1,4-dioxane

Repeated dose toxicity: inhalation

Administrative data

Endpoint:

chronic toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Cross-reference

Reason / purpose for cross-reference:

reference to same study

Reference

Endpoint:

carcinogenicity: inhalation

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Reason / purpose for cross-reference:

reference to same study

Qualifier:

no guideline followed

Principles of method if other than guideline:

Method: A lifetime 2-year study with rats, with a treated and a control group

GLP compliance:

no

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Dow
- Housing: in groups of 4 or 8 during and between exposure
- Diet: ad libitum
- Water: ad libitum

ENVIRONMENTAL CONDITIONS
No data

Route of administration:

inhalation

Type of inhalation exposure (if applicable):

whole body

Vehicle:

unchanged (no vehicle)

Details on exposure:

Seven-hour daily exposures were given 5 days/week under dynamic exposure conditions in five 3.7 m3 stainless-steel vault-type chambers. A constant air flow of 373 liters/min nitrogen was maintained by means of rotary pump connetcted to the exhaust side of each chamber. The airflow was monitored with calibrated flow meters. The vapour was generated by metering liquid dioxane into an evaporation flaks heated to 100 dergees C.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

(on-line) infrared analysis

Duration of treatment / exposure:

2 years

Frequency of treatment:

7 hours/day, 5 days/week

Post exposure period:

none

Dose / conc.:

0.4 mg/L air (analytical)

Remarks:

SD = 0.018 mg/L (5 ppm); corresponding to 111 ppm

No. of animals per sex per dose:

treatment group: 288 male and 288 female animals
control group: 192 male and 192 female animals

Control animals:

yes, concurrent vehicle

Details on study design:

Since the threshold limit value for dioxane at the time of this study was started and up until 1971 was set by the American Conference of Governmental Industrial Hygienists (1971) at 0.36 mg/L (100 ppm v/v), this concentration was selected for the 2-year study.
Selection of this concentration was also supported by previous studies in our laboratory, in which groups of 24 male and 24 female rats, 3 male and 3 female rabbits, and 2 female dogs received 130-136 7-hr exposures in 180-195 days to 50 ppm dioxane vapour in air. In addition, 7 male and 8 female guinea pigs received 82 exposures in 1 1.8 days to 50 ppm dioxane vapor in air, and groups of 12 rats and 2 rabbits of each sex received. 133-136 7-hr exposures to 100 ppm. There were no adverse effects when the exposed groups were compared to control groups on the basis of appearance, demeanor, growth, mortality, hematological and clinical chemical studies, organ weights, or gross and microscopic pathological examination.

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes

DETAILED CLINICAL OBSERVATIONS: Yes: signs of toxicity including alternations in activity, demeanor, eye and nasal irritation, skin condition, respiratory distress, and tumour formation.
- Time schedule: not excatly indicated; throughout the exposure period.

BODY WEIGHT: Yes
- Time schedule for examinations: weekly

FOOD CONSUMPTION:
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: No data

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: No data

WATER CONSUMPTION: No data

OPHTHALMOSCOPIC EXAMINATION: No data

HAEMATOLOGY: Yes
- Time schedule for collection of blood: after 16 or 23 months of exposure
- Anaesthetic used for blood collection: No data
- Animals fasted: yes
- How many animals: after 16 months: 232 control rats and 340 exposed rats
after 23 months:115 control rats and 185 exposed rats
Parameters checked : PCV, RBC, Hb, WBC, WBC different; Neut, Lymph, Mono, Eosin, Baso

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: at termination of the study (after 2 years on all surviving rats)
- Animals fasted: Yes
- How many animals:103 control, 151 exposed rats
- Parameters checked: BUN, SGPT, AP and total protein

URINALYSIS: No data

NEUROBEHAVIOURAL EXAMINATION: No data

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
on succumbed and moribund rats, whenever possible moribund rats were killed for for gross examination and tissues were saved for microscopic
examination, with special attention to abnormal growths. Following gross examination body weights of liver, spleen and kidneys were recorded.

HISTOPATHOLOGY: Yes:
lungs, trachea, thoracic lymph nodes, heart, liver, pancreas, stomach, intestine, spleen, thyroid, mesentric lumph nodes, kidneys, urinary bladder, pituary, adrenals, tetstes, ovaries, oviduct, uterus, mammary gland, lacrimals gland, lymph nodes, brain, vagina, bone marrow, and any
abnormal growths.

Statistics:

Control and experimental groups were compared statistically using:
Student's T-test (heamatology, clinical chemistry),
Fisher exact probability test (morphological classification of tumours),
Yates corrected Chi-Square test (survival)

Clinical signs:

no effects observed

Dermal irritation (if dermal study):

not examined

Mortality:

no mortality observed

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

not specified

Food efficiency:

not specified

Water consumption and compound intake (if drinking water study):

not specified

Ophthalmological findings:

not specified

Haematological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

not specified

Behaviour (functional findings):

not specified

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

no effects observed

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

no effects observed

Histopathological findings: neoplastic:

no effects observed

Other effects:

not specified

Details on results:

No effects were seen on clinical signs (including activity, demeanour, eye and nasal irritation, skin condition and respiratory distress), body weights or mortality.

Some slight changes were observed in haematological values, but these were within the normal physiological limits and not considered of toxicological importance.

BUN and AP values in treated male rats were slightly decreased.

Changes in liver, kidney or spleen weights were not observed.

Upon gross and microscopic examination, no treatment-related non-neoplastic effects were found in tissues/organs, including the reproductive organs. Regarding neoplastic effects, no 1,4-dioxane characteristic nasal and liver tumours, as observed after oral administration, were seen. It is however not clear from the text whether or not the nasal cavity was adequately examined. The incidence of tumours observed in other organs/tissues appeared to be unrelated to exposure. The only difference from the control groups was an increase in lymphoreticular cell sarcomas in males (18% (37/206) versus 12% (18/150)) and in mammary gland adenoma in females (13% (29/217) versus 8% (11/139)), which were not statistically significant.

Key result

Dose descriptor:

NOAEC

Effect level:

> 400 mg/m³ air

Sex:

male/female

Basis for effect level:

other: no adverse effects were observed

Key result

Critical effects observed:

no

Data source

Reference

Reference Type:

publication

Title:

1,4-Dioxane. II. Results of a 2-year inhalation study in rats

Author:

Torkelson TR, Leong BKJ, Kociba RJ, Richter WA and Gehring PJ

Year:

1974

Bibliographic source:

Toxicol. Appl. Pharmacol. 30, 287-298

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

A lifetime 2-year study with rats, with a treated and a control group

GLP compliance:

no

Limit test:

yes

Test material

Test material information

Constituent 1

Reference substance name:

1,4-dioxane

EC Number:

204-661-8

EC Name:

1,4-dioxane

Cas Number:

123-91-1

Molecular formula:

C4H8O2

IUPAC Name:

1,4-dioxane

Test animals

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Dow
- Housing: in groups of 4 or 8 during and between exposure
- Diet: ad libitum
- Water: ad libitum

ENVIRONMENTAL CONDITIONS
No data

Administration / exposure

Route of administration:

inhalation: vapour

Type of inhalation exposure:

whole body

Vehicle:

other: unchanged (no vehicle)

Details on inhalation exposure:

Seven-hour daily exposures were given 5 days/week under dynamic exposure conditions in five 3.7 m3 stainless-steel vault-type chambers. A constant air flow of 373 liters/min nitrogen was maintained by means of rotary pump connetcted to the exhaust side of each chamber. The airflow was monitored with calibrated flow meters. The vapour was generated by metering liquid dioxane into an evaporation flaks heated to 100 dergees C.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

(on-line) infrared analysis

Duration of treatment / exposure:

2 years

Frequency of treatment:

7 hours/day, 5 days/week

Doses / concentrations

Dose / conc.:

0.4 mg/L air (analytical)

Remarks:

SD = 0.018 mg/L (5 ppm); corresponding to 111 ppm

No. of animals per sex per dose:

treatment group: 288 male and 288 female animals
control group: 192 male and 192 female animals

Control animals:

yes

Details on study design:

Since the threshold limit value for dioxane at the time of this study was started and up until 1971 was set by the American Conference of Governmental Industrial Hygienists (1971) at 0.36 mg/L (100 ppm v/v), this concentration was selected for the 2-year study.
Selection of this concentration was also supported by previous studies in our laboratory, in which groups of 24 male and 24 female rats, 3 male and 3 female rabbits, and 2 female dogs received 130-136 7-hr exposures in 180-195 days to 50 ppm dioxane vapour in air. In addition, 7 male and 8 female guinea pigs received 82 exposures in 1 1.8 days to 50 ppm dioxane vapor in air, and groups of 12 rats and 2 rabbits of each sex received. 133-136 7-hr exposures to 100 ppm. There were no adverse effects when the exposed groups were compared to control groups on the basis of appearance, demeanor, growth, mortality, hematological and clinical chemical studies, organ weights, or gross and microscopic pathological examination.

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes

DETAILED CLINICAL OBSERVATIONS: Yes: signs of toxicity including alternations in activity, demeanor, eye and nasal irritation, skin condition, respiratory distress, and tumour formation.
- Time schedule: not excatly indicated; throughout the exposure period.

BODY WEIGHT: Yes
- Time schedule for examinations: weekly

FOOD CONSUMPTION:
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: No data

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: No data

WATER CONSUMPTION: No data

OPHTHALMOSCOPIC EXAMINATION: No data

HAEMATOLOGY: Yes
- Time schedule for collection of blood: after 16 or 23 months of exposure
- Anaesthetic used for blood collection: No data
- Animals fasted: yes
- How many animals: after 16 months: 232 control rats and 340 exposed rats
after 23 months:115 control rats and 185 exposed rats
Parameters checked : PCV, RBC, Hb, WBC, WBC different; Neut, Lymph, Mono, Eosin, Baso

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: at termination of the study (after 2 years on all surviving rats)
- Animals fasted: Yes
- How many animals:103 control, 151 exposed rats
- Parameters checked: BUN, SGPT, AP and total protein

URINALYSIS: No data

NEUROBEHAVIOURAL EXAMINATION: No data

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
on succumbed and moribund rats, whenever possible moribund rats were killed for for gross examination and tissues were saved for microscopic examination, with special attention to abnormal growths. Following gross examination body weights of liver, spleen and kidneys were recorded.

HISTOPATHOLOGY: Yes:
lungs, trachea, thoracic lymph nodes, heart, liver, pancreas, stomach, intestine, spleen, thyroid, mesentric lumph nodes, kidneys, urinary bladder, pituary, adrenals, tetstes, ovaries, oviduct, uterus, mammary gland, lacrimals gland, lymph nodes, brain, vagina, bone marrow, and any
abnormal growths.

Statistics:

Control and experimental groups were compared statistically using:
Student's T-test (heamatology, clinical chemistry),
Fisher exact probability test (morphological classification of tumours),
Yates corrected Chi-Square test (survival)

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 specified

Food efficiency:

not specified

Water consumption and compound intake (if drinking water study):

not specified

Ophthalmological findings:

not specified

Haematological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

not specified

Behaviour (functional findings):

not specified

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

no effects observed

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

no effects observed

Histopathological findings: neoplastic:

no effects observed

Other effects:

not specified

Details on results:

No effects were seen on clinical signs (including activity, demeanour, eye and nasal irritation, skin condition and respiratory distress), body weights or mortality.

Some slight changes were observed in haematological values, but these were within the normal physiological limits and not considered of toxicological importance.

BUN and AP values in treated male rats were slightly decreased.

Changes in liver, kidney or spleen weights were not observed.

Upon gross and microscopic examination, no treatment-related non-neoplastic effects were found in tissues/organs, including the reproductive organs. Regarding neoplastic effects, no 1,4-dioxane characteristic nasal and liver tumours, as observed after oral administration, were seen. It is however not clear from the text whether or not the nasal cavity was adequately examined. The incidence of tumours observed in other organs/tissues appeared to be unrelated to exposure. The only difference from the control groups was an increase in lymphoreticular cell sarcomas in males (18% (37/206) versus 12% (18/150)) and in mammary gland adenoma in females (13% (29/217) versus 8% (11/139)), which were not statistically significant.

Effect levels

Key result

Dose descriptor:

NOAEC

Effect level:

> 400 mg/m³ air

Sex:

male/female

Basis for effect level:

other: no adverse health effects were observed

Target system / organ toxicity

Key result

Critical effects observed:

no