppm for the 0, 1.5, 15, and 150 ppm concentrations. Exposure to the test substance at 159 ppm was associated with toxicity manifest as reduction in bodyweight (males only) and increased liver weight with associated histopathological change (minimal centrilobular hepatocyte degeneration). Kidney weight in males was increased and kidney histopathology (slight to minimal vacuolar degeneration) was seen in females, although the toxicological significance at this exposure concentration is unclear. Other effects observed at 159 ppm included clinical signs of decreased activity, hunched posture, piloerection and salivation, but as these signs principally appeared during exposure and were no longer present at post exposure examination, they are considered to be of little toxicological significance. Minimal changes in blood clinical chemistry (albumin, total protein, cholesterol, and gamma glutamyl transferase) and the presence of casts in the urine of females at this exposure concentration are considered to be treatment related. The increase in testes weight was small and not associated with any histopathological change and as such is considered to be of no toxicological significance. There were no toxicologically significant haematological changes at 159 ppm. There were no toxicologically significant changes at 1.46 and 15.2 ppm.

 

In this study, whole body exposure to 159 ppm of the test substance for 6 hours per day, 5 days per week for a period of 28 days produced clear signs of toxicity as shown by changes in body weight, liver/kidney weight, and histopathological change. Whole body exposure to 15.2 ppm produced no toxicologically significant effects. Whole body exposure to 1.4 ppm did not result in any treatment-related changes. The NOAEC was 15.2 ppm.