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Toxicological information

Repeated dose toxicity: inhalation

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Administrative data

sub-chronic toxicity: inhalation
Type of information:
experimental study
Adequacy of study:
key study
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Study published in peer-reviewed literature, minor restrictions in reporting, but otherwise acceptable for assessment.

Data source

Reference Type:
Subchronic nose-only inhalation study of propylene glycol in Sprague-Dawley rats
Suber RL, Deskin R, Nikiforov I, Fouillet X, Coggins CR
Bibliographic source:
Fd. Chem. Toxic. 27, 573-583.

Materials and methods

Principles of method if other than guideline:
Groups of 19 male and female rats were exposed by inhalation to 0.0, 0.16, 1.0 and 2.2 mg/l air propylene glycol for 6 hr/day, 5 days/week for 90 days. The clinical signs, body weights, food consumption, haematological parameters, clinical chemistry and gross and histopathological examinations were performed.
GLP compliance:
not specified
Limit test:

Test material

Constituent 1
Chemical structure
Reference substance name:
EC Number:
EC Name:
Cas Number:
Molecular formula:
Details on test material:
- Name of test material (as cited in study report): propylene glycol, USP
- Analytical purity: > 99%
- Storage condition of test material: at 20 to 23 °C and 50% relative humidity
- Supplier: Dow Chemical SA, Geneva, Switzerland

Test animals

Details on test animals or test system and environmental conditions:
- Source: IFFA-CREDO, L'Arbresle, France
- Age at study initiation: 3 months
- Weight at study initiation: males 355-365 g, females 255-265 g
- Housing: 2 per cage, Macrolon Type III cages
- Diet: pelleted feed (Specia Diet Services Rat and Mous No. 1, Shell Diet Services, Engand), ad libitum, except during the exposure
- Water: tap water, ad libitum
- Acclimation period: 10 days

- Temperature (°C): 22 ± 3
- Humidity (%): 30-70
- Photoperiod (hrs dark / hrs light): 12 / 12

Administration / exposure

Route of administration:
Type of inhalation exposure:
nose only
other: air
Remarks on MMAD:
MMAD / GSD: The MMADs of the diluted aerosol were less than2.22 and 1.96 µm for the medium- and high-concentration groups, respectively. The mean geometric diameter for the low-concentration group was not obtainable, possibly due to evaporation which occurred with large quantities of dilution air. No measurements were made of the particle size of the undiluted aerosol. The geometric standard deviations were 1.44 and 1,57, respectively for the medium- and high-dose groups.
Details on inhalation exposure:
- Exposure apparatus: Battelle nose-only exposure chambers
- System of generating particulates/aerosols: Battelle-designed nebulizers
- Air flow rate: 35-50 litre/minute

- Brief description of analytical method used: Gas chromatogarphy
- Samples taken from breathing zone: yes
Analytical verification of doses or concentrations:
Details on analytical verification of doses or concentrations:
The aerosol concentrations were measured once per day by samples taken at animal ports with two gas washbottles (Aver & Co. AG, cat. No. 30852) in series, each containing l00 ml distilled water. Samples were routinely taken for about l0 min for the high, 30 min for the medium and 120 min for the low concentration. The air flow rates for sample collection were nominally 2 litre/min. During sampling, volumes were measured by calibrated
dry gasmeters (Compagnie des Compteurs, model G Ló, No. 160 525). Also, sampling flow-rates were obtained from calibrated rotameters. After
sampling, the contents of each washbottle were poured into a 150-ml volumetric flask, the sampling bottle was rinsed with distilled water and the flask was brought to volume. Samples were analysed daily for propylene glycol concentration by gas chromatography. The particle concentration was monitored continuously throughout exposures for the high concentration group. A dilution system (10;1) in connection with a Mini-RAM (GCA Corp., Bedford, MA) aerosol monitor was used. The Mini-RAM was calibrated against gravimetric measurements. The particle size distributions of the propylene glycol aerosol were determined once a week for each exposure group using a Mercer seven-stage cascade impactor (Model 02-100: IN-TOX Products, Albuquerque, NM). Isokinetic samples were taken at a flow-rate of I litre/min directly from an animal port for each exposure group, Impactor stages were weighed using a Mettler microbalance (Model AJ, Mettler, Zurich, Switzerland) with a sensitivity of 0.1 µg. The effective cutoff aerodynamic diameter (ECAD) values for lhe seven stages were: 0.325, 0.715, 1.06, 1.60,2.13,3.0 and 4.6 µm. Particle size distribution parameters (Raabe, l97l) were determined from the weight of material collected on each stage of the cascade impactor. The data were fltted using a probit model and the mass median aerodynamic diameter (MMAD) and geometric standard deviation were determined.
Duration of treatment / exposure:
90 days
Frequency of treatment:
6 hours/day, 5 days/week
Doses / concentrationsopen allclose all
Doses / Concentrations:
0, 160, 1000, 2200 mg/m3
nominal conc.
Doses / Concentrations:
0, 0.16 ± 0.04, 1.01 ± 0.11 and 2.18 ± 0.31 mg/l
analytical conc.
No. of animals per sex per dose:
Control animals:
yes, sham-exposed


Observations and examinations performed and frequency:



- Time schedule for collection of blood: before starting exposures and before autopsy. The pre-study measurements were carried out over 4 days, 36 or 40 animals which comprised equal numbers of males and females were retro-orbitally bled each day. the measurements at the end of the study were carried out over 3 days. About 50 animals (approximately equal numbers of males and females from each treatment group) were retro-orbitally bled on each day of killing.
- Anaesthetic used for blood collection: Yes (carbon dioxide)
- How many animals: all animals
- Parameters examined: haematocrit, haemoglobin concentration, red blood cell count, white blood cell count, mean read blood cell count, mean red blod cell corpuscular haemoglobin, mean corpuscular haemoglobin concentration and platelets.

before starting exposures and before autopsy. The pre-study measurements were carried out over 4 days, 36 or 40 animals which comprised equal numbers of males and females were retro-orbitally bled each day. the measurements at the end of the study were carried out over 3 days. About 50 animals (approximately equal numbers of males and females from each treatment group) were retro-orbitally bled on each day of killing.
- Anaesthetic used for blood collection: Yes (carbon dioxide)
- How many animals: all animals
- Parameters examined: serum concentrations of glucose, urea nitrogen, total protein, albumin, total bilirubin, total cholesterol, calcium, inorganic phosphate, chloride, alkaline phosphatase, ¿-glutamyltransferase, alanine aminotransferase, serum creatinine, 5'-nucleotidase, sorbitol dehydrogenase, sodium, potassium, creatine phosphokinase, triglycerides and total phospholipids.

Sacrifice and pathology:
Other examinations:
Respiratory rates and tidal volumes were measured in four rats/group/sex on study day 7, and repeated on the same animals on study days 42 and 84. Four animals were measured simultaneously for 15 min preceding exposure and for the first 30 min of exposure while in exposure/plethysmograph tubes (Coggins et al., l98l).
Statistical analyses were conducted by one-way analysis of variance, Bartlett's tests for homogeneity, Dunnett's test for significance or a modified r-test (Gad and Weil, 1982).

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):
effects observed, treatment-related
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:
not examined
Behaviour (functional findings):
not examined
Organ weight findings including organ / body weight ratios:
no effects observed
Gross pathological findings:
no effects observed
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Histopathological findings: neoplastic:
no effects observed
Details on results:
There were no significant differences in respiratory rates, tidal volumes or minute volumes between the control group and any of the treatment groups' nor did respiratory rates within groups decrease as the animals became acclimatized to the nose-only exposure conditions.
A treatment-related effect was reported nasal haemorrhaging which began during the second week of exposure and persisted throughout the study; recovery from clinical signs of nasal haemorrhaging occurred during the non-exposure weekend periods. This haemorrhaging was reduced to less than 4% in the low-exposure female group after the fourth week of exposure. From week 2 to 13, the average incidences of nasal haemorrhaging in males were less than 1% in controls, 64% in the low-exposure group, 74% in the medium-exposure group and 75% in the high exposure group. In females, the average incidences were less than 1% in controls, l4% in the low exposure group and 7l% in the medium- and high exþosure groups. Similar trends were observed for ocular discharge, with incidences of 16% in low exposure males, 40% in medium- and high-exposure males, and 570 in controls. There was generally less ocular discharge in females, who had incidences of 8% in controls, l4% in the low exposure group, 28% in the medium-exposure group and 35% in the high exposure group.

The high-exposure female rats showed a significant reduction in body weight, approximately 5-7%,starting on day 50 and continuing until the end ofthe study. The medium-exposure females also had reduced body weights beginning on study day 64 which continued until the end of the study. There were no signiflcant differences between the body weights of control and treated males; however, a trend was established by day 56; the control animals were heaviest, the low-exposure group were lighter than the medium-exposure group and the high-exposure group were the lightest. The differences between the control and high-exposure mean body weights were only 4%o for males and 6% for females on the flnal day of the study. The sudden drop in body weight for the final day of the study was due to a 6-hr fast; the animals were weighed after the flnal exposure. On previous weighings, the animals were weighed before they were placed in the nose-only chambers.

The reduction in the females body weights during the study was correlated with a significant reduction in feed consumption beginning on study day 43 for the high-exposure females and on study day 50 for the medium-exposure females. The mean feed consumption was also significantly reduced on study day 50 for the low-exposure females. High-exposure male rats had significantly reduced feed consumption on study days 57, 64 and 88. There were no trends or significant differences from the controls in feed consumption for the low-exposure or medium-exposure male rats.

Pre-study measurements of selected haematology components revealed statistically significant (P < 0.05) diflerences between animals assigned to
treated groups and control groups. However, the changes showed no consistent trends with respect to treatment group or sex and were not considered to be biologically significant.
The only statistically significant change in the erythrocytic profile at the end of the study occurred in the high-exposure females. The mean corpuscular haemoglobin concentration was reduced when compared with that lor the female control group. There were significant decreases in white blood cell count, banded neutrophil count and lymphocyte count in medium- and high-exposure females. High-exposure male rats also showed a significantly reduced banded neutrophil count which was not considered relevant to propylene glycol exposure.

There were no statistically signiflcant changes in pre-study concentrations of serum enzymes, serum chemistries or serum electrolytes in the male rats. In the pre-study only serum phosphate was significantly increased (P < 0.05) in females of the high-exposure group (2.84 + 0.48 mmol/litre) compared with the control group (2.49 + 0.40 mmol/litre).
There were statistically significant decreases in serum sorbitol dehydrogenase and ¿-glutamyl transferase in the medium- and high-exposure male rats, respectively. Sporadic statistically significant changes also were reported for serum glucose, albumin and creatinine in medium-exposure males and for serum protein, albumin and cholesterol in high-exposure males. In the female rats, serum protein was elevated only in the medium-exposure
animals. There were no changes in serum electrolytes in males of any group but serum chloride was elevated in the low-exposure females. As propylene glycol levels increased, decreasing trends in serum aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase and ¿-glutamyl
transferase, serum protein, albumin, cholesterol and inorganic phosphate were observed in male rats, but were not observed in the female rats.

Absolute organ weights were significantly decreased for the lungs of high-exposure females, spleens of low- and high-exposure males, livers of
medium- and high-exposure males, kidneys of highand medium-exposure males and females. Lung weights were signiflcantly increased in low-exposure males. When organ weights were expressed relative to terminal body weights or brain weights, high-exposure male spleen weights were signiflcantly decreased and low-exposure male lung weights remained increased. There were no significant changes in absolute weights of adrenal glands, testes, brain, thymus, heart, prostate, uterus, urinary bladder or ovaries nor in these organ weights when expressed relative to body or brain weight.

There were no treatment-related changes in gross pathology when the animals were killed.

Microscopic evaluation of the nasal cavity revealed a thickening of the respiratory epithelium, noted as an increase in the numbers of goblet cells or as an increase in the mucin content of the goblet cells in the medium and high-exposure male and female rats. The increased number of goblet cells was observed in the posterior portion of the nasal cavity, lining of the septum, the lateral walls, the anterior turbinates and in selected cases the ethmoid turbinates. The subjective judgement of the proliferation of goblet cells in the posterior nasal cabity was accompanied by an increased volume of mucus in the individual goblet cells. There were no histological changes in the trachea, lungs or larynx.

Effect levels

open allclose all
Dose descriptor:
Effect level:
1 000 mg/m³ air
Basis for effect level:
other: Based on the decreased body weights of the high-dose females
Dose descriptor:
Effect level:
2 200 mg/m³ air
Basis for effect level:
other: No adverse effects observed at the highest tested dose.
Dose descriptor:
Effect level:
160 mg/m³ air
Basis for effect level:
other: Based on reported nasal haemorrhaging in all test groups

Target system / organ toxicity

Critical effects observed:
not specified

Applicant's summary and conclusion