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Toxicological information

Repeated dose toxicity: inhalation

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Administrative data

short-term repeated dose toxicity: inhalation
Type of information:
experimental study
Adequacy of study:
key study
Study period:
no data
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Study well documented, meets generally accepted scientific principles, acceptable for assessment

Data source

Reference Type:
study report
Report date:

Materials and methods

Principles of method if other than guideline:
Method: Repeated Dose Inhalation Toxicity; see "Details on inhalation exposure"
GLP compliance:
Limit test:

Test material

Constituent 1
Chemical structure
Reference substance name:
EC Number:
EC Name:
Cas Number:
Molecular formula:
Details on test material:
Origin: Esso Research and Engineering Company, 31 March 1966, used as received
- test material was considered to be free from impurities

Test animals

other: Charles River Caesarian-derived
Details on test animals or test system and environmental conditions:
no further details

Administration / exposure

Route of administration:
inhalation: vapour
Type of inhalation exposure:
whole body
other: Air
Remarks on MMAD:
MMAD / GSD: not applicable (vapour)
Details on inhalation exposure:
- All exposures were conducted in 1000-liter stainless steel and glass exposure chambers. Air-flow through the chamber was maintained by a
positive pressure rotary pump located at the exhaust side of the chamber. The airflow rate was monitored by a rotameter
- System of generating particulates/aerosols: Vapor of isophorone were generated by metering the liquid into a positive pressure spray nozzle
with a infusion pump. Aerosol was introduced into a heated distilling flask. A heating mantle was used to maintain the flask at a temperature
adequate to vaporize the entering aerosol. Exposure conducted under semi-closed conditions, the total chamber
airflow was drawn through the vapor-generating flask prior to entry the chamber.
- Duration of test/exposure: 20 exposures of 6 hours each
- Type of exposure: inhalation
- Post exposure period: none
- Concentrations: nominal 250 mg/m3; daily analytical determination (208  mg/m3) may be less precise than nominal due to incomplete recovery
in  analysis
Analytical verification of doses or concentrations:
Details on analytical verification of doses or concentrations:
Analytical Concentration of the chamber was determined daily by analysis of samples with a Becklman BD spectrophotometer
Duration of treatment / exposure:
28 days
Frequency of treatment:
6 hours/day; 5 days/week
Doses / concentrationsopen allclose all
Doses / Concentrations:
250 mg/m3 air
nominal conc.
Doses / Concentrations:
208 +/- 10 mg/m3 air (corresponds to about 36 ppm)
analytical conc.
No. of animals per sex per dose:
10 females and 10 males
Control animals:
yes, concurrent vehicle
Details on study design:
Post-exposure period: none
Positive control:
no positive control


Observations and examinations performed and frequency:
- Clinical signs: at frequent intervals
- Mortality: at frequent intervals
- Body weight: at study initiation and termination
- Haematology: at study initiation and termination,    identical 50 % of animals of each group
Sacrifice and pathology:
- Macroscopic: brain, pituitary, trachea, thyroid, parathyroid, lungs,  heart, liver, spleen, stomach, small intestine, large intestine,  adrenals, 
kidneys, urinary bladder, gonads, femur 
- organ weights: lungs, liver, kidneys, adrenal, spleen - Microscopic: lungs, liver, kidneys, adrenal, spleen for three males and  three females of each 

Remark: no urinalysis
Other examinations:
no other examinations
STATISTICAL METHODS: performed on body and organ weights

Results and discussion

Results of examinations

Clinical signs:
effects observed, treatment-related
mortality observed, treatment-related
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:
effects observed, treatment-related
Clinical biochemistry findings:
effects observed, treatment-related
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:
no effects observed
Histopathological findings: neoplastic:
no effects observed
Details on results:
- Mortality and time to death: no mortalities
- Clinical signs: slight nasal bleeding on day 3, reddish-brown  discoloration of the fur surrounding the nasal regions on days 6 through 8
- Body weight gain: body weight only of male rats was significantly  reduced compared to control
- Haematology: differential blood count: increase of the percentage of  lymphocytes (pre-exposure: 81.6 and 80.2 % among males and females,  
resp.; postexposure: 84.6 and 86.0 %, resp.), decrease in the percentage  of segmented neutrophiles (pre-exposure: 17.4 and 18.2 % among males 
and  females, resp.; postexposure: 14.6 and 13.3 %, resp.).
- Organ weights: absolute and relative liver weight only of male rats  were significantly reduced compared to control
- Gross pathology: no clear-cut compound-related abnormalities
- Histopathology: no unequivocal change

Effect levels

Dose descriptor:
Effect level:
< 208 mg/m³ air
Basis for effect level:
other: changes in haematological parameters and reduced liver weights

Target system / organ toxicity

Critical effects observed:
not specified

Any other information on results incl. tables

Target Organs Effects:

M: body weight gain (reduced; abs. and rel. liver weight(reduced)

M+F: lymphocytes (increased); heamoglobin (increased); neutrophils (reduced)

Applicant's summary and conclusion

In this subacute inhalation study with rats nose irritation and blood and liver changes were observed. The No-Observed-Adverse-Effect-Concentration (NOAEC, rat, 28 days) is determined to be < 208 mg/m3.
Executive summary:

In this subacute inhalation study 10 male and 10 female young adult Charles River CD rats were exposed (whole body) to isophorone at air concentrations of 0 or 250 mg/m3, 6 hours/day, 5 days/week, for 4 weeks. Results of daily spectroscopic determinations indicated that the average daily exposure was 208 mg/m3. Body weights measurements and heamatological studies were made before exposure and after 4 weeks. The rats were killed and gross necropsy were performed. Organ weights were determined for lungs, liver, kidney, adrenals and spleen. Histological examination of those tissues were performed in three males and three females per group. The following effects were observed: transient nasal bleeding, increased percentages of lymphocytes, decreased percentages of neutrophils and increased heamoglobin concentration in males and females and significantly lower terminal body weights and significantly decreased absolute and relative liver weights of exposed males, compared with controls.

Therefore, under the conditions of this study the No-Observed-Adverse- Effect-Concentration (NOAEC, rats, 28 d) for rats is determined to be < 208 mg/m3 .