Diphenyl ether

Repeated dose toxicity: inhalation

Administrative data

Endpoint:

short-term repeated dose toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

1974

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: This study was conducted prior to GLP and test guidelines, but sufficient data is available for interpretation of results.

Cross-reference

Cross-reference 1

Reason / purpose for cross-reference:

reference to same study

Cross-reference 2

Reason / purpose for cross-reference:

reference to other study

Data source

Reference

Reference 1

Reference Type:

study report

Title:

Unnamed

Year:

1974

Report date:

1974

Reference 2

Reference Type:

publication

Title:

Unnamed

Year:

1974

Materials and methods

Test guideline

Qualifier:

no guideline available

Principles of method if other than guideline:

Repeated inhalation studies using rats, rabbits, and dogs were conducted at mean exposure concentrations of 0, 4.9 and 10.0 ppm DPO vapor. Exposures were 7 hours per day, 5 days per week for a total of 20 exposures. An additional group of rats w ere exposed to 0 or 20 ppm DPO vapor for atotal of 20 exposures.

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

Diphenyl ether

EC Number:

202-981-2

EC Name:

Diphenyl ether

Cas Number:

101-84-8

Molecular formula:

C12H10O

IUPAC Name:

phenoxybenzene

Details on test material:

Pure DPO

Test animals

Species:

other: Rat, rabbit, dog

Strain:

other: Sprague-Dawley rats, New Zealand albino rabbits and beagle dogs

Sex:

male/female

Details on test animals or test system and environmental conditions:

rats- female (control and 20 ppm, only) and males
rabbits- males only
dogs- males only

Food and water were not available to control or exposed animals during the daily exposures. Between exposures, food and water were provided ad libitum to all animals.

Administration / exposure

Route of administration:

inhalation: vapour

Type of inhalation exposure:

whole body

Vehicle:

other: unchanged (no vehicle)

Remarks on MMAD:

MMAD / GSD: No data

Details on inhalation exposure:

Exposures to 5 or 10 ppm DPO vapor were conducted under dynamic conditions in two one cubic meter glass-walled exposure chambers. DPO vapor was generated by metering the liquid at a controlled rate into a temperature regulated vaporization flask. Nitrogen was used to sweep the vapor from the vaporization flask into the air inlet where mixing and dilution with filtered room air occurred. The ratio of nitrogen flow to total chamber airflow was 0.005, so that the oxygen level in the chamber atmosphere was not significantly reduced. The nominal concentration of the vapor was calculated from the ratio of the rate of compound dissemination to the rate of total chamber airflow (the volume of nitrogen ejected from the generator plus the volume of make-up air ) .

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The analytical concentration of DPO vapor in the chamber was determined by gas chromatography of samples of the chamber atmosphere collected with a gas syringe. All gas chromatography was done on a 5' long by 1/8" diameter column containing a 2% SE-54 liquid phase on 80-100 mesh Chromsorb W packing. The Aerograph Model 550 chromatograph was operated isothermally at 200°C with a 225°C injection port temperature. A flame ionization detector was employed using helium as the carrier gas. A 10 ppm DPO vapor standard was used in calculating the analytical chamber
concentration. This standard was generated by vaporizing the appropriate amount of DPO into a saran bag containing 100 L of air. A solution of 10 ppm DPO in carbon disulfide gave results comparable to the gaseous standard and was therefore used as the working standard for routine chamber analysis. Both the 5 and 10 ppm nominal concentration exposure chambers were analyzed several times during each daily exposure. Exposures of rats to 20 ppm DPO vapor were conducted as previously described except a 160L glass walled chamber and filtered room air, rather than nitrogen, to sweep the vaporization flask, were used. Only the nominal concentration was determined for the 20 ppm exposures.

Duration of treatment / exposure:

7 hrs/day, 5 days/week for a total of 20 exposures in 31 or 3 days

Frequency of treatment:

5 days/week

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
Males: controls, 5 or 10 ppm (rats, rabbits and dogs)
Basis:
nominal conc.

Doses / concentrations 2

Remarks:

Doses / Concentrations:
Males and females: control and 20 ppm (rats only)
Basis:
nominal conc.

Doses / concentrations 3

Remarks:

Doses / Concentrations:
4.9 +/- 1.5 ppm and 10.0 +/- 2.0 ppm; 20 ppm (nominal only)
Basis:
analytical conc.

No. of animals per sex per dose:

Rats: 20 male rats (control, 5 or 10 ppm) and 10/sex (control and 20 ppm)
Rabbits: 4 male rabbits (control, 5 or 10 ppm)
Dogs: 2 male dogs (control, 5 or 10 ppm)

Control animals:

yes, concurrent no treatment

Details on study design:

Exposure Regimen:
Two groups of animals, each consisting of 20 male Sprague-Dawley rats of Spartan strain, 4 male New Zealand albino rabbits, and 2 male beagle dogs, were exposed, to nominal concentrations of 5 or 10 ppm DPO vapor for 7 hours per day, 5 days per week for a total of 20 exposures in 31 or 33 days, respectively. A third group of animals were kept under ambient conditions and served as controls. An additional group of 10 male and 10 female Sprague-Dawley rats of Spartan strain were exposed to a nominal concentration of 20 ppm DPO vapor for 7 hours per day, 5 days per week for a total of 20 exposures in 27 days. Equal numbers of male and female rats were kept under ambient conditions and served as controls. Food and water were not available to control or exposed animals during the daily exposures. Between exposures, food and water were provided ad libitum to all animals.

Evaluation of Toxicity
All animals were observed for signs of toxicity and irritation periodically throughout the experiment and in particular during each exposure. Body weights of all animals were recorded at regular intervals. At the termination of the study, basic hematological determinations, including red, white, and differential cell counts, hemaglobin concent rations, and hematocrit, were conducted on samples of blood from 10 rats and all of the rabbits and dogs. Also determined were blood urea nitrogen (BUN), and the activities of serum glutamic pyruvic transaminase (SGPT), and alkaline phosphatase
(AP). Additional hematological determinations were made on all rats exposed to 20 ppm DPO vapor after 1, 4, and 19 days of exposure. All animals were deprived of food, sacrificed and subjected to gross pathological examination within 20 hours after termination of the exposures. Organ weights for brain, heart, liver, kidney, and testes were obtained for all animals exposed to 0, 5 or 10 ppm DPO vapor and from 10 rats (5 per sex)
exposed to 0 or 20 ppm DPO vapor. In addition, spleen and thymus weights were obtained from 10 rats (5 per sex) exposed to 0 or 20 ppm DPO vapor, and adrenal gland weights were obtained for all dogs. All major organs and tissues, including the nasal turbinates and adjacent bone, pituitary gland, brain, trachea, thyroid, parathyroid, aorta, lungs, thoracic lymph nodes, thymus, salivary glands, liver, pancreas, small intestine, stomach, large intestine, mesenteric lymph node, adrenal gland, accessory sex glands, testes, epididymis, peripheral nerve, skeletal muscle, esophagus, urinary bladder, spleen, and any other grossly visible pathologic lesion were prepared and examined histologically. All tissues were routinely embedded in paraffin, sectioned, and stained with hematoxylin and eosin. The nasal turbinates and adjacent bone were decalcified prior to processing. Tissues were
fixed in a 10% buffered formalin fixative. The lungs of all rats and rabbits were distended with 10% buffered formalin fixative following removal. Organ to body weight ratios, as well as hematological and biochemical parameters were analyzed statistically using analysis of variance and Dunnett's test . The level of significance in all cases was p<0.05.

Positive control:

None

Examinations

Observations and examinations performed and frequency:

All animals were observed for signs of toxicity and irritation periodically throughout the experiment and in particular during each exposure. Body weights of all animals were recorded at regular intervals.

Additional hematological determinations were made on all rats exposed to 20 ppm DPO vapor after 1, 4, 19 or 20 days of exposure.

Sacrifice and pathology:

At the termination of the study, basic hematological determinations, including red, white, and differential cell counts, hemaglobin concent rations, and hematocrit, were conducted on samples of blood from 10 rats and all of the rabbits and dogs. Also determined were blood urea nitrogen (BUN), and the activities of serum glutamic pyruvic transaminase (SGPT), and alkaline phosphatase (AP).

All animals were deprived of food, sacrificed and subjected to gross pathological examination within 20 hours after termination of the exposures. Organ weights for brain, heart, liver, kidney, and testes were obtained for all animals exposed to 0, 5 or 10 ppm DPO vapor and from 10 rats (5 per sex) exposed to 0 or 20 ppm DPO vapor. In addition, spleen and thymus weights were obtained from 10 rats (5 per sex) exposed to 0 or 20 ppm DPO vapor, and adrenal gland weights were obtained for all dogs. All major organs and tissues, including the nasal turbinates and adjacent bone, pituitary gland, brain, trachea, thyroid, parathyroid, aorta, lungs, thoracic lymph nodes, thymus, salivary glands, liver, pancreas, small intestine, stomach, large intestine, mesenteric lymph node, adrenal gland, accessory sex glands, testes, epididymis, peripheral nerve, skeletal muscle, esophagus, urinary bladder, spleen, and any other grossly visible pathologic lesion were prepared and examined histologically.

Other examinations:

None

Statistics:

Organ to body weight ratios, as well as hematological and biochemical parameters were analyzed statistically using analysis of variance and Dunnett's test. The level of significance in all cases was p<0.05.

Results and discussion

Results of examinations

Clinical signs:

effects observed, treatment-related

Mortality:

mortality observed, treatment-related

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

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:

no effects observed

Histopathological findings: neoplastic:

no effects observed

Details on results:

Chamber Analysis and Observations During Exposure:
The means and standard deviations of the concentrations of DPO vapor in the two exposure chambers, as determined by analysis during the experiment, were 4.9+/-1 .5 and 10.0+/-2 .0 ppm, respectively. No signs of toxicity or irritation were observed in animals exposed to 4.9 ppm DPO vapor. Rats and rabbits exposed to 10.0 ppm exhibited mild eye and nasal irritation. Dogs exposed to 10.0 ppm exhibited no signs of toxicity or irritation. Both male and female rats exposed to 20 ppm exhibited eye and nasal irritation.

Analysis of Body Weights and Organ Weights
The body weight gains of animals exposed to either 4.9, 10.0 or 20 ppm DPO vapor were comparable to and not statistically different than those of the controls. Analysis of the data indicate statistically significant decreases in the mean absolute organ weight and the organ to body weight ratio for livers of rats exposed to both 4.9 and 10.0, but not 20 ppm-DPO vapor. A statistically significant increase in the brain to body weight ratio was observed in male rats exposed to 20 ppm.

Clinical Chemistry and Pathology
Rats exposed to 4.9 or 10.0 ppm DPO vapor exhibited a statistically significant decrease in the mean white blood cell count. Additionally, there was a statistically significant decrease in the concentration of hemoglobin in the blood of rats exposed to 10.0 ppm. Male rats exposed to 20 ppm DPO vapor exhibited a statistically significant increase in the mean white blood cell count after 19, but not 1, 4, or 20 days of exposure. Female rats exposed to this concentration exhibited statistically significant decreases in the mean white and red blood cell counts, hematocrit, and hemoglobin concent
ration after 4, but not 1, 19, or 20 days of exposure. No statistically significant differences were noted in the hematological parameters of exposed rabbits or dogs, when compared to controls.

Rabbits exposed to 4.9 and 10.0 ppm DPO vapor, as well as dogs exposed to 4.9 ppm, exhibited statistically significant decreases in BUN values. A concurrent decrease in terminal BUN values was not observed in dogs exposed to 10.0 ppm or in rats exposed to 4.9 or 10.0 ppm.

Gross and histopathological examination of all exposed and control animals revealed no discernible lesions related to exposure to 4.9, 10.0, or 20 ppm DPO vapor. Several exposed and control animals exhibited focal reddened areas in the lungs or mild lesions resulting from an occasional parasite. These findings were not considered related to the exposures to DPO vapor, as they were present in control as well as exposed animals.

Effect levels

1

Dose descriptor:

NOEL

Effect level:

4.9 ppm

Sex:

male

Basis for effect level:

other: NOEL for rats and rabbits based on eye and nasal irritation observed at higher concentrations.

2

Dose descriptor:

NOEL

Effect level:

10 ppm

Sex:

male

Basis for effect level:

other: NOEL for dogs (highest concentration tested)

Target system / organ toxicity

Critical effects observed:

not specified

Any other information on results incl. tables

DISCUSSION

Exposure of rats or rabbits to 10.0 ppm or rats to 20 ppm DPO vapor induced primary irritation of the eyes and nares. Hematological changes, including statistically significant decreases in white blood cell counts of rats exposed to 4.9 and 10.0 ppm, and decreases in the hemoglobin concentrations of rats exposed to 10.0 ppm were not observed in rabbits or dogs exposed to these concentrations. Furthermore, exposure of both male and female rats to the higher concentration of 20 ppm produced no consistent reductions in white blood cell counts or hemoglobin concentrations in either sex. For example, in the male control rats used in this investigation, a considerable variation in the mean white blood cell counts was observed. At the inception of the exposures to 20 ppm DPO vapor, the mean control white blood cell count was 20.4 +/-3.2 e3/mm3. Eighteen days later, a 14.7 +/-1.6 e3 / mm3 white blood cell count was observed for these same control rats. This, as well as all other mean hematological parameters are within the normal range of variation observed in this laboratory. Hence, the statistically significant decreases in both the white blood cell counts or hemoglobin concentrations are very likely unrelated to exposure to DPO vapor.

The statistically significant decrease in the liver to body weight ratios observed in rats exposed to either 4.9 or 10.0 ppm DPO vapor are very likely unrelated to the exposures, as there were no differences in the liver to body weight ratios of rats exposed to 20 ppm. Additionally, the liver to body weight ratios of rats exposed to 4.9 or 10.0 ppm were within the normal range of variation when compared to control rats used in previous studies in this laboratory. Further, there were no gross pathological or histopathological lesions in the organs, including liver, of any animals exposed to DPO vapor. The statistically significant increase in the brain to body weight ratios observed in rats exposed to 20 ppm DPO vapor are very likely unrelated to the exposures, because the brain to body weight ratios for the control rats are lower than normally observed in this laboratory. Additionally, the statistically significant decrease in the terminal body weight of rats exposed to 20 ppm DPO vapor was not observed during the exposures, but resulted from the food deprivation prior to sacrifice and is thus very likely unrelated to the exposures.

The statistically significant decrease in mean terminal BUN values for all exposed rabbits, as well as dogs exposed to 4.9 ppm DPO vapor likewise appear to be unrelated to exposure. The mean terminal BUN values are within the normal range of variation observed in this laboratory. For example, the mean BUN of a group of 59 control male albino rabbits was found to be 21.4 mg/%, range 15.0 - 27.0. (Unpublished data - Dow Chemical Co.) In this investigation mean terminal BUN values were 21.3, 15.0, and 16.5 mg/% for rabbits exposed to 0.0, 4.9, and 10.0 ppm DPO vapor, respectively. The decrease in terminal BUN observed in dogs exposed to 4.9 ppm is of doubtful significance, as a concurrent decrease was not observed in dogs exposed to the higher concentration of 10.0 ppm.

The results of this investigation indicate a lack of untoward effects in rats, rabbits and dogs repeatedly exposed to 4.9 ppm DPO vapor. Concentrations of 10.0 ppm DPO vapor appear to be physically irritating to rats and rabbits, but not dogs. Exposure to 20 ppm DPO vapor resulted in physical irritation as well as slight, but not statistically significant, decreases in the rate of body weight gain by male rats and concomitant changes in organ to body weight ratios, as well. Thus, the only untoward effect in animals exposed to 10.0 or 20 ppm DPO vapor for 20 days is physical irritation. Irritation, especially to the eyes and nares, would very likely precede any organic damage caused by exposure to DPO vapor. Therefore, it is suggested that occasional short term exposure of humans to 5 ppm DPO vapor should be without untoward effect. Further studies are necessary to establish the effect of chronic exposure to DPO vapor.

Applicant's summary and conclusion

Conclusions:

The results of the study indicate a lack of untoward effects in rats, rabbits and dogs repeatedly exposed to 4.9 ppm diphenyl oxide (DPO) vapor. Only untoward effect in animals exposed to 10 or 20 ppm for 20 days was physical irritation.

Executive summary:

Repeated inhalation studies using rats, rabbits, and dogs were conducted at mean exposure concentrations of 0, 4.9 and 10.0 ppm DPO vapor. Exposures were 7 hours per day, 5 days per week for a total of 20 exposures. An additional group of rats were exposed to 0 or 20 ppm DPO vapor for a total of 20 exposures. No untoward effects were observed in animals exposed to 4.9 ppm. Eye and nasal irritation were observed in rats and rabbits exposed to 10.0 ppm and in rats exposed to 20 ppm. Aside from this irritation no other untoward effects were discerned.