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Toxicological information

Repeated dose toxicity: inhalation

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Administrative data

Endpoint:
short-term repeated dose toxicity: inhalation
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
supporting study
Study period:
4-15 March 1991
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: The study was not conducted according to guidelines but was conducted according to GLPs and the report contains sufficient data for interpretation of study results
Justification for type of information:
Read across is based on the category approach. Please refer to attached category document.

Data source

Referenceopen allclose all

Reference Type:
study report
Title:
Unnamed
Year:
1992
Report Date:
1992
Reference Type:
publication
Title:
Respiratory peripheral chemosensory irritation, acute and repeated exposure toxicity studies with aerosols of triethylene glycol
Author:
B Ballantyne, WM Snellings, JC Norris
Year:
2006
Bibliographic source:
J Appl Toxicol 26:387-396

Materials and methods

Test guideline
Qualifier:
no guideline available
GLP compliance:
yes
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
Three 5-gallon containers of TEG, Lot TS-2300l28, Tk-706, CAS No. 112-27-6, were received on January 30, 1991, from UCC&P, Texas City, TX. The purity of the test substance was determined by the GLP Analytical Skills Center at the UCC&P South Charleston, WV, Technical Center to be approximately 99.9%;

transparent, white liquid with a mild odor

Test animals

Species:
rat
Strain:
Sprague-Dawley
Sex:
male/female
Details on test animals and environmental conditions:
Sixty-five male and 65 female Sprague Dawley rats were received on February 10, 1991, from Harlan Sprague Dawley, Inc. (Indianapolis, IN). They were designated by the supplier to be approximately 34 days old (birth date was recorded as January 7, 1991) and to weigh 100-124 g and 75-99 g for the male and female rats, respectively, upon arrival. The females were nulliparous and non-pregnant.

Within 2 days of receipt, the animals were examined by the BRRC Clinical Veterinarian, and representative animals were subjected to a pretest health screen including full necropsy and histologic examination of selected tissues including respiratory organs and serum viral antibody analysis. Based on the results of these data, the Clinical Veterinarian indicated that the animals were in good health and suitable for use on this study.

The animals were housed individually in stainless steel, wire-mesh cages (15 cm x 22 cm x 18 cm). DACB® (Deotized Animal Cage Board; Shepherd Specialty Papers, Inc.) was placed under each cage and changed regularly. An automatic timer was set to provide fluorescent lighting for a 12-hour photoperiod starting at 5 a.m. Temperature and relative humidity were recorded continuously (Cole-Parmer Hygrothermograph® Seven-Day Continuous Recorder, Model No. 8368-00, Cole-Parmer Instrument Co., Chicago, IL). Temperature was routinely maintained at 64-79°F; relative humidity was routinely maintained at 40-70%. Any minor exceptions to these specified ranges were noted in the raw data.

Tap water (Municipal Authority of Westmoreland County, Greensburg, PA) was available ad libitum except during exposures. Water was provided by an automatic watering system with demand control valves mounted on each rack, except during the water consumption period. Water analyses were provided by the supplier, the NUS Corporation, Materials Engineering and Testing Co., and Lancaster Laboratories, Inc. at regular intervals. EPA standards for maximum levels of contaminants were not exceeded. Powdered, certified AGWAY® PROLAB® Animal Diet Rat, Mouse, Hamster 3200 (Agway Inc.) was available ad libitum except during exposures. Analyses for chemical composition and possible contaminants of each feed lot were performed by Agway Inc.

Animal Acclimation
The acclimation period was 3 weeks for the animals. During this period, the animals were weighed 3 times at scheduled intervals. Detailed clinical
observations were conducted in conjunction with body weight measurements. Cage-side animal observations were conducted at least once daily, and an additional mortality check was conducted each day (morning). The animals were examined approximately 2 weeks prior to the initiation of the study by a Clinical Veterinarian. Animals considered unacceptable for the study, based on the clinical signs, ophthalmic examination, body weights, or body weight gains, were rejected. The fate of rejected animals and the reasons for rejection were documented in the study record.

Administration / exposure

Route of administration:
inhalation: aerosol
Type of inhalation exposure:
other: report does not state type of exposure but based on chamber size must have been a whole-body exposure
Vehicle:
air
Remarks on MMAD:
MMAD / GSD: The particle size distribution was measured using a TSI Particle Aerodynamic Sizer Model APS 3300 (TSI Incorporated, St. Paul, MN). The dilution ratio was 100:1, and the sample collection time was 30 seconds for all target concentrations. These determinations were made at least 2 times per week per chamber. The data collected were analyzed by the method of Hinds (1982) to obtain the MMAD and the geometric standard deviation.

The MMAD for the 500, 2000, and 5000 mg/m3 exposures was 1.92, 2.57, and 2.94 microns, respectively, with a geometric standard deviation (Og)
of 1.56, 1.65, and 1.70, respectively.

Reference:
Hinds, W. C. (1982). Aerosol Technology: Properties, Behavior, and Measurement of Airborne Particles. John Wiley & Sons, New York, NY, 85.
Details on inhalation exposure:
Inhalation Chamber Description and Operation
The inhalation chambers (Young & Bertke, Cincinnati, OH) were constructed from stainless steel with glass windows for animal observation, were rectangular (132 x 85 x 91 cm) in shape with a pyramidal top and bottom. The volume of each chamber was approximately 1330 liters, and the airfow rate was approximately 300 liters/minute (13-14 air changes per hour). A Dwyer Magnehelic® pressure gauge (Dwyer Instruments, Inc., Michigan City, IN) was used to monitor chamber airflow. The theoretically-derived time required for each chamber to reach 99% of the target concentration (t99) was calculated to be 20 minutes. Chamber temperature and relative humidity were recorded using a Fisherbrand® dial type thermometer (Fisher Scientific, Pittsburgh, PA) and an Airguide humidity indicator (Airguide Instrument Co., Chicago, IL), respectively. Temperature and relative humidity measurements were recorded approximately 2 times each hour of exposure.

Aerosol Generation
Liquid TEG was metered from a piston pump (RPG-6-l/8" - 500 mg/m3 ; RPG-20-l/4" - 2000 mg/m3; RPG-20-3/8" - 5000 mg/m3; Fluid Metering, Inc., Oyster Bay, NY) into an atomizer (Spraying Systems Co., Wheaton, IL) fitted with a No. 1650 liquid nozzle and a No. 64 air nozzle. The atomizer was inserted into the top of the inhalation chamber turret where the liquid aerosol was dispersed throughout the chamber by filtered chamber supply air. The operating pressure of the atomizer was 20 psi.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Chamber Atmosphere Measurements
Chamber concentrations of TEG were analyzed by gravimetric methods. Six samples were obtained from the TEG aerosol exposure chambers each day. The sample flowrates were 4.25, 1.81, and 0.81 liters/minute for the 500, 2000, and 5000 mg/m3 target concentrations, respectively. The sample collection time ranged from 10 to 20 minutes. A glass fiber filter (47 mm; type A-E; Gelman Instrument Co., Ann Arbor, MI) used to collect the TEG aerosol was connected to a dry gas meter (Rockwell International, Pittsburgh, PAl, a critical orifice, and a vacuum pump (Terracon Corp., Waltham, MA). The nominal concentration was calculated by dividing the total amount of TEG used to generate the exposure atmosphere by the total volume of air delivered to each chamber.

Control animals were exposed to filtered air only. For the target concentrations of 500, 2000, and 5000 mg/m3 , mean gravimetric exposure concentrations (± SD) were determined to be 494 (± 14.2), 2011 (± 94.4) and 4824 (± 182.9) mg/m3 , respectively.
Duration of treatment / exposure:
Animals were exposed for 6 hours per day for 5 consecutive days. After 2 days without exposure, the animals were exposed for an additional 4 consecutive days.
Doses / concentrationsopen allclose all
Dose / conc.:
494 mg/m³ air (analytical)
Remarks:
500 mg/m3 (targeted)
Dose / conc.:
2 011 mg/m³ air (analytical)
Remarks:
2000 mg/m3 (targeted)
Dose / conc.:
4 824 mg/m³ air (analytical)
Remarks:
5000 mg/m3 (targeted)
No. of animals per sex per dose:
15 males and 15 females in control and high dose group and 10 males and 10 females in low and intermediate dose groups. (Five animals/sex of the control and high concentration groups were assigned to a 2-week recovery group.)
Control animals:
yes, concurrent no treatment
Details on study design:
The exposures began on March 4, 1991 (Study Day 1). Animals were exposed for 6 hours per day for 5 consecutive days. After 2 days without exposure, the animals were exposed for an additional 4 consecutive days. The 6-hour exposure period for each exposure day was defined as the time when the aerosol generation system was turned on and subsequently turned off. All surviving animals were sacrificed on March 15, 1991, after a total of 9 exposures.

Note The 6-hour exposure period for each exposure day was defined as the time when the aerosol generation system was turned on and subsequently turned off.
Positive control:
No data

Examinations

Observations and examinations performed and frequency:
In-Life Evaluations
All animals were individually observed for signs of toxic effects except during the exposures. During the exposures, observations were recorded on a group basis. Preceding and following each exposure, observations were recorded for animals exhibiting overt clinical signs. At the time of body weight measurements and just preceding sacrifice, detailed observations were performed on all animals. On nonexposure days, the animals were observed once a day for overt clinical signs and twice a day for mortality.

Body weight data were collected for all animals on the morning prior to initiation of the first exposure (denoted as Day 1 of the study), preceding the second, fifth, sixth, and seventh exposures, and immediately preceding sacrifice.

Food and water consumption measurements were obtained over an approximate 15-hour period following the eighth exposure of male rats and the ninth exposure of female rats (excluding the animals designated for the 2-week recovery period). All animals were housed individually in Nalgene® metabolic cages with stainless steel, wire-mesh bottoms, approximately 20 cm diameter x 11 cm high (Nalge Company, Rochester, NY) during the measurement period.

Prior to the first exposure, the eyes of all rats were examined by a Veterinary Ophthalmologist using indirect ophthalmoscopy following dilation of the pupils with MYDRIACYL® 1% (tropicamide 1.0%) Ophthalmic Solution. Following the ninth exposure, the eyes of all surviving rats (excluding the animals designated for the 2-week recovery period) were again examined by a Veterinary Ophthalmologist by the procedure previously mentioned.
Sacrifice and pathology:
Clinical Pathology Evaluation
Prior to sacrifice, blood was collected from all rats (excluding animals designated for the 2-week recovery period) for hematology and clinical chemistry determinations. Blood was obtained from the orbital sinuses of methoxyflurane-anesthetized animals. Food was removed from the animal cages prior to the start of the blood collection period, but water was supplied ad libitum.

Following the eighth exposure of male rats and following the ninth exposure of female rats, urine was collected from all surviving rats (excluding animals designated for the 2-week recovery period) while the rats were in the metabolism cages (see Food and Water Consumption). Food and water were available ad libitum. Two or three thymol crystals were added as a preservative to the collection tubes.

The following parameters were measured or calculated:
Hematology
hematocrit
hemoglobin
erythrocyte count
mean corpuscular volume (MCV)
mean corpuscular hemoglobin (MCH)
mean corpuscular hemoglobin concentration (MCHC)
total leukocyte count
differential leukocyte count
platelet count
reticulocyte count

Clinical Chemistry
glucose
urea nitrogen
creatinine
total protein
albumin
globulin (calculated)
total bilirubin
direct bilirubin
indirect bilirubin
calcium
phosphorus
sodium
potassium
chloride
aspartate aminotransferase (AST)
alanine aminotransferase (ALT)
creatine kinase (CK) with isoenzymes
lactate dehydrogenase (LDH) with isoenzymes
gamma-glutamyl transferase (GGT)
sorbitol dehydrogenase (SDH)
alkaline phosphatase (ALK)

Urinalysis and Urine Chemistry
osmolality
pH
protein
glucose
ketones
bilirubin
blood
urobilinogen
total volume
color and appearance
microscopic elements
N-acetyl-b-D-glucosaminidase (NAG)

The blood smears for the differential leukocyte counts and reticulocyte counts were prepared for all groups, but were evaluated only for the control and highest exposure concentration group that survived the exposure regimen.

Anatomic Pathology Evaluations
At the end of exposures, all rats (except animals designated for the 2-week recovery period) were anesthetized with methoxyflurane and euthanized by exsanguination via the brachial blood vessels. A complete necropsy was performed on all animals (except animals designated for the 2-week recovery period). The liver, spleen, brain, lungs, kidneys, adrenals, and testes (males) were weighed for all sacrificed animals. The following tissues were collected and saved in 10% neutral buffered formalin:

gross lesions*
lungs*
nasal turbinates (four sections)*
brain
thymus
trachea*
heart*
larynx*
liver*
spleen
kidneys*
adrenals*
testes
ovaries
lymph node
(submandibular)
eyes
bladder*
spinal cord*
sciatic nerve*
tibial nerve*

Tissues with an asterisk for 10 rats per sex from the control group and 2000 mg/m3 exposure concentration group and from all rats (15 per sex) from the 5000 mg/m3 exposure concentration group were processed histologically and examined microscopically. In addition, the respiratory tract (nasal cavities, trachea, larynx, and lungs) was also examined from the 500 mg/m3 exposure concentration group rats.

Other examinations:
No additional information available.
Statistics:
The data for continuous, parametric variables were intercompared for the exposure and control groups by Levene's test for homogeneity of variances, by analysis of variance, and by t-tests. The t-test was used, if the analysis of variance was significant, to delineate which groups differed from the control group. If Levene's test indicated homogeneous variances, the groups were compared by an analysis of variance for equal variances followed, when appropriate, by pooled variance t-tests. If Levene's test indicated heterogeneous variances, the groups were compared by an analysis of variance for unequal variance followed, when appropriate, by separate variance t-tests. Frequency data were compared using Fisher's exact tests. All statistical tests, except the frequency comparisons, were performed using BMDP Statistical Software (Dixon, 1990). The frequency data tests are described in Biometry (Sokal and Rohlf, 1981). The probability value of p < 0.05 (two-tailed) was used as the critical level of significance for all tests.

References:
Dixon, W. J. (1990). BMDP Statistical Software, University of California Press, Berkeley, CA.

Sokal, R. R. and Rohlf, F. J. (1981). Biometry, W. H. Freeman and Company, San Francisco, CA

Results and discussion

Results of examinations

Clinical signs:
effects observed, treatment-related
Description (incidence and severity):
All rats from the high dose group died before the scheduled necropsy.
Mortality:
mortality observed, treatment-related
Description (incidence):
All rats from the high dose group died before the scheduled necropsy (between days 2 & 5)
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
Males - 2000 and 5000 mg/m3. Females - 5000 mg/m3.
Food consumption and compound intake (if feeding study):
effects observed, treatment-related
Description (incidence and severity):
Females - Increased at 500 and 2000 mg/m3.
Food efficiency:
not specified
Water consumption and compound intake (if drinking water study):
effects observed, treatment-related
Description (incidence and severity):
Males - Increased at 2000 mg/m3. Females - Increased at 500 and 2000 mg/m3.
Ophthalmological findings:
no effects observed
Haematological findings:
effects observed, treatment-related
Description (incidence and severity):
Female - Increased RBC in 2000 mg/m3 group.
Clinical biochemistry findings:
effects observed, treatment-related
Description (incidence and severity):
Male - increase ALT activity/decrease in serum creatinine in 2000 mg/m3 group. Female increases in BUN, ALT, ALK, and inorganic phosphorus and decreases in glucose, creatinine, and chloride in 2000 mg/m3 group.
Urinalysis findings:
effects observed, treatment-related
Description (incidence and severity):
Male - Increased urine volume and decreased urine osmolality and pH at 2000 mg/m3. Female - Increased urine volume and decreased pH.
Behaviour (functional findings):
not specified
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Description (incidence and severity):
liver and kidney weights
Gross pathological findings:
effects observed, treatment-related
Description (incidence and severity):
Unkempt fur, swollen eyelids with periocular and perinasal discharge and crusting, and multifocal or diffuse color change due to congestion and/or hemorrhage of various organs and tissues.
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Description (incidence and severity):
Females - alveolar histiocytosis at 2000 mg/m3.
Histopathological findings: neoplastic:
not specified
Details on results:
All references of differences in group mean values in the following text refer to comparisons between the exposure group and the control group, unless otherwise noted. Repeated reference to the control will not be made in order to simplify the text.

Clinical Observations and Mortality
All rats in the 5000 mg/m3 exposure group died or were sacrificed in a moribund condition on or before the end of exposure day 5. Exposure-related clinical observations included ataxia, prostration, unkempt fur, labored respiration (males only), ocular discharge, swollen periocular tissue, perinasal and periocular encrustation, and blepharospasm in both sexes from the 5000 mg/m3 exposure concentration group. The only significant signs of toxicity in rats from the 500 and 2000 mg/m3 exposure concentration groups were periocular swelling and perinasal encrustation.

Body Weights
Statistically significant decreases in body weights were seen in male rats exposed to 2000 and 5000 mg/m3 of TEG aerosol. Significant decreases in body weight gains were also seen in male rats exposed to 5000 mg/m3 TEG. Female rats also showed statistically significant decreases in body weights and body weight gains, but only in the 5000 mg/m3 exposure concentration group.

Food and Water Consumption
Since the highest exposure concentration of TEG (5000 mg/m3 ) killed all the rats before the end of exposures, food and water consumption measurements were obtained only on the remaining exposures group of animals and controls. Statistically significant increases in food consumption were noted for females from the 500 and 2000 mg/m3 exposure concentration groups, but not in any of the male rats exposed to TEG. Water consumption was significantly increased in females exposed to 500 and 2000 mg/m3 TEG and in male rats exposed to 2000 mg/m3 TEG.

Ophthalmic Examinations
No ophthalmic lesions that could be attributed to the TEG aerosol exposure were noted in rats that survived the exposure regimen.

Clinical Pathology Evaluations
Since all the animals in the 5000 mg/m3 exposure concentration group died before the end of the exposures, blood samples were only collected from the two remaining exposure groups and control rats. Male rats did not show statistically significant changes in the hematology parameters measured. Female rats in the 2000 mg/m3 exposure group had a significant increase in total erythrocyte counts with a significant decrease in MCV.

Since all the animals in the 5000 mg/m3 exposure concentration group died before the end of the exposures, blood samples were only collected from the two remaining exposure groups and control rats. The only statistically significant changes in male rats were an increase in ALT activity and a decrease in serum creatinine in the 2000 mg/m3 exposure concentration group. Female rats from the 2000 mg/m3 exposure concentration group showed statistically significant increases in urea nitrogen, ALT, ALK, and inorganic phosphorus and decreases in glucose, creatinine, and chloride. Females from the 500 mg/m3 exposure concentration group had significant increases in ALK activity, inorganic phosphorus, and total protein.

Since all the animals in the 5000 mg/m3 exposure concentration group died before the end of the exposures, urine samples were only collected from the 2 remaining exposure groups and control rats. Male rats from the 2000 mg/m3 exposure concentration group had statistically significant increases in total urine volume and significant decreases in urine osmolality, pH, and NAG activity. However, the decreased NAG activity was probably due to dilution of the enzyme because of the increased urine volume, since the total NAG enzyme excreted was actually slightly elevated in both male and female rats from the 2000 mg/m3 exposure concentration group. Female rats from the 2000 mg/m3 exposure concentration group had statistically significant increases in total urine volume, and decreases in pH.

Organ Weights, Necropsy Observations, and Microscopic Diagnoses
The only statistically significant changes observed for male rats were increases in liver and kidney weights relative to body weights in the 2000 mg/m3 or the 500 and 2000 mg/m3 exposure concentration groups, respectively. Statistically significant changes in female rats included increases in absolute weights and in weights relative to body and brain weights for liver and kidneys from animals in the 2000 mg/m3 exposure concentration group. Female rats exposed to 2000 mg/m3 TEG also showed a significant increase in adrenal gland weight relative to brain weight.

The most notable gross findings from TEG-exposed rats for both those sacrificed and those which died during the study were unkempt fur, swollen
eyelids with periocular and perinasal discharge and crusting, and multifocal or diffuse color change due to congestion and/or hemorrhage of various organs and tissues. Hyperinflation of the lungs (failure of lungs to collapse when chest cavity was opened) was observed in 5 males and 10 females from the 5000 mg/m3 exposure concentration group. Ocular opacities were also seen in 5 males and 5 females from this latter exposure group.

The most prominent microscopic lesions found in the 5000 mg/m3 TEG-exposed rats which died or were sacrificed moribund involved congestion and, occasionally, hemorrhage of the pituitary, nasal cavities, brain, and lungs of both sexes. Congestion of the kidneys and hemorrhage of the thymus were also relatively common in the females.

The only significant microscopic lesion seen was in female rats sacrificed after the 2000 mg/m3 exposure regimen and was limited to minimal to mild
alveolar histiocytosis. Similar findings were seen in both sexes of rats exposed to 500 mg/m3 TEG, but these latter findings were not significant.

Effect levels

Dose descriptor:
LOEC
Effect level:
494 mg/m³ air (analytical)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: Minimal liver effects noted (slight increase in liver enzyme levels).

Target system / organ toxicity

Critical effects observed:
not specified

Any other information on results incl. tables

Among exposure groups, the daily mean chamber temperature and relative humidity ranged from 20.5-24.2°C and 39.9-54.9%, respectively.

Table 1 TRIE'l'HYLENE GLYCOL: NINE-DAY AEROSOL INHALATION STUDY SUMMARY OF URINALYSIS

            Group, mg/m3
 Parameter  0  500  2000  5000
 Day 11 Males        
 Total volume mean (ml)  7.6 (1.97)  9.1 (1.79)  17.1 (6.21)**  N.D.
 Osmolality (mOsm/kg)  2153 (341.9)  2047 (331.4)  1771 (279.2)*  N.D.
 pH  6.9 (0.39)  6.8 (0.24)  6.2 (0.26)**  N.D.
 Day 12 Females        
 Total Volume (mL)  8.0 (4.29)  9.9 (2.64)  16.8 (5.54)**  N.D.
 Osmolality (mOsm/kg)  1894 (612.5)  1695 (320.1)  1696 (296.9)  N.D.
 pH  7.2 (0.88)  6.9 (0.21)  6.2 (0.26)**  N.D.

N=10

N.D. = No Data, all animals died before scheduld sacrifice.

* Significantly different from control group (p < .05)

** Significantly different from control group (p < .01)

TABLE 2

TRIETHYLENE GLYCOL: NINE-DAY AEROSOL INHALATION STUDY IN RATS

SUMMARY OF ABSOLUTE AND RELATIVE ORGAN WEIGHTS (GRAMS)

ANIMALS SACRIFICED AT DAY 12

                        Group, mg/m3
      Control     500     2000     5000
 Parameter  Absolute  Relative  Absolute  Relative  Absolute  Relative  Absolute  Relative
 Males                
 Final Body Weight  297.5 (13.69) ---   302.1 (15.18) ---   286.6 (16.77) ---   N.D.  N.D.
 Liver  12.220 (0.9011)  4.107 (0.2460)  12.938 (1.0778)  4.281 (0.2490)  13.159 (1.3653)  4.585 (0.2921)**  N.D.  N.D.
 Kidney  2.301 (0.1610)  0.773 (0.0451)  2.216 (0.1430)  0.733 (0.0293)*  2.344 (0.2226)  0.817 (0.0516)*  N.D.  N.D.
 Females                
 Final Body Weight  201.3 (10.85)  ---  201.1 (9.32) ---   204.5 (18.55) ---   N.D.  N.D.
 Liver  6.886 (0.5243)  3.418 (0.1303)  7.107 (0.5225)  3.534 (0.1852)  7.869 (1.0877)*  3.836 (0.2401)**  N.D.  N.D.
 Kidney  1.512 (0.0789)  0.751 (0.0195)  1.501 (0.0954)  0.747 (0.0360)  1.639 (0.1079)**  0.804 (0.0399)**  N.D.  N.D.

N=10

N.D. = No Data, all animals died before scheduld sacrifice.

* Significantly different from control group (p < .05)

** Significantly different from control group (p < .01)

Applicant's summary and conclusion

Conclusions:
Inhalation exposures to 5000 mg/m3 of TEG aerosol for 6 hours/day produced 100% mortality within 5 days. At lower exposure concentrations over the course of 9 daily exposures, gross evidence of toxicity included periocular and perinasal irritation in both sexes exposed to 2000 mg/m3 and in males at 500 mg/m3. The only statistically significant microscopic finding was a minimal to mild increase in alveolar histiocytosis in female rats exposed to 2000 mg/m3 TEG aerosol. Biochemical findings suggest that the liver may be a target organ for toxicity by repeated inhalation exposure to a high concentration of a respirable aerosol of TEG. Minimal effects (irritation and increased serum ALK activity) were seen at 500 mg/m3 , the lowest exposure concentration tested in this study. Preening of the fur at these high aerosol concentration exposures might hav eled to a confounding factor from the resultant oral intake.
Executive summary:

Four groups, each consisting of 10 Sprague Dawley® rats per sex, were exposed to an aerosol of triethylene glycol (TEG) (CAS No. 112-27-6) at target concentrations of 0 (control), 500, 2000 and 5000 mg/m3 for 6 hours per day for 9 exposures during a 2-week period. An additional 5 animals per sex were added to the high exposure concentration and control groups for planned postexposure recovery observations. Control animals were exposed to filtered air only. For the target concentrations of 500, 2000, and 5000 mg/m3, mean analytical exposure concentrations (± SD) were determined to be 494 (± 14.2), 2011 (± 94.4) and 4824 (± 182.9) mg/m3, respectively. A mean mass median aerodynamic diameter (MMAD) for all 3 exposure groups was 2.48 microns with a mean geometric standard deviation (og) of 1.6. Determinants of toxic effects were clinical observations, ophthalmic examinations, body and organ weights, hematologic and serum clinical chemistry evaluations, urinalysis, and macroscopic and microscopic evaluations.

For all TEG-exposed rats, exposure-related clinical observations occurred. At 4824 mg/m3, clinical observations included ataxia, prostration, unkempt fur, labored respiration (males only), ocular discharge, swollen periocular tissue, perinasal and periocular encrustation, and blepharospasm in both sexes unless noted otherwise. At 494 and 2011 mg/m3, there were swollen periocular tissues and perinasal encrustations. Statistically significant decreases in body weights and body weight gains were also seen in animals exposed to 4824 mg/m3 of TEG. At 2011 mg/m3, there were statistically significant decreases in body weights in males from Exposure Day 5. Females from the 2011 mg/m3 exposure concentration group and rats of both sexes from the 494 mg/m3 exposure concentration group had body weights and body weight gains that were not significantly different from the controls. The most notable gross findings from TEG-exposed rats were unkempt fur, swollen eyelids with periocular and perinasal discharge and crusting, and multifocal or diffuse color change due to congestion and/or hemorrhage of various organs and tissues.

Rats from the 5000 mg/m3 exposure concentration group all died or were sacrificed in a moribund condition on or before the beginning of Exposure Day 5. Therefore, only limited data were obtained from these animals. In addition to the gross pathology findings noted above, hyperinflation of the lungs (failure of lungs to collapse when the chest cavity was opened) was observed during necropsy in 5 males and 10 females from the 5000 mg/m3 exposure concentration group. Ocular opacities were also seen in 5 males and 5 females from this exposure group. The most prominent microscopic lesions found in the 5000 mg/m3 TEG-exposed rats which died or were sacrificed moribund involved congestion and, occasionally, hemorrhage of many organs and tissues. The pituitary, nasal mucosa, brain, and lungs were affected in many of the rats of both sexes. Congestion of the kidneys and hemorrhage of the thymus were also relatively common in the females.

For TEG-exposed rats that survived the exposure regimen, food consumption was statistically significantly increased in an exposure concentration-related fashion for females only at 494 and 2011 mg/m3. Water consumption was statistically significantly increased in both sexes at 2011 mg/m3 and in females at 494 mg/m3. The only statistically significant hematological effects were seen in females from the 2011 mg/m3 group, and included slight increases in erythrocyte count, and slight decreases in mean corpuscular volume. Notable clinical chemistry findings were increased activities of alanine aminotransferase at 2011 mg/m3 and alkaline phosphatase at 494 and 2011 mg/m3 , and slight increases in blood urea nitrogen and inorganic phosphorous in females from the 494 and 2011 mg/m3 exposure concentration groups. Urinalysis showed statistically significant increases in urine volume and decreased osmolality, pH, and N-acetyl-S-D-glucosaminidase activity at 2011 mg/m3 , with a trend for changes in these values at 494 mg/m3. Absolute liver and kidney weights were increased in females from the 2011 mg/m3 exposure concentration, group and increased relative (to body weight) weights were measured for both organs at 2011 mg/m3. There was no histological evidence of liver or kidney injury noted in animals from any exposure concentration group. The only microscopic lesion seen was minimal to mild alveolar histiocytosis, which was in excess of that for the controls at 2011 mg/m3 , but not at 494 mg/m3. The above findings indicate impairment of liver function, but without morphological evidence of organ injury.

This study shows that daily inhalation exposures to TEG aerosol at or above concentrations of 5000 mg/m3 were fatally toxic to rats within 5 days. Similar exposures for up to 9 days at or below concentrations of 2000 mg/m3, however, did not result in life threatening signs of toxic effects. The urinary changes and associated increase in water consumption are consistent with an osmotic diuresis resulting from the excretion of absorbed TEG and its metabolites. There were no consistent findings suggestive of renal injury. The increased serum enzyme activities suggest minimal hepatotoxicity, which, for this study, has a threshold exposure concentration for this toxic response that is near to 494 mg/m3.

A NOEC could not be established. Preening of the fur at these high aerosol concentration exposures might hav eled to a confounding factor from the resultant oral intake.