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Repeated dose toxicity: inhalation

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Administrative data

Endpoint:
chronic toxicity: inhalation
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1998
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: This study was conducted in accordance with GLP and OECD guideline 453 and TSCA guideline part 798

Data source

Referenceopen allclose all

Reference Type:
study report
Title:
Unnamed
Year:
1998
Report Date:
1998
Reference Type:
publication
Title:
Propylene glycol monomethyl ether (PGME): Inhalation toxicity, carcinogenicity and mode of action in Fischer 344 rats B6C3F1 mice
Author:
Spencer, P.J., Crissman, J.W. et al
Year:
2002
Bibliographic source:
Toxicol. Path. In press.

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 453 (Combined Chronic Toxicity / Carcinogenicity Studies)
Qualifier:
according to
Guideline:
other: TSCA Guideline Part 798
Principles of method if other than guideline:
Method: other: OECD 453
GLP compliance:
yes
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): propylene glycol monomethyl ether
- Molecular formula (if other than submission substance): C4H10O2
- Molecular weight : 90.12
- Physical state: Clear colorless liquid
- Analytical purity: 97.39 % - 97.42 %:
- Lot/batch No.: QP 911113-45D3
- Vapor pressure; 12.5 mm Hg@25°C
- Vapor density: 3.12
- Flash point: 32°C
- Boiling point: 120.2°C
- Specific gravity: 0.917 @ 25/25°C

Test animals

Species:
rat
Strain:
Fischer 344
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River breeding Laboratories, Inc., Kingston, NY
- Age at study initiation: Approximately 6-7 weeks
- Weight at study initiation: Approximately 140-150 gms (male) and 110-120 - gms (female)
- Fasting period before study: None
- Housing: 2/cage in stainless steel wire cages
- Diet (ad libitum): Except during exposure
- Water (ad libitum): Except during exposure
- Acclimation period: 1 week


ENVIRONMENTAL CONDITIONS
- Temperature (°C): Standard conditions
- Humidity (%): Standard conditions
- Air changes (per hr): Standard conditions



Administration / exposure

Route of administration:
inhalation: vapour
Type of inhalation exposure:
whole body
Vehicle:
other: unchanged (no vehicle)
Details on inhalation exposure:
See the attachment-1
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
See the attachment-1
Duration of treatment / exposure:
2 years whole body exposure
Frequency of treatment:
6 hours/day, 5 days/week
Doses / concentrationsopen allclose all
Remarks:
Doses / Concentrations:
300 ppm
Basis:
nominal conc.
Remarks:
Doses / Concentrations:
1000 ppm
Basis:
nominal conc.
Remarks:
Doses / Concentrations:
3000 ppm
Basis:
nominal conc.
No. of animals per sex per dose:
50 animals/sex/dose
Control animals:
yes
Details on study design:
See the attachment-1

Examinations

Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Daily (except weekends) for signs of toxicity and checked daily for mortality (including weekends)

DETAILED CLINICAL OBSERVATIONS: Yes
These observation were made only rats belonging to group A
- Time schedule: Prior to start of exposure and weekly thereafter


BODY WEIGHT: Yes
- Time schedule for examinations: All animals were weighed prior to the initial exposure and weekly intervals for the first 13 weeks and at approximately 4- weeks thereafter.

OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations:
- Dose groups that were examined: Prior to start of exposure and prior to necropsy in all animals dose group A.


HAEMATOLOGY: Yes
- Time schedule for collection of blood: After 6 months, 12 months and 18 months of exposure
- Anesthetic used for blood collection: Yes (identity) Methoxyflurane
- Animals fasted: Yes
- How many animals: For interim collection (6, 12, 18 months) 10 rats/sex/exposure randomly selected
- Parameters checked in table [No.?] were examined.


CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: After 6 months, 12 months and 18 months of exposure
- Anesthetic used for blood collection: Yes (identity) Methoxyflurane
- Animals fasted: Yes
- How many animals: For interim collection (6, 12, 18 months) 10 rats/sex/exposure randomly selected
- Parameters checked in table [No.?] were examined.


URINALYSIS: Yes
- Time schedule for collection of urine: 1-6 days prior to 6, 12, 18 months blood collection and 1 day prior to 24 month blood collection
- Metabolism cages used for collection of urine: No
- Animals fasted: No
- Parameters checked in table [No.?] were examined.






Sacrifice and pathology:
GROSS PATHOLOGY: Yes
All surviving animals were fasted overnight and necropsied after approximately 24 months of exposure to PGME. Each animal was weighed, anesthetized with methoxyflurane and trachea exposed and clamped prior to decapitation. The eyes were visually examined throgh a moistened glass slide pressed against the corneal surface. Weight of brain, heart, lungs, liver, kidneys, adrenals and testes were recorded and the organ weights to final body weight ratios were calculated. The lungs were intratracheally infused to an approximately normal inspiratory volume with neutral phosphate buffered 10 % formalin. The nasal cavity was flushed by a similar method via the pharyngeal duct. Representative samples of tissues and any masses or lesions observed during necropsy were preserved in formalin. A similar procedure was followed for rats which died or were sacrificed in a moribund condition, except that blood samples, terminal body weights and organ weight data were not be collected.
HISTOPATHOLOGY: Yes
Tissues were prepared for light microscopic evaluation by procedures, sectioned at approximately 6µm and stained with hematoxylin and eosin. A complete histopathologic evaluation of all tissues was conducted on all control and 3000 ppm PGME exposure rats and from rats that died or were sacrificed in a moribund during the course of the study. In addition, microscopic examination of tissues from the low and middle exposure groups included the liver, kidneys, lungs, nasal tissues and all gross lesions.
Other examinations:
Organ weights: Weight of brain, heart, lungs, liver, kidneys, adrenals and testes were recorded.
Statistics:
See the attchment-1

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 examined
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
no effects observed
Haematological findings:
no effects observed
Clinical biochemistry findings:
no effects observed
Urinalysis findings:
no effects observed
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:
no effects observed
Histopathological findings: neoplastic:
no effects observed
Details on results:
CLINICAL SIGNS AND MORTALITY: Overall survival was excellent for the 2 year study with mortality never exceeding 58 % for any treatment group. For males, a slight increase in mortality was observed following 700 days exposure to 3000 ppm PGME vs. controls. At study termination, the cumulative mortality in males was 40, 32, 40 and 58 % for the control, 300, 1000, 3000 ppm groups respectively. For females no treatment related increase in mortality was observed. At study termination, the cumulative mortality in females was 22, 30, 28 and 16 % for the control, 300, 1000, 3000 ppm groups respectively.
At 3000 ppm PGME the sedative effects, characterized by decreased activity and incoordination, were observed in both sexes during the first week of exposures. The animals generally recovered within hours following the six hour exposure periods. During the second week of exposures, the animals appeared to have accommodated to the test material as no further observation of sedative effects thought the first year exposures were noted. Other clinical observations were in general consistent with age related changes commonly observed in chronic studies with Fischer 344 rats and not due to PGME exposures. A number of rats in each group had external masses or nodules in various locations of the skin, subcutaneous tissues and in preputial or clitoral glands areas. These masses/nodules were distributed across all groups without regard to treatment.

BODY WEIGHT AND WEIGHT GAIN: For male rats, there were numerous instances of treatment groups having a statistically significant difference in body weights or weight gain vs controls. These differences included decreases as well as increases and did not display a dose response relationship. For females, occasional statistically identified differences from controls were also observed but lacked dose response during the 13 weeks of study. However, by 118 days treatment, the mean body weights females exposed to 3000 ppm PGME were consistently and statistically lower than control values by approximately 3-7 %. This effect on the body weights of female rats was considered to be treatment related.

OPHTHALMOSCOPIC EXAMINATION: There were no ophthalmologic abnormalities noted in any of the group A study animals that were considered to be treatment related.


HAEMATOLOGY: There were no hematological effects in male and female rats that were attributable to PGME exposures. Occasional statistical significant differences were observed that lacked dose response, were not reproducible (between the 6, 12, 18 and 24 month sampling intervals) or differed in a manner in which that was not toxicologically relevant. The only statistically identified hematological change was an increase in total leukocyte counts in 300 ppm PGME males at 6 months which was not considered treatment related as it represented an increase and not a decrease in counts, was not observed at other time points, and lacked any histopathological correlate. No effects were observed in WBC differential counts. The only statistically identified changes included, elevated leukocyte counts in females exposed to 300 and 1000 ppm PGME for 6 months, but not at 3000 ppm PGME or at later time periods, increased erythrocyte and platelet counts in females exposed to 3000 ppm PGME after 6 months but not at later times periods and slight decrease in platelet counts in females exposed to 3000 ppm PGME for 12 months but not at 18 or 24 months. These changes were all considered to be a reflection of normal biological variability. As with the males, no treatment related effects were observed in WBC differential counts and blood cell morphology.


CLINICAL CHEMISTRY: Occasional findings of statistically significant but not treatment related included, elevated BUN in rats exposed to 1000 ppm for 6 months, elevated cholesterol in rats exposed to 1000 and 3000 ppm for 6 months, elevated triglycerides levels in rats exposed to 300 and 1000 ppm for 6 months or 3000 ppm for 24 months, increased creatinine levels in rats exposed to 3000 ppm at 6, 12 and 24 months, decreased creatinine phosphokinase activity in rats exposed to 1000 ppm only for 24 months. In addition, the mean calcium level in male rats exposed to 1000 ppm for 6 months was statistically identified as elevated and the phosphorous level of rats exposed to 3000 ppm for 18 months was identified as decreased relative to controls. All of those statistically identified differences were considered to be a result of normal variability and unrelated to PGME exposure since they were not either reproducible, lacked a dose response relationship or lacked histopathological correlate. Elevated serum alkaline phosphatase activities were also observed in male rats exposed to 3000 ppm PGME for 6, 12 and 24 months or to 1000 ppm for 24 months. This enzyme is typically associated with degenerative changes or obstruction of the biliary duct system, which was morphologically unaffected by PGME exposure. Changes observed in electrolytes were statistically identified but not treatment related and lacked a dose response relationship.


URINALYSIS: The slight changes in urinalysis parameters that were observed in two weeks i.e. increased urine pH in male rats exposed to 3000 ppm PGME but these changes were not apparent in this study following 6, 12, 18, and 24 months of exposure. There were no treatment related effects evident in urinalysis including microscopic examinations of urine micro sediment from male and female rats.


ORGAN WEIGHTS: A statistically significant increase in liver weights (18.6 % absolute and 21.2 % relative to body weight) was observed in high exposure group males, relative to controls at the terminal 24 month sacrifice, similar increases were present at earlier time points. For female rats, there were no significant liver weight differences observed in the high concentration group at the terminal sacrifice, however there were statistically significant liver weight increases at earlier time points. Kidney weights were elevated in males exposed to 3000 ppm PGME following 6, 12, 18 and 24 months of exposure. At 24 months, this increase averaged 22 % for absolute kidney weights and 28 % for kidney weights relative to their body weights. Although statistically identified at all time periods were slight <5 % absolute and did not correlate to any histopathological changes in renal tissues. No other changes in organ weights interpreted to be treatment related were observed in male or female rats.


GROSS PATHOLOGY: A slight increase in the incidence of dark foci in the livers of male rats exposed to 1000 and 3000 ppm PGME for 2 years was correlated with the presence of altered hepatocellular foci observed histologically .All other gross pathological observations and the occurrence of palpable mass were distributed across all groups, including controls and were typical for rats of this age and strain.


HISTOPATHOLOGY: The major toxicological effects of exposure were observed in the liver and kidneys. Effects of lesser importance were observed in nasal tissues and lungs. The clinical pathology data did not indicate significant treatment related hepatotoxicity. The lack of dose response in the incidence of tumors in males does not suggest a treatment related effect.

Effect levels

Dose descriptor:
NOEL
Effect level:
300 ppm
Sex:
male/female
Basis for effect level:
other: overall effects

Target system / organ toxicity

Critical effects observed:
not specified

Applicant's summary and conclusion

Conclusions:
In conclusion, PGME did not cause a dose related increase in tumors in male and female rats exposed to 0, 300, 1000 and 3000 ppm PGME vapors for 6 hours/day, 5 days/week for up to 2 years. A NOEL of 300 ppm PGME was established for this study.
Executive summary:

Groups of 50 male and 50 female Fischer 344 per sex per concentration were whole body exposed to targeted vapor concentrations of 0, 300, 1000 and 3000 ppm PGME (colorless liquid) under dynamic airflow conditions 6 hours/day, 5 days/week for up to 2 years.

Rats were received frombreeding Laboratories,. Mice were kept for acclimatization for 1 week period. At study initiation rats were of approximately 6 -7 weeks old. Rats were housed 2/sex/cage in stainless steel cages with wire bottoms. A standard laboratory diet (Purina Certified Laboratory Chow, Ralston Purina Co.) supplied to rats adlibitum except during exposure. Adlibitum water was supplied to rats except during exposure.

 

Monitored for effects included clinical observations, body weights, hematology, clinical chemistry, urinalysis, opthalmoscopy, necropsy, organ weights, gross pathology and histopathology.

Overall survival was excellent for the 2 year study with mortality never exceeding 58 % for any treatment group. For males, a slight increase in mortality was observed following 700 days exposure to 3000 ppm PGME vs. controls. At study termination, the cumulative mortality in males was 40, 32, 40 and 58 % for the control, 300, 1000, 3000 ppm groups respectively. For females no treatment related increase in mortality was observed. At study termination, the cumulative mortality in females was 22, 30, 28 and 16 % for the control, 300, 1000, 3000 ppm groups respectively. At 3000 ppm PGME the sedative effects, characterized by decreased activity and incoordination, were observed in both sexes during the first week of exposures. The animals generally recovered within hours following the six hour exposure periods. During the second week of exposures, the animals appeared to have accommodated to the test material as no further observation of sedative effects thought the first year exposures were noted. Other clinical observations were in general consistent with age related changes commonly observed in chronic studies with Fischer 344 rats and not due to PGME exposures. A number of rats in each group had external masses or nodules in various locations of the skin, subcutaneous tissues and in preputial or clitoral glands areas. These masses/nodules were distributed across all groups without regard to treatment.

For male rats, there were numerous instances of treatment groups having a statistically significant difference in body weights or weight gain vs controls. These differences included decreases as well as increases and did not display a dose response relationship. For females, occasional statistically identified differences from controls were also observed but lacked dose response during the 13 weeks of study. However, by 118 days treatment, the mean body weights females exposed to 3000 ppm PGME were consistently and statistically lower than control values by approximately 3-7 %. This effect on the body weights of female rats was considered to be treatment related.

There were no ophthalmologic abnormalities noted in any of the group A study animals that were considered to be treatment related.

There were no hematological effects in male and female rats that were attributable to PGME exposures. Occasional statistical significant differences were observed that lacked dose response, were not reproducible (between the 6, 12, 18 and 24 month sampling intervals) or differed in a manner in which that was not toxicologically relevant. The only statistically identified hematological change was an increase in total leukocyte counts in 300 ppm PGME males at 6 months which was not considered treatment related as it represented an increase and not a decrease in counts, was not observed at other time points, and lacked any histopathological correlate. No effects were observed in WBC differential counts. The only statistically identified changes included, elevated leukocyte counts in females exposed to 300 and 1000 ppm PGME for 6 months, but not at 3000 ppm PGME or at later time periods, increased erythrocyte and platelet counts in females exposed to 3000 ppm PGME after 6 months but not at later times periods and slight decrease in platelet counts in females exposed to 3000 ppm PGME for 12 months but not at 18 or 24 months. These changes were all considered to be a reflection of normal biological variability. As with the males, no treatment related effects were observed in WBC differential counts and blood cell morphology.

Occasional findings of statistically significant but not treatment related included, elevated BUN in rats exposed to 1000 ppm for 6 months, elevated cholesterol in rats exposed to 1000 and 3000 ppm for 6 months, elevated triglycerides levels in rats exposed to 300 and 1000 ppm for 6 months or 3000 ppm for 24 months, increased creatinine levels in rats exposed to 3000 ppm at 6, 12 and 24 months, decreased creatinine phosphokinase activity in rats exposed to 1000 ppm only for 24 months. In addition, the mean calcium level in male rats exposed to 1000 ppm for 6 months was statistically identified as elevated and the phosphorous level of rats exposed to 3000 ppm for 18 months was identified as decreased relative to controls. All of those statistically identified differences were considered to be a result of normal variability and unrelated to PGME exposure since they were not either reproducible, lacked a dose response relationship or lacked histopathological correlate. Elevated serum alkaline phosphatase activities were also observed in male rats exposed to 3000 ppm PGME for 6, 12 and 24 months or to 1000 ppm for 24 months. This enzyme is typically associated with degenerative changes or obstruction of the biliary duct system, which was morphologically unaffected by PGME exposure. Changes observed in electrolytes were statistically identified but not treatment related and lacked a dose response relationship.

The slight changes in urinalysis parameters that were observed in two weeks i.e. increased urine pH in male rats exposed to 3000 ppm PGME but these changes were not apparent in this study following 6, 12, 18, and 24 months of exposure. There were no treatment related effects evident in urinalysis including microscopic examinations of urine micro sediment from male and female rats.

There were no changes observed in organ weights related to PGME exposure.There were no gross pathological findings attributable to PGME exposure in male and female rats. The gross lesions observed were generally distributed across all groups or occurred sporadically and were typical for rats of this age and strain.

There were no histopathological findings attributable to PGME exposure in male and female rats. The histopathological lesions observed were generally distributed across all groups or occurred sporadically and were typical for rats of this age and strain. The major toxicological effects of exposure were observed in the liver and kidneys. Effects of lesser importance were observed in nasal tissues and lungs. The clinical pathology data did not indicate significant treatment related hepatotoxicity. The lack of dose response in the incidence of tumors in males does not suggest a treatment related effect.

 In conclusion, PGME did not cause a dose related increase in tumors in male and female rats exposed to 0, 300, 1000 and 3000 ppm PGME vapors for 6 hours/day, 5 days/week for up to 2 years. A NOEL of 300 ppm PGME was established for this study.