Pentane-2,4-dione

Repeated dose toxicity: inhalation

Administrative data

Endpoint:

repeated dose toxicity: inhalation

Remarks:

other: 9 days

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Conduction and documentation of study acceptable. Literature reference and study report available.

Data source

Reference

Reference 1

Reference Type:

study report

Title:

Unnamed

Year:

1984

Report date:

1984

Reference 2

Reference Type:

publication

Title:

Unnamed

Year:

1986

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

other: stated in report

Deviations:

no

Principles of method if other than guideline:

Four groups, each consisting of 10 male and 10 female Fischer F-344 rats (COBS CDF F-344/CrlBR; age at study start 51 days) were exposed (whole body) 6 hours per day/5 days per week, for 9 days to 2,4 - pentanedione-vapours (9 days expos ure period interrupted by a two days non-exposure period after exposure day 5); 2,4-pentanedione concentration in the exposure chamber (nominal concentrations 0, 200, 400 and 800 ppm corresponding to actual mean concentrations of 0, 197, 418 and 805 ppm, respectively) measured every 33 min during the exposure; clinical (every day prior, during and after exposure) and hematological (at sacrifice) parameters determined; body weights and organ weights (liver, heart, brain, lungs, thymus, kidneys, testes) were measured; necropsy on each rat; histopathology on high dose and control animals only; in addition histopatholgic examination of nasal turbinates in all dose groups.

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Pentane-2,4-dione

EC Number:

204-634-0

EC Name:

Pentane-2,4-dione

Cas Number:

123-54-6

Molecular formula:

C5H8O2

IUPAC Name:

pentane-2,4-dione

Details on test material:

- Name of test material (as cited in study report): 2,4-Pentanedione
- Physical state: liquid
- Stability under test conditions: stable

Test animals

Species:

rat

Strain:

Fischer 344

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratories, Kingston, NY, USA
- Age at study initiation: 36 - 38 days
- Weight at study initiation:
- Fasting period before study: not reported
- Housing: individulally or two/cage
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: 5 days


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 69 to 74 °F (usually 70 to 71 °F)
- Humidity (%): 13 to 63 (usually 35 to 45%)
- Air changes (per hr): approx. 14
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:

inhalation

Type of inhalation exposure:

whole body

Vehicle:

other: unchanged (no vehicle)

Remarks on MMAD:

MMAD / GSD: not reported

Details on inhalation exposure:

Liquid 2,4-pentanedione was metered from a piston pump into a heated-glass evaporator. The temperature in the evaporator was maintained at the lowest-revel sufficient to vaporize the liquid. The resultant vapor was carried into the chamber by a countercurrent air stream that entered the bottom of the evaporator.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Gas chromatographic analysis of concentrations at least once per hour. Concentrations were 805 (+/- 15.2) ppm, 418 (+/- 4.2) ppm, 197 (+/- 2.1) ppm, No test substance in control chamber

Duration of treatment / exposure:

5d + 4d with a 2d non-exposure period in between (total 9d exposure)

Frequency of treatment:

6 hrs/day, 5 days/week

Doses / concentrations

Remarks:

Doses / Concentrations:
0, 197, 418, 805 ppm
Basis:
analytical conc.

No. of animals per sex per dose:

10

Control animals:

yes, concurrent vehicle

Details on study design:

Post-exposure period: 1 d
- Dose selection rationale: preliminary acute reports
- Rationale for animal assignment (if not random): random
- Post-exposure recovery period in satellite groups: no

Positive control:

not applicable

Examinations

Observations and examinations performed and frequency:

Cage side observations: Yes, daily

DETAILED CLINICAL OBSERVATIONS: Yes


BODY WEIGHT: Yes


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


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


WATER CONSUMPTION: No


OPHTHALMOSCOPIC EXAMINATION: No


HAEMATOLOGY: Yes
- Time schedule for collection of blood: after sacrifice
- Anaesthetic used for blood collection: Yes methoxyflurane
- Animals fasted: No data
- How many animals: all
- Parameters checked in table [appendix 3] were examined.


CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: after sacrifice
- Animals fasted: No data
- How many animals: all
- Parameters checked in table [appendix 3] were examined.


URINALYSIS: no


NEUROBEHAVIOURAL EXAMINATION: No

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes

Other examinations:

none

Statistics:

Results of quantitative continuous variables (such as body weight changes) were inter-compared among the concentration groups and one control group by use of analysis of variance (ANOVA). Bartlett's homogeneity of variance and Duncan's multiple range tests. The latter was used to delineate which exposure groups differed from the control, when F from the analysis of variance was significant. If Bartlett's test indicated hetero-geneous variances, all groups were compared by an ANOVA for unequal variances followed if necessary by t-tests. Corrected Bonferroni probabilities were used for t-test comparisons. The fiducial limit of 0.05 (two-tailed) was used as the critical level of significance for all comparisons.

Results and discussion

Results of examinations

Clinical signs:

effects observed, treatment-related

Mortality:

mortality observed, treatment-related

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

not specified

Food efficiency:

not specified

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

not specified

Ophthalmological findings:

not examined

Haematological findings:

effects observed, treatment-related

Clinical biochemistry findings:

not specified

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Gross pathological findings:

no effects observed

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

no effects observed

Details on results:

Mortality: No animal died.
Clinical observation: Clinical signs of irritancy (partial eyelid closure, periocular and pe-rioral wetness) were observed in few females of the 800 ppm exposure group; no expo-sure-related clinical signs in other groups.
Body weights: Transient body weight loss were observed during the first week of expo-sure in males and females of the 800 ppm group; significantly reduced body weight gain in both sexes at 800 ppm and in male rats at 400 ppm throughout the study; no body weight alterations in the 200 ppm dose groups.
Organ weights: Due to the body weight loss in 800 ppm exposure group absolute organ weights of brain, liver, kidney and lung/bronchi were lowered. The relative weights of these organs were within or higher than control values. Absolute and relative thymus weight in males and females of 800 ppm dose group were decreased (minus 15 %, sta-tistically significant). Also the relative thymus weight in males of 400 ppm dose group was decreased, but not statistically significant (minus 11 %). No differences in organ weights in 200 ppm dose group.
Hematology: At 800 ppm significant leucocytosis in both sexes; statistically significant increase in lymphocyte count in male rats of high dose group; significant increased mean corpuscular hemoglobin concentration and mean corpuscular hemoglobin in male rats were within the range of historical control values. By the study authors these altera-tions were not considered toxicologically significant because there was no effect in red blood cell count or in hemoglobin concentration. No changes in hematologic parameters were observable in animals of mid and low dose groups.
Histopathology: No treatment-related gross lesions; exposure-related inflammation of nasal mucosa, seen as multifocal areas of congestion, epithelial vacuolization, and lym-phocyte or neutophile infiltration of the submucosa, in all exposed rats; necrosis of the nasal mucosa frequently in 800 ppm rats, occasionally at 400 ppm and absent at 200 ppm; mild laryngitis in 2 males rats of the 800 ppm -group. No lesions observable in the lower respiratory tract (trachea and lung).
The biological significance of the mild vacuolization of the brain stem in two males of the 800 ppm group discussed by the study authors is not known.

Effect levels

1

Dose descriptor:

NOEC

Effect level:

197 ppm

Sex:

male/female

Basis for effect level:

other: overall effects

2

Dose descriptor:

LOAEC

Effect level:

805 ppm

Sex:

male/female

Basis for effect level:

other: body weight; haematology; organ weights; histopathology

Target system / organ toxicity

Critical effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

The NOEL of the nine days whole body vapour inhalation tests on rats was considered to be 200 ppm.

Executive summary:

2,4 -Pentanedione was assesses in a nine day whole body vapour inhalation assay on rats. Four groups, each consisting of 10 male and 10 female Fischer F-344 rats (COBS CDF F-344/CrlBR; age at study start 51 days) were exposed (whole body) 6 hours per day/5 days per week, for 9 days to 2,4 - pentanedione-vapours (9 days expos ure period interrupted by a two days non-exposure period after exposure day 5); 2,4-pentanedione concentration in the exposure chamber (nominal concentrations 0, 200, 400 and 800 ppm corresponding to actual mean concentrations of 0, 197, 418 and 805 ppm, respectively) measured every 33 min during the exposure; clinical (every day prior, during and after exposure) and hematological (at sacrifice) parameters determined; body weights and organ weights (liver, heart, brain, lungs, thymus, kidneys, testes) were measured; necropsy on each rat; histopathology on high dose and control animals only; in addition histopatholgic examination of nasal turbinates in all dose groups.

No animal died.Clinical signs of irritancy (partial eyelid closure, periocular and perioral wetness) were observed in few females of the 800 ppm exposure group; no exposure-related clinical signs in other groups. Transient body weight loss were observed during the first week of exposure in males and females of the 800 ppm group; significantly reduced body weight gain in both sexes at 800 ppm and in male rats at 400 ppm throughout the study; no body weight alterations in the 200 ppm dose groups. Due to the body weight loss in 800 ppm exposure group absolute organ weights of brain, liver, kidney and lung/bronchi were lowered. The relative weights of these organs were within or higher than control values. Absolute and relative thymus weight in males and females of 800 ppm dose group were decreased (minus 15 %, statistically significant). Also the relative thymus weight in males of 400 ppm dose group was decreased, but not statistically significant (minus 11 %). No differences in organ weights in 200 ppm dose group. At 800 ppm significant leucocytosis in both sexes; statistically significant increase in lymphocyte count in male rats of high dose group; significant increased mean corpuscular hemoglobin concentration and mean corpuscular hemoglobin in male rats were within the range of historical control values. By the study authors these alterations were not considered toxicologically significant because there was no effect in red blood cell count or in hemoglobin concentration. No changes in hematologic parameters were observable in animals of mid and low dose groups. No treatment-related gross lesions, exposure-related inflammation of nasal mucosa, seen as multifocal areas of congestion, epithelial vacuolization, and lymphocyte or neutophile infiltration of the submucosa, in all exposed rats; necrosis of the nasal mucosa frequently in 800 ppm rats, occasionally at 400 ppm and absent at 200 ppm; mild laryngitis in 2 males rats of the 800 ppm -group. No lesions observable in the lower respiratory tract (trachea and lung). The biological significance of the mild vacuolization of the brain stem in two males of the 800 ppm group is not known. The NOEL of the nine days whole body vapour inhalation tests on rats was considered to be 200 ppm.