Propane-1,3-diol

Repeated dose toxicity: inhalation

Administrative data

Endpoint:

short-term repeated dose toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Remarks:

PDO from chemical process.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1998

Report date:

1998

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

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

Deviations:

yes

Remarks:

Only 9 days of exposure. Highest dose did not induce toxicity.

GLP compliance:

yes

Remarks:

Two deviations noted deemed not to affect study validity. The test substance was characterized at a non-GLP-compliant lab, and expired hematology analytical control material was used during clinical laboratory analyses.

Test material

Test material information

Constituent 1

Reference substance name:

Propane-1,3-diol

EC Number:

207-997-3

EC Name:

Propane-1,3-diol

Cas Number:

504-63-2

Molecular formula:

C3H8O2

IUPAC Name:

propane-1,3-diol

Details on test material:

- Name of test material (as cited in study report): 1,3-Propanediol
- Physical state: Colorless Liquid
- Analytical purity: 99.891%
- Stability under test conditions: The test substance appeared to be stable under the conditions of the study; no evidence of instability was observed.

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: 8 weeks
- Weight at study initiation: 235 to 272 grams
- Fasting period before study: No fasting period before the study
- Housing: Rats were housed either singly or in pairs in suspended, stainless steel, wire-mesh cages.
- Diet: PMI Nutrition International, Inc. Certified Rodent LabDiet 5002, ad libitum
- Water: Tap water from United Water Delaware, ad libitum
- Acclimation period: 6 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 23±1
- Humidity (%): 50±10
- Air changes (per hr): Air flow was 25 L/min.
- Photoperiod (hrs dark / hrs light): 12-hour dark/12-hour light

Administration / exposure

Route of administration:

other: inhalation: vapor/aerosol

Type of inhalation exposure:

nose only

Vehicle:

other: air

Remarks on MMAD:

MMAD / GSD: MMAD of the aerosol in the intermediate- and high-level concentrations chambers was 2.2 to 2.4 µm and >99% of the particles were less than 10 µm. The GSD was 1.6.

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Low-level chamber test atmospheres were generated by metering the liquid test substance into a glass, heated flask with a Harvard Apparatus model 22 Syringe Infusion Pump. Intermediate and high-level chamber test atmospheres were generated by metering the liquid test substance into a Spraying Systems nebulizer with a Harvard Apparatus model 22 Syringe Infusion Pump.
- Method of holding animals in test chamber: Individually restrained in polycarbonate cylinders with conical nose pieces.
- Source and rate of air: Preheated, houseline air - metered with a Brooks model 5850E mass flow controller
- Method of conditioning air: Airflow, temperature, and relative humidity were monitored continually with a Camile Inhalation Toxicology Automated Data System (CITADS) and recorded at 15-minute intervals during each exposure. Chamber oxygen concentration was targeted to at least 19% . Chamber oxygen concentration was measured with a Biosystems model 3100R Oxygen Analyzer and was recorded twice during each exposure.
- System of generating particulates/aerosols: Low-level chambers were generated by metering the liquid test substance into a glass, heated flask. Intermediate and high-level chambers were generated by metering the liquid test substance into a Spraying Systems nebulizer.
- Temperature, humidity, pressure in air chamber: Test chambers = 25 - 28°C, 36- 53% ,Control chamber = 27°C, 42 - 58%
- Air flow: 23 - 25 L/min
- Air change rate: 12 air changes per hour
- Method of particle size determination: Samples to determine particle size distribution (MMAD, GSD, and percent particles less than 1, 3, and 10 µm) were taken 2 times during the study from the intermediate and high-level chambers. Particle size distribution was determined with a Sierra Series 210 Cyclone Preseparator/Cascade Impactor and Sierra Series 110 Constant Flow Air Sampler. An attempt was made to collect a particle size sample from the low-level chamber, but due to the lack of an appreciable aerosol component, particle size calculations were unable to be performed.
- Treatment of exhaust air: Exhaust from each of the test chambers was discharged through a water-filled scrubber followed by an MSA charcoal/HEPA Filter cartridge prior to discharge into the fume hood.

TEST ATMOSPHERE
- Brief description of analytical method used: The atmospheric concentration of vapor was determined by gas chromatography. Aliquots of the impinger solution were injected on a Restek RTX-1 column in a Hewlett-Packard model 5890Z gas chromatograph equipped with a flame ionization detector. The atmospheric concentration of the vapor component was determined by comparing the detector response of the impinger samples to that of the liquid standards with the use of standard curves. Standards were prepared on a daily basis by the quantitative dilution of the test substance in ethanol. No evidence of test substance instability was observed using the methods of test atmosphere generation by gas chromatography.
- Samples taken from breathing zone: Yes

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Known volumes of chamber atmosphere were drawn from the breathing zone of the rats through a sampling train consisting of a preweighed Gelman glass fiber (Type A/E) filter followed by a single, midget, glass impinger that contained ethanol as the collection medium; impinger collection efficiency exceeded 99%. The filters were weighed on a Cahn model C-31 Microbalance. The atmospheric concentration of aerosol was calculated from the difference in the pre-and post-sampling filter weights divided by the volume of chamber atmosphere sampled.

The atmospheric concentration of vapor was determined by gas chromatography. Aliquots of the impinger solution were injected on a Restek TR-1 column in a Hewlett-Packard model 5890A gas chromatograph equipped with a flame ionization detector. The atmospheric concentration of the vapor component was determined by comparing the detector response of the impinger samples to that of liquid standards with the use of standard curves. Standards were prepared on a daily basis by the quantitative dilution of the test substance in ethanol.

Duration of treatment / exposure:

6 hours per day

Frequency of treatment:

9 exposures (excluding weekends) over a 2-week period

Doses / concentrations

Doses / concentrations 1

Doses / concentrations 2

No. of animals per sex per dose:

10 male rats/dose group. Five rats/group were sacrificed at the end of the exposure period. Five rats/group were given a 18-day recovery period

Control animals:

yes

Details on study design:

- Dose selection rationale: High concentration was selected on the basis of rangefinding exposures conducted during methods development. 6 Male rats exposed to 1700 mg/m3 for 5 to 6 hours per day for four days resulted in lung noise in several animals but no gross pathological findings.
- Rationale for animal assignment (if not random): Computerized, stratified, randomization program so that mean body weights per group were similar.

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes (Twice daily)

DETAILED CLINICAL OBSERVATIONS: Yes
- All rats were individually observed for clinical signs before and after each exposure. Group clinical observations were made during exposures. During the recovery period, all rats were observed daily.

BODY WEIGHT: Yes
- Time schedule for examinations: During the exposure phase of the study, all rats were weighed daily (except on weekends). During the recovery period, all remaining rats were weighed at least twice per week.

FOOD CONSUMPTION: No

FOOD EFFICIENCY: No

WATER CONSUMPTION: No

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: Yes
- Time schedule for collection of blood: On the day following the last exposure
- Anaesthetic used for blood collection: Yes - under light carbon dioxide anesthesia
- Animals fasted: Yes after an approximate 16-hour fast
- How many animals: 4 groups of 10 male rats
- Parameters examined. red blood cell count (RBC), white blood cell count (WBC), platelet count (PLT), hemoglobin concentration (HGB), hematocrit (HCT), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), neutrophil count (Neut), ban neutrophil count (Band), lymphocyte count (Lymph), atypical lymphocyte count (Alym), monocyte count (Mono), eosinophil count (Eosin), basophil count (Baso)

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: On the day following the last exposure
- Animals fasted: Yes after an approximate 16-hour fast
- How many animals: 4 groups of 10 male rats
- Parameters examined: alklaline phosphatase activity (ALP), alanine aminotransferase activity (ALT), aspartate aminotransferase activity (AST), sorbitol dehydrogenase (SDH), bilirubin concentration (BILRN), cholesterol concentration (CHOL), total protein concentration (TPROT), albumin concentration (ALBMN), globulin concentration (GLOBN), glucose concentration (GLUCO), urea nitrogen concentration (BUN), creatinine concentration (CREAT), phosphate concentration (PHOS), calcium concentration (CALC), sodium concentration (Na), potassium concentration (K), chloride concentration (Cl)

URINALYSIS: Yes
- Time schedule for collection of urine: One day prior to each bleeding time, an overnight (approximately 16-hour) urine specimen was collected.
- Metabolism cages used for collection of urine: No data
- Animals fasted: Yes after an approximate 16-hour fast
- Parameters examined: volume ( VOL), osmolality (OSMOL), urobilinogen (UROBL), pH, hemoglobin or occult blood (BLOOD), glucose, protein, bilirubin, ketone (acetoacetic acid)

NEUROBEHAVIOURAL EXAMINATION: No

Sacrifice and pathology:

GROSS PATHOLOGY: Yes. The liver, kidneys, lungs, and brain were weighed at necropsy. Each rat was given a complete gross examination and representative samples of the following tissues were saved: liver, kidneys, lungs, heart, spleen, thymus, brain (cerebrum, midbrain, cerebellum, medulla/pons), spinal cord (cervical, thoracic, lumbar), stomach, duodenum, jejunum, ileum, pancreas, cecum, colon, rectum, mesenteric lymph node, adrenal glands, sciatic nerve, thyroid gland, parathyroid glands, trachea, esophagus, pharynx/larynx, sternum (with bone marrow), eyes, urinary bladder, prostate, seminal vesicles, testes, epididymides, nose, and gross lesions. All tissues were fixed in 10% neutral buffered formalin except for eyes, testes, and epididymides which were fixed in Bouin's solution. All tissues from control and high-level rats sacrificed after the 9th exposure were examined microscopically.

HISTOPATHOLOGY: Yes
Nose, pharynx/larynx, lungs, liver, kidneys, testes, and gross lesions were processed and examined microscopically for the low- and intermediate-level groups after the last exposure and for the control and high-level groups after the recovery sacrifice. Processed tissues were embedded in paraffin, cut at a nominal thickness of five micrometers, stained with hematoxylin and eosin, and examined with a light microscope.

Statistics:

Descriptive statistics including mean, standard deviation, and standard error of the mean were used to summarize experimental data.

Parametric or nonparametric pairwise comparisons between test and control groups were used to analyze mean body weights, body weight gains, and clinical laboratory data. Levene's test for homogeneity of variances and the Shapiro-Wilk test for normality were performed to determine which pairwise method of analysis was used to analyze clinical pathology data. When the Shapiro-Wilk test was not significant, the data were analyzed by a one-way analysis of variance (ANOVA) and pairwise comparisons between test and control groups made with Dunnett's test. If the Shapiro-Wilk test was not significant but Levene's test was significant, a robust version of Dunnett's test was used. When the Shapiro-Wilk test was significant, the data were analyzed with the Kruskal-Wallis test and pairwise comparisons between test and control groups made with Dunn's test.

Mean final body weights, and mean absolute and relative (to body weight and to brain weight) organ weights were statistically analyzed with ANOVA. When the value of the F-statistic for differences among groups was significant, pairwise comparisons between treated and control groups were made with Dunnett's test.

The Bartlett's test for homogeneity of variances was performed on organ weight data, and, if significant, was followed by nonparametric procedures.

Final body weights were used for determination of organ to body weight ratios. These body weights, determined just prior to necropsy, were not used to assess the effects of the test substance on body weights ( in-life data was used for this purpose).

Except for the Bartlett's test (p < 0.005), all significance was judged at p < 0.05.

Results and discussion

Results of examinations

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

no effects observed

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

Description (incidence and severity):

No compound-related hematology changes occurred during this study. Some statistically significant hematology findings occurred, but they were considered not to be compound-related for the following reasons: 1) decreased hemoglobin in the high level recovery group was small and similar changes were not present in groups sacrificed at the end of the exposure period, 2) a statistically significant decrease in MCH in the low level group sacrificed at the end of exposure was very small, did not occur in a dose-related manner, and was not associated with compound-related changes in any other hematology parameter, and 3) a statistically significant increase in PLT in the high level recovery group was very small, and a similar change was not present in any treated group sacrificed at the end of the exposure period.

Clinical biochemistry findings:

no effects observed

Description (incidence and severity):

No compound-related clinical chemistry changes occurred during this study. Some statistically significant clinical chemistry findings occurred, but they were considered not to be compound-related for the following reasons: 1) decreased SDH in the high level was not considered relevant as it is increases in this enzyme that are biologically important, 2) decreases in ALB, and the associated decreases in TP, in the intermediate and high level recovery groups were small and not associated with similar changes in treated groups sacrificed at the end of the exposure period, 3) and increases in Cl in all treated groups sacrificed at the end of the exposure period, and in the intermediate and high level recovery groups, were small, not dose-related, and not associated with changes in other electrolytes.

Urinalysis findings:

no effects observed

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Description (incidence and severity):

Results of Bartlett's test indicated that parametric procedures were appropriate for analysis of all organs weighed. No statistically or biologically significant changes in organ weight occurred in rats exposed to the test substance.

Gross pathological findings:

no effects observed

Description (incidence and severity):

No gross changes attributable to exposure to the test substance were observed in study rats. Gross observations noted for rats were nonspecific and incidental and are routinely observed in rats of this strain and age.

Histopathological findings: non-neoplastic:

no effects observed

Description (incidence and severity):

Microscopic observations noted for rats were nonspecific and incidental and are routinely observed in rats of this strain and age.

Effect levels

Dose descriptor:

NOEL

Effect level:

1 800 mg/m³ air (analytical)

Sex:

male

Remarks on result:

other: highest concentration tested

Target system / organ toxicity

Critical effects observed:

no

Any other information on results incl. tables

The analytically determined mean concentrations as measured in the exposure chambers were:

41 ± 1.7 mg/m3

650 ± 8.6 mg/m3

1800 ± 27 mg/m3

Applicant's summary and conclusion

Conclusions:

There were no test substance-related mortalities in the study. No toxicologically important changes in clinical pathology, pathology, or in-life animal measurement parameters occurred in any group. The no-observed-effect level (NOEL) for this study is defined as the highest dose at which toxicologically adverse effects attributed to the test substance were not detected. Under the conditions of this study, the NOEL for repeated inhalation exposure in male rats was considered to be 1800 mg/m3, the highest concentration tested.

Executive summary:

Three groups of 10 male rats each were exposed by inhalation to either vapor or a vapor/aerosol mixture of the test substance in air at concentrations targeted to 60, 600, or 1800 mg/m³ for 6 hours/day, 4 or 5 days/week for a total of 9 exposures. A procedural control group of 10 male rats was simultaneously to air only. Rats were weighed prior to each exposure and were observed for clinical signs prior to, during, and following each exposure. At the end of the exposure period, clinical pathology evaluations were conducted on 10 rats/group, and 5 rats/group were sacrificed and necropsied. At the end of the 18-day recovery period, the 5 surviving rats/group were given clinical pathology examinations, then sacrificed and necropsied. All rat were examined for gross and microscopic changes.

 

The analytically determined concentrations were 41, 650, and 1800 mg/m³ over the duration of the study. All rats survived to the termination of the study and were sacrificed by design. There were no test substance-related clinical signs of toxicity observed during the study. No statistically significant body weight differences were observed in any group. There were no compound-related adverse effects noted during clinical pathology or pathology evaluations. The no observed adverse effect level (NOAEL) was considered to be 1800 mg/m³.