2-methylglutaronitrile

Repeated dose toxicity: inhalation

Administrative data

Endpoint:

short-term repeated dose toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2001/02/20-2001/10/17

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Guideline study with some deviations (Males only were tested, Food consumption was not measured).

Data source

Reference

Reference 1

Reference Type:

study report

Title:

Unnamed

Year:

2001

Report date:

2001

Reference 2

Reference Type:

publication

Title:

Unnamed

Year:

2003

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

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

Deviations:

yes

Remarks:

: 1- Males only were used in this study, 2- Food consumption was not measured in this study.

Principles of method if other than guideline:

Not aplicable.

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

2-methylglutaronitrile

EC Number:

224-923-5

EC Name:

2-methylglutaronitrile

Cas Number:

4553-62-2

Molecular formula:

C6H8N2

IUPAC Name:

2-methylpentanedinitrile

Details on test material:

- Name of test material (as cited in study report): H24687
- Molecular formula (if other than submission substance): no data
- Molecular weight (if other than submission substance): no data
- Smiles notation (if other than submission substance): no data
- InChl (if other than submission substance): no data
- Substance type: no data
- Physical state: a colorless liquid
- Purity test date: no data
- Expiration date of the lot/batch: no data
- Stability under test conditions: stable under the conditions of the study
- Storage condition of test material: no data
- Other:

Test animals

Species:

rat

Strain:

other: Crl:CD(SD)IGS BR

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories, Inc.
- Age at study initiation: 9 weeks old
- Weight at study initiation: between 268 and 333 g
- Fasting period before study: yes
- Housing: Individually in suspended, stainless steel, wire-mesh cages.
- Diet (e.g. ad libitum): ad libitum except during exposure
- Water (e.g. ad libitum): ad libitum except during exposure
- Acclimation period: yes. Prior to the start of the study, all rats were placed in restrainers for 15-minute period on 2 different days to acclimate the rats to the restrainers.


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 +/- 3 °C
- Humidity (%): 50 +/- 20 %
- Air changes (per hr): no data
- Photoperiod (hrs dark / hrs light): 12 hrs dark/12 hrs light


IN-LIFE DATES: no data

Administration / exposure

Route of administration:

inhalation

Type of inhalation exposure:

nose only

Vehicle:

other: unchanged (no vehicle)

Remarks on MMAD:

MMAD / GSD: The 5 and 25 mg/m3 concentrations measurements were almost 100 % vapor while the 200 mg/m3 was mostly aerosol (160 mg/m3) with the remainder (40 mg/m3) being vapor. The aerodynamic particle size of the aerosol in the 200 mg/m3 chamber was found to have a mass median aerodynamic diameter of 3.8 µm ± 0.1 (mean of 4 measurements). The aerosol size was not measured in the other chambers because of the insignificant amount of aerosol present (less than 1%).
See details in Table 7.5.3/1

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: no data
- Method of holding animals in test chamber: the rats were individually restrained in perforated stainless steel cylinders with conical nose pieces.
- Source and rate of air: filtered, low-pressure air (30 L/min)
- Method of conditioning air: no data
- System of generating particulates/aerosols: At concentration of 5 and 25 mg/m3, test atmospheress were generated by metering liquid substance into a heated, Instatherm Flask at 150°C. Nitrogen (2 L/min) was used to carry the H24687 vapor from the flask into a glass transfer tube where it was mixed with filtered, low pressure air and fed into the top of the exposure chamber. At the concentration of 200 mg/m3, an aerosol/vapor mixture was produced by spraying liquid H-24687 using an air-driven nebulizer into the inlet of the exposure chamber with an airflow.
- Temperature, humidity, pressure in air chamber: 22 °C, 38 to 42%, no data on the pressure chamber
- Air flow rate: 30 L/min
- Air change rate: 12 air changes per hour
- Method of particle size determination: no data
- Treatment of exhaust air: test atmospheres were exhausted trough a glass cold trap followed by an MSA charcoal/HEPA filter cartridge prior to disharge into the fume hood.


TEST ATMOSPHERE
- Brief description of analytical method used: aliquots of impinger solutions were injected onto a HP-17 column in a Hewlett Packard model 5890 series gas chromatograph equipped with a flame ionization detector. Use of standard samples (dilution of H-24687 in acetone).
- Samples taken from breathing zone: yes


VEHICLE (if applicable): none

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Samples of the H-24687 vapor component were taken at approximately 1-hour intervals during the study in all chambers. The atmospheric aerosol concentration of the substance was determined by gravimetric filter analysis. Filter samples were taken 4 times during the study for the 5mg/m3 chamber and once daily for the 25 mg/m3 chamber. For the 200 mg/m3 chamber, aerosol samples were taken simultaneously with the GC samples approximately 1-hour intervals. During 200 mg/m3 chamber sampling, known volumes of chamber atmosphere were drawn from the breathing zone of the rats trough a sampling train consisting of a pre-weighed Gelman (Type A/E) glass fiber filter followed by a midget glass impinger containing acetone as the collection medium. For GC analysis of the 5 and 25 mg/m3 chambers, the same type of sampling train was used, however, the filters were not used for analysis. The atmosphere concentration of aerosol was determined from the pre-and post-sampling filter weights. To determine the atmospheric vapor concentration, aliquots of impinger solutions were injected onto a HP-17 column in a Hewlett Packard model 5890 series gas chromatograph equipped with a flame ionization detector. Use of standard samples (dilution of H-24687 in acetone).

Duration of treatment / exposure:

4 weeks

Frequency of treatment:

6 hours/day, 5 days/week (20 exposures)

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
0, 5, 25, 200 mg/m3
Basis:
nominal conc.

Doses / concentrations 2

Remarks:

Doses / Concentrations:
0, 5.1, 24 and 200 mg/m3
Basis:
other: actual mean concentrations

No. of animals per sex per dose:

20 males per dose (10 for the main study and 10 for the satellite group)

Control animals:

yes

Details on study design:

- Dose selection rationale: Prior to the study, range-finding experiments were conducted in groups of male and female rats to determine the appropriate concentration for the study of subchronic toxicity of the substance. First, the acute toxicity was determined by exposing male and femalerats for 4 hours to a concentration of 1850 mg/m3 of test substance. 2 of 5 male rats died within 1 day of the exposure, but none of female rats died.Therefore, male rats were used in this study, because of the apparently more sensitiveness. Following the acute study, a repeated dose was conductedin male rats for 6 hours/day for 4 days at 10, 46 and 220 mg/m3. Slight, transient body weight losses occurred during the exposure period and no clinical signs of toxicity were observed. In a final range-finding study, male rats were exposed to the substance for 5 or 6 hours/day for 3 days at a mean concentration of 5.3 mg/m3. A minimal weight loss was observed in 3 of 5 male rats on the day after the first exposure but no other weight effects were observed and no clinical signs of toxicity were observed. Based on the above information, design concentration of 5, 25 and 200 mg/m3 were selected.

- Rationale for animal assignment (if not random): random

- Rationale for selecting satellite groups: A recovery period of approximately 4 weeks was included to determine recovery from any potential effects.

- Post-exposure recovery period in satellite groups: 28 days

Positive control:

No data

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: no data
- Cage side observations checked in table 7.5.3/2 were included.


DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: during each exposure. Throughout the recovery period, the clinical signs were observed weekly.


BODY WEIGHT: Yes
- Time schedule for examinations: at least twice a week during the exposure phase (daily on the first 5 exposure days). Throughout the recovery period, surviving animals were weighed weekly.


FOOD CONSUMPTION:
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: No data


FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight
gain data: No data


WATER CONSUMPTION: No data



OPHTHALMOSCOPIC EXAMINATION: No data



HAEMATOLOGY: Yes
- Time schedule for collection of blood: At the end of the 4-week exposure period and at the end of the 4-week recovery period
- Anaesthetic used for blood collection: Yes (light carbon dioxide anesthesia)
- Animals fasted: Yes, for 16 hours
- How many animals: 10 male rats per group at the end of the 4-week exposure period and remaining rats at the end of the 4-week recovery period
- Parameters checked in table 7.5.3/3 were examined.


CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: At the end of the 4-week exposure period and at the end of the 4-week recovery period
- Animals fasted: Yes, for 16 hours
- How many animals: 10 male rats per group at the end of the 4-week exposure period and remaining rats at the end of the 4-week recovery period
- Parameters checked in table 7.5.3/4 were examined.


URINALYSIS: Yes
- Time schedule for collection of urine: At the end of the 4-week exposure period and at the end of the 4-week recovery period
- Metabolism cages used for collection of urine: No data
- Animals fasted: Yes, for 16 hours
- Parameters checked in table 7.5.3/3 were examined.


NEUROBEHAVIOURAL EXAMINATION: Yes
- Time schedule for examinations: prior to dosing, 4 weeks after initiation of dosing, and after 4 weeks of recovery.
- Dose groups that were examined: 10 male rats for each groups of animal (10/20 animals)
- Battery of functions tested: FOB (Functional Observational Battery) and Motor Activity (MA)

Sacrifice and pathology:

GROSS PATHOLOGY: Yes (see Table 7.5.3/4)
HISTOPATHOLOGY: Yes (see Table 7.5.3/4)

Other examinations:

Neurobehavioral Evaluations:
1- Functional Observational Battery (FOB): yes. Ten rats/group were evaluated prior to dosing to establish their baseline FOB parameters. The FOB was conducted again on the same rats approximately 4 weeks after inititation of dosing, and after approximately 4 weeks recovery.
2- Motor activity (MA): yes, conducted immediately following FOB assessments. Rats were individually tested in 1 of 30 nominally identical, automated activity monitors (Coulboum Instruments).

Statistics:

Yes, except for Bartlett’s test (p < 0.005), significance was judged at p < 0.05. Separate analyses were performed on the data for each gender.
See table 7.5.3/5 for details on method used.

Results and discussion

Results of examinations

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

not examined

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

not examined

Haematological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

no effects observed

Behaviour (functional findings):

no effects observed

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

no effects observed

Histopathological findings: non-neoplastic:

no effects observed

Histopathological findings: neoplastic:

not examined

Details on results:

CLINICAL SIGNS AND MORTALITY: Clinical signs of toxicity were absent in rats exposed to test material in this study. Sporadic cases of alopecia were observed in some rats, especially in the 25 mg/m3. In addition, ocular discharges were observed in many rats after the daily exposure. These findings were observed in control rats also and are frequently seen in inhalation studies where animals are exposed in restrainers.
All animals survived to study termination.

BODY WEIGHT AND WEIGHT GAIN: During the period including the Day 0 to the Day 12, the difference between the group of animals exposed to the highest concentration (200 mg/m3) and the control group was not significant. From Day 15 to Day 26, the body-weight gain rate in the 200 mg/m3 group was depressed compared to that of the control group. As there is no information about the food consumption, it is impossible to conclude about the origin of the difference of body weight gain observed. The affected group resumed a normal weight-gain rate during the 4-week recovery period. The other test groups did not appear to be significantly affected by test material exposure. See details in Table 7.5.3/6 and 7.5.3/7.
HAEMATOLOGY: There were no toxicologically significant changes in hematology or coagulation parameters in male rats exposed to 5, 25 or 200 mg/m3. Male rats exposed to 200 mg/m3 for 4 weeks had minimally decreased red cell mass and accelerated red cell production. These changes were indicated by minimally decreased RBC, HGB, and HCT, and appropriately increased reticulocytes and MCV. Only increased reticulocytes were statistically significant. Because the magnitude of change in RBC parameters was so small (97-99% control group means), the red cell changes were not considered adverse.
After a 1-month recovery period, RBC mass parameters in 200 mg/m3 males were similar to or greater than control values. Reticulocytes were minimally decreased (statistically significant); decreased reticulocytes are not relevant in the face or normal RBC mass.
At the end of treatment, there were no statistically significant alterations in coagulation parameters; therefore, coagulation parameters were not measured at the end of the recovery period.

CLINICAL CHEMISTRY: There were no toxicologically significant changes in clinical chemistry parameters in rats exposed to 5, 25, or 200 mg/m3. All statistically significant changes were considered non-adverse (not toxicologically significant).
Creatinine was minimally increased in male rats exposed to 200 mg/m3. Increased creatinine can be an indicator of decreased glomerular filtration rate. However, in this study, other indicators of glomerular filtration were not affected (urea nitrogen, inorganic phosphorus). In individual animals, there was no correlation between urine concentration (as measured by osmolality) and serum creatinine. This suggests that increased creatinine was not related to either dehydration or renal insufficiency. In addiation, there were no organ weight or histologic alterations in renal parameters. After 4 weeks of recovery, creatinine concentrations in rats previously exposed to 200 mg/m3 were similar to control group values. Therefore, the minimally increased creatinine was considered non-adverse.

URINALYSIS: There were no statistically or toxicologically significant changes in parameters in rats exposed to 5, 25, or 200 mg/m3.

NEUROBEHAVIOUR: For all FOB parameters and Forelimb and Hindlimb Grip Strength, Hindlimb Foot splay there were no test substance-related changes in males exposed to any concentration of 2-methylglutaronitrile.
Concerning the motor activity, there were no test substance-related effects on duration of movement or number of movements for males exposed to any concentration of 2-methylglutaronitrile. Males assigned to the 25 or 200 mg/m3 groups had significantly high mean duration of movements during the first 10-minute interval for the baseline evaluation. However, test substance administration had not been initiated, and therefore, this statistical difference was not considered to be test substance related.

ORGAN WEIGHTS: There were no test substance-related organ weight effects. In test day 28 rats, increased heart weight relative to body weight in 5, 25, and 200 mg/m3 males was not associated with changes in other heart parameters and was consistent with effects occurring secondary to decrements in body weight. Therefore, these organ weight changes were not considered to be test substance-related.

GROSS PATHOLOGY: Gross observations noted were sporadic across groups and were not test substance related.

HISTOPATHOLOGY: NON-NEOPLASTIC: There were no test substance-related microscopic lesions observed. One 200 mg/m3 male rat had minimally pigment in the spleen. The amount of splenic pigment in other 200 mg/m3 animals was considered to be within the range of that seen in spleens of control rats of this strain and age.
All other microscopic observations noted are known to occur spontaneaously in rats of this strains and age and were not present in a dose-responsefashion in either incidence or severity.

Effect levels

1

Dose descriptor:

NOAEC

Effect level:

200 mg/m³ air (nominal)

Based on:

test mat.

Sex:

male

Basis for effect level:

other: see 'Remark'

2

Dose descriptor:

NOEC

Effect level:

25 mg/m³ air (nominal)

Sex:

male

Basis for effect level:

other: For the same effects than above.

Target system / organ toxicity

Critical effects observed:

not specified

Any other information on results incl. tables

Table 7.5.3/6: Average body during 28 days of treatment and after the recovery period. All animals were weighted (20 measures between Day 0 and Day 28, 10 measures between Day 28 and Day 56)

Analytical concentration (mg/m^3)	Body Weights (g)
	Day 0	Day 12	Day 15	Day 26	Day 28^a	Day 56
0	301.1±14.1	348.8±17.6	358.2±20.5	398.6±25.1	381.0±35.4	478.7±36.8
5.1	302.0±14.7	345.0±26.4	352.2±29.2	392.6±48.2	378.5±55.0	502.2±50.2
24	301.0±14.8	341.8±20.0	349.5±22.9	384.9±30.8	371.9±38.4	469.0±40.5
200	299.9±16.1	333.9±22.5	340.2*±25.0	376.8*±27.5	361.0±37.2	469.4±31.0

* Statistically significant difference from control at p<0.05 by trend test (Jonckheere-Terpstra)

^a Weight losses due to fasting period of rats prior to clinical pathology evaluations

Table 7.5.3/7:Average body weight gains during 28 days of treatment and after the recovery period.All animals were weighted (20 measures between Day 0 and Day 28, 10 measures between Day 28 and Day 56)

Analytical concentration (mg/m^3)	Exposure (Day)
	0-1	6-9	9-12	22-26	28-35
0	3.2±5.2	7.2±5.8	17.6±5.0	19.6±7.6	29.1±13.9
5.1	1.9±4.6	8.5±5.1	14.4±6.3	17.9±17.1	27.2±8.6
24	0.2±5.5	7.1±5.0	13.8*±5.2	18.4±3.6	32.8±9.8
200	1.2±3.1	3.1*±5.2	12.7*±5.6	16.9±5.8	34.1±12.9

* Statistically significant difference from control at p<0.05 by trend test (Jonckheere-Terpstra)

Applicant's summary and conclusion

Conclusions:

Under the conditions of this study, the no-observed-adverse-effect level (NOAEC) is greater than 200 mg/m3 (based on the decrease on the Body weight gain at 200 mg/m3 compared to control groups). The Food consumption was not examined. Therefore, this effect was likely to be related to treatement (worst case), the body weight gain was normal again and similar to the control group during the recovery period. Therefore, body weight gain reduction was not considered as an adverse effect. The no-observed-effect level NOEC is 25 mg/m3 (based on body weight gain reduction and on haematologic parameters ).

Executive summary:

In a subacute inhalation toxicity study performed according to OECD 412 guideline and in compliance with GLP, 2-Methylglutaronitrile (H-34687) (purity: 99.6%) was administered to 20 male Crl:CD (SD) IGS BR rats/concentration by nose only exposure at concentrations of 0, 5, 25, and 200 mg/m³(0, 0.005, 0.025 and 0.2 mg/L) for 6 hours per day, 5 days/week for a total of 20 days. The animals were exposed to vapors of 2-Methylglutaronitrile produced by evaporating liquid H-24687 heated under nitrogen. At the highest concentration (200 mg/m³), an aerosol/vapor mixture was produced by spraying liquid H-24687 using a nebulizer and high-pressure air. Only a small amount of aerosol (less than 0.2 mg/m³) was present at the 2 lowest concentrations.

 

At the end of the exposure period, blood and urine samples were collected from 10 rats/group and these rats were sacrificed for pathologic examination. A subgroup of 10 rats/group was given neurobehavioral tests. After a 4-week recovery period, these same rats were again given clinical and neurobehavioral evaluations, and sacrificed for pathologic evaluations.

Clinical signs and body weight were observed throughout the exposure period and during the recovery period. The hematology and clinical chemistry analyses, the urinalysis, organ weights, gross pathology and histopathology analyses were performed at the sacrifice of the animal.

 

No effect was observed for all parameters examined except a slight /transient effect on body weight gain and a statistically significant increased of reticulocytes. Indeed, at the highest concentration tested (200 mg/m³), the body weight gain was significantly lower in this group of rats (for a period between Day 15 and Day 26) than in the control group. The body weight gain was normal again and similar to the control group during the recovery period. As there is no information on the food consumption, no relevant link can be established between this depressed body weight gain and the Substance tested. Furthermore, this depressed body weight gain can not be considered as an adverse effect, because the rats exposed to the highest concentration did not present a true loss of weight. They continued to gain weight but in a lower extent in comparison to the control group. Furthermore, reticulocyte increase was not relevant in the face of normal RBC mass and thus the changes in reticulocyte values were not considered to be adverse.

 

Under the test conditions, the NOAEC is greater than 200 mg/m³ (0.2 mg/L), based on the decrease on the Body weight gain at 200 mg/m³compared to control groups and on a increased of reticulocytes. The NOEC is 25 mg/m³ (0.025 mg/L) for the same effects.

The 2-Methylglutaronitrile is therefore not classified as specific target organ toxicity for repeated exposure by inhalation according to the CLP Regulation (1272/2008).

 

This study in the rat is acceptable as it satisfies the guideline requirement (OECD 412) for a subacute inhalation study in rats (Kr.2).