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Repeated dose toxicity: inhalation

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Administrative data

sub-chronic toxicity: inhalation
other: 90-day repeated dose
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Study period:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Comparable to a guideline study.

Data source

Reference Type:
study report
Report Date:

Materials and methods

Test guideline
equivalent or similar to
OECD Guideline 413 (Subchronic Inhalation Toxicity: 90-Day Study)
GLP compliance:
yes (incl. certificate)
Limit test:

Test material

Details on test material:
- Name of test material (as cited in study report): Ethoxypropanol
- Physical state: Liquid
- Analytical purity: 93 %
- Impurities (identity and concentrations):
7% 2-ethoxy-1-propanol
- Purity test date: 2 April 1985
- Lot/batch No.: GOHC Sample No. 958
- Expiration date of radiochemical substance (if radiolabelling):
- Stability under test conditions: Samples of the test substance analyzed throughout the study period by GC-MS and IR spectroscopy gave similar results.
- Storage condition of test material: Ambient conditions. Drums were flushed with nitrogen when aliquots were removed for use.

Test animals

Details on test animals and environmental conditions:
Animals were uniquely identified by numbers tattooed into the ears. In addition, ear punching identified animals with numbers in excess of 99.

- Source: Charles River UK Ltd.
- Age at study initiation: Approximately 6-7 weeks old when received on 27 March. The first exposures occurred on 8 April.
Group mean body weight at initiation of exposures:
Males – 243 to 248 g
Females – 180 to 186 g
- Housing: Except during exposures, the rats were kept, 5 of the same sex per cage, in suspended polypropylene holding cages with stainless steel mesh tops and floors. Plastic trays, lined with absorbent paper were placed below the cages. The paper was changed daily. Clean cages were introduced at intervals throughout the study.
The rats were kept in a single room and once exposures began, the cages for rats in each group were positioned on individual cage batteries. These were kept in isolated ventilated areas within the same room to avoid the possibility of inhalation of the test material from the fur of rats in other groups.
- Diet: While in their cages, rats had access to a weighed quantity of a standard quality controlled laboratory rat food (Labsure LAD 1).
- Water: Tap water was available from polypropylene bottles at all times when the rats were in the cages. Water bottles were rinsed and refilled daily, and thoroughly cleaned at intervals during the study.
- Acclimation period: 11 days.

- Temperature: Holding room: 18 – 26 degrees C
- Humidity: Holding room: 36 – 64 % relative humidity
- Photoperiod: Lighting was controlled to give 12 hours light (0800 – 2000) and 12 hours dark during each 24 hours.

Fist exposure – 8 April 1985
Final necropsy – 5 August 1985

Administration / exposure

Route of administration:
inhalation: vapour
Type of inhalation exposure:
whole body
other: unchanged (no vehicle)
Remarks on MMAD:
MMAD / GSD: Weekly counts of the number of particles in a 1 minute sample of chamber atmospheres were estimated using an optical particle monitor. Particles found were all less than 5 um in diameter. As the chamber concentrations were well below the saturated vapour concentrations it was considered unlikely that these particles were droplets of test material.
Details on inhalation exposure:
- Exposure apparatus: The vapour was produced by metering the liquid to a stainless steel concentric jet atomizer and passing the aerosol into a glass column in which it evaporated. To facilitate vaporisation, at the high dose air to the atomizer was passed through a water bath maintained at 75 degrees C. The vapour passed through the vertical glass column into the chamber inlet duct.The exposure chambers were constructed from stainless steel and glass and were approximately 500 liters internal volume. The chambers were of square cross section and fitted with a squat pyramidal base and top. An H-shaped extraction plenum was fitted in the base of the chambers.
- Method of holding animals in test chamber: During exposures the rats were housed in stainless steel wire mesh cages, which were supported on two mesh shelves. The position of male and female animals were alternated on these shelves each day
- Source and rate of air: Dry, oil-free, compressed air was passed to the annulus of the atomizer tip at a pressure of 40-50 psi. This produced a flow to the atomizer tip of approximately 10 liters per minute.
- Temperature, humidity, pressure in air chamber: Air temperature, relative humidity and air pressure in each exposure chamber were monitored continuously and recorded at approximately 30 minute (pressure) or hourly intervals (temp, humidity) throughout each exposure.
Chamber temperatures during exposure were similar for all groups.
Relative humidity tended to be higher in the high dose chamber.
- Air flow rate: Total volume flow to the exposure chambers was 90 litres per minute. The airflow into each chamber was monitored continuously using tapered-tube flowmeters and was recorded at approximately hourly intervals throughout each exposure.
-Treatment of air: The chamber atmosphere was extracted by means of individual air handling units fitted with filters. The extract flow was adjusted by means of a gate valve so as to maintain the chamber pressure approximately 3 mm of water below that of the surrounding room.

- Brief description of analytical method used: After 6 hours exposure, the syringe pumps were switched off. The volume of test material remaining in each syringe and any ‘run-off’ from the glass column was recorded and the volume used during the exposure calculated.
In addition, the concentration of ethoxypropanol present in the exposure chambers was determined at hourly intervals during each exposure. Samples of the test atmosphere were withdrawn through a gas absorption tube and the amount of ethoxypropanol in these samples determined by thermal desorption methods.
- Samples taken from breathing zone: yes
Sampling was performed to determine the spatial distribution of ethoxypropanol within the chambers. Results indicated that distribution of the test substance in the exposure chamber was adequately uniform.
Analytical verification of doses or concentrations:
Duration of treatment / exposure:
6 hours per day for 13 weeks. Exposures were shortened on days during which urine and blood samples were taken (Week 1 and Week 12).

Ten male and ten female rats from the control and high dose groups were maintained for 4 weeks, without exposure, following termination of exposures.
Frequency of treatment:
5 days each week
Doses / concentrationsopen allclose all
Doses / Concentrations:
0, 0.425, 1.275, 8.5 mg/l
other: target concentration
Doses / Concentrations:
0, 0.624, 1.658, 11.19 mg/l
nominal conc.
Doses / Concentrations:
0, 0.426, 1.266, 8.36 mg/l
analytical conc.
No. of animals per sex per dose:
Controls and high dose groups: 25 males and 25 females Low and mid dose groups: 15 males and 15 females
Control animals:
yes, sham-exposed
Details on study design:
- Dose selection rationale: Approximately equal group mean body weights at study initiation.
- Post-exposure recovery period in satellite groups: 4 weeks

Group Mean Conc of Ethoyxpropanol Vapour (mg/l)
Target Measured Nominal

1 (control) 0
2 (low) 0.425 (100 ppm) 0.426 0.614
3 (mid) 1.275 (300 ppm) 1.266 1.658
4 (high) 8.5 (2000 ppm) 8.36 11.19


Observations and examinations performed and frequency:
- Time schedule: At least twice daily and during exposure.

- Time schedule: Weekly

- Time schedule for examinations: Initially for allocation to exposure groups, 1 week prior to start of exposures, on the first day of exposure, at weekly intervals thereafter, and at study termination.

- Other: The quantity of food consumed by each cage of 5 rats was recorded commencing 1 week before the start of exposures and weekly thereafter.

- Other: The quantity of water consumed by each cage of rats was recorded daily commencing one week before the start of exposures and weekly thereafter.

- Time schedule for examinations: Once pre-exposure and during Week 12.
- Dose groups that were examined: All animals

- Time schedule for collection of blood: Prior to exposure and during Weeks 1 and 12
- Anaesthetic used for blood collection: Yes
- Animals fasted: Yes
- How many animals: 5 males and 5 females per group: pre-exposure and Week 1
10 males and 10 females per group: Week 12
- Parameters checked in table [No.?] were examined: Packed cell volume (PCV), haemoglobin (Hb), red cell count (RBC), mean corpuscular haemoglobin concentration (MCHC), mean corpuscular volume (MCV), total white cell count (WBC total) and differential count (Diff), platelet count (Plts), thrombotest (TT), reticulocyte count (Retic).

- Time schedule for collection of blood: Prior to exposure and during Weeks 1 and 12
- Animals fasted: Yes
- How many animals:
5 males and 5 females per group: pre-exposure and Week 1
10 males and 10 females per group: Week 12
- Parameters checked in table [No.?] were examined: Glucose, total protein, albumin, globulin, albumin/globulin ration (A/G), urea nitrogen, creatinine, alkaline phosphatase (AP), glutamic-pyruvic transaminase (GPT), glutamic-oxaloacetic transaminase (GOT), gamma glutamyl transferase (gamma GT), ornithine carbamoyltransferase (OCT), total bilirubin, sodium (Na), potassium (K), calcium (Ca), inorganic phosphorus (P), chloride (Cl), cholesterol (Chol).

- Time schedule for collection of urine: Prior to exposure and during Weeks 1 and 12
- Metabolism cages used for collection of urine: Yes
- Animals fasted: Yes
- Parameters checked in table [No.?] were examined: Volume, colour, pH, osmolality, protein, total reducing substances, glucose, ketones, bile pigments, urobilinogen, haem pigments, microscopy.

Sacrifice and pathology:
-The macroscopic appearance of all tissues was noted.

-H&E sections were examined as follows: All tissues from ten male and ten female rats from the control and high dose groups sacrificed at the end of exposure.

The following tissues were preserved in 10% neutral buffered formalin (except eyes which were preserved in Davidson's fixative) and examined:
-Nasal passage, tongue, pharynx, larynx, trachea, lungs & bronchi, heart, aorta, oesophagus, stomach (glandular and non-glandular), duodenum, jejunum, ileum, caecum, colon, rectum, kidneys, urinary bladder, testes, epididymides, seminal vesicle, prostate, ovaries, uterus, liver, spleen, pancreas, salivary glands, thymus, thyroids, adrenals, lymph nodes(tracheaobronchial, cervical, axillary), brain(sections of medulla/pons, cerebellar cortex and cerebral cortex), pituitary, eyes, sciatic nerve, sternum(for bone marrow), spinal cord, muscle(thigh), skin, mammary gland, femur, remaining head, all gross lesions.

All tissues observed to be macroscopically abnormal.
Lungs of all control and high dose rats in the withdrawal phase.
Lungs of 10 male and 10 female low- and mid-dose rats sacrificed at the end of exposure.
Other examinations:
The following organs were dissected free and weighed from each animal: adrenals, kidneys, liver, brain, spleen, lungs, thymus, testes, heart, pituitary.
The following statistical tests were used to analyze bodyweight, food and water consumption, organ weight and clinical pathology data: Bartlett’s test for heterogeneity of variance between treatments; followed by a one-way analysis of variance (no significant heterogeneity or satisfactory transformation identified) and Student’s ‘t’ test and Williams’ test; or the Kruskel-Wallis analysis of ranks (significant heterogeneity that could not be removed by a transformation) and non-parametric equivalents of the ‘t’ test and Williams’ test.
Food and water consumption was analyzed on a cage basis
Where appropriate, analysis of covariance was used in place of analyses of variance.

Results and discussion

Results of examinations

Clinical signs:
effects observed, treatment-related
mortality observed, treatment-related
Body weight and weight changes:
no effects observed
Food consumption and compound intake (if feeding study):
effects observed, treatment-related
Water consumption and compound intake (if drinking water study):
effects observed, treatment-related
Ophthalmological findings:
no effects observed
Haematological findings:
no effects observed
Clinical biochemistry findings:
no effects observed
Urinalysis findings:
effects observed, treatment-related
Behaviour (functional findings):
not examined
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Gross pathological findings:
effects observed, treatment-related
Histopathological findings: non-neoplastic:
no effects observed
Details on results:
One female rat in the mid-dose group was found dead during Week 5. Clinical signs indicative of an irritation were observed in the high dose animals only. A reduced ‘startle response’ was also noted in the high dose animals during exposure.

No treatment-related effects were seen.

Minimal increases in food intake was noted for male rats in the mid- and high-dose groups.

Minimal increases in the amount of water consumed were noted in the high dose animals.

No treatment-related defects were seen.

No treatment-related effects were seen.

Increased OCT values were seen in three high-dose male rats during Week 1 compared to control values. Only one of these values was above the laboratory’s upper normal limit, and the group mean was within the normal range.

Increases in urine volume were noted for high dose animals during Weeks 1 and 12, and for mid-dose animals during Week 12. Decreased urine pH was noted in high-dose male rats during Weeks 1 and 12. These findings were not accompanies by serum changes or microscopic pathology indicative of a toxic effect.

Reduced startle response.

There was evidence of a slight increase in liver weights in the high dose female rats. This is consistent with liver enlargement reported in previous studies of ethoxypropanol.

An increased incidence of pale foci in the lungs was noted in mid- and high-dose animals at the end of the exposure period, as well as in high dose animals retained through the recovery period.

Slightly increased incidence of focal, minimal macrophage aggregation in high dose animals only. This finding is regarded as a normal physiological response to inhaled particles and was also seen among control animals. It is therefore not considered to be toxicologically significant.

Effect levels

Dose descriptor:
Effect level:
>= 1.266 mg/L air (analytical)
Based on:
test mat.
Basis for effect level:
other: overall effects clinical signs; organ weights

Target system / organ toxicity

Critical effects observed:
not specified

Applicant's summary and conclusion

90-day inhalation NOAEC in rats is equal to or greater than 1.266 mg/l.
Executive summary:

In a guideline and GLP 90-day whole-body inhalation study in rats, exposure to ethoxypropanol vapour (the in vivo hydrolysis product of ethoxypropyl acetate) at a concentrations of up to 8.36 mg/l for 6 hours per day, 5 days per week, for 13 weeks resulted in clinical signs indicative of irritant properties, and reduced ‘startle response’ during exposure. Increases in liver weight were also noted in female rats exposed at the 8.36 mg/l exposure level.  Animals exposed at concentrations of 1.266 or 0.426 mg/l did not exhibit any evidence of adverse effects (clinical signs, body weight, food and water consumption, opthalmoscopy, haematology, blood chemistry, urinalysis, organ weights, gross or microscopic pathology).  On the basis of these findings 1.266 mg/l is considered to be a subchronic NOAEC for ethoxypropanol vapour under the conditions of this study. On a molar basis, this would be equivalent to a dose of 1.812mg/l of ethoxypropyl acetate