Toluene

Repeated dose toxicity: inhalation

Administrative data

Endpoint:

chronic toxicity: inhalation

Remarks:

combined repeated dose and carcinogenicity

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Non-guideline, non-GLP, animal experimental study, published in peer reviewed literature, notable limitations in design, but contributing to weight of evidence.

Data source

Reference

Reference Type:

publication

Title:

Chronic toxicity and oncogenicity bioassay of inhaled toluene in Fischer-344 rats

Author:

Gibson JE and Hardisty JF

Year:

1983

Bibliographic source:

Fundamental and Applied Toxicology 3, 315-319

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 453 (Combined Chronic Toxicity / Carcinogenicity Studies)

Deviations:

yes

Remarks:

- only 5/sex/group examined for chronic toxicity at 1 year

GLP compliance:

not specified

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Toluene

EC Number:

203-625-9

EC Name:

Toluene

Cas Number:

108-88-3

Molecular formula:

C7H8

IUPAC Name:

toluene

Details on test material:

- Name of test material (as cited in study report): high purity toluene
- Supplier: Shell Oil Company, Oak Brook, IL, USA in two shipments. First shipment for the initial 21.5 months and the second for the final 2.5 months of exposure.
- Analytical purity: > 99.98%
- Impurities (identity and concentrations): benzene content was less than 0.01% and 0.004%, for the first and second lot respectively

Test animals

Species:

rat

Strain:

other: Fischer-344 rats [CDF(F-344)/CrIBr]

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratories, Inc., Wilmington, MA., USA
- Age at study initiation: approx. 6-7 weeks
- Housing: group housed, sexes separately, 10/cage in stainless steel suspended cages
- Diet: standard laboratory diet (Wayne Lab-Blox F6, Allied Mills Inc., Chicago, IL., USA) ad libitum (except during exposure)
- Water: ad libitum
- Acclimation period: quarantined for at least 10 days

ENVIRONMENTAL CONDITIONS: No details reported

IN-LIFE DATES: Not reported

Administration / exposure

Route of administration:

inhalation: vapour

Type of inhalation exposure:

whole body

Vehicle:

other: air

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: rectangular stainless steel and glass chambers (nominal volume 8.0 m3)
- Source and rate of air: absolute and charcoal filtered air separate from the room air supply
- Temperature, humidity, pressure in air chamber: temperature 22°C / relative humidity 50%. The inhalation chambers containing toluene were maintained at slight sub-atmospheric pressure (0.1 in - 0.5 in H2O). Control chambers were under slight positive pressure (0.1 in - 0.5 in H20).
- Air flow rate: approx. 2000 L/min
- Generation: toluene vapour was generated by bubbling clean dry air (dew point -40°C) through liquid toluene. The rate of vapour generation was regulated by controlling airflow into the generator flask.

TEST ATMOSPHERE
- Brief description of analytical method used: gas chromatography
- Samples taken from breathing zone: not reported

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The time weighted average concentration of toluene for each exposure group was 0.0, 30.1, 99.7, 299.0 ppm for target concentrations of 0, 30, 100 and 300 ppm, respectively.

Duration of treatment / exposure:

6 h/day

Frequency of treatment:

5 days/week, up to 24 months (interim kills at 6, 12 and 18 months)

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
0, 30, 100, 300 ppm
Basis:
other: target concentration

Doses / concentrations 2

Remarks:

Doses / Concentrations:
0, 30.1, 99.7, 299.0 ppm
Basis:
other: time weighted average concentration

Doses / concentrations 3

Remarks:

Doses / Concentrations:
0, 113, 377 or 1131 mg/m3
Basis:
nominal conc.

No. of animals per sex per dose:

120

Control animals:

yes, sham-exposed

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes (for dead and moribund animals)
- Time schedule: once/day non-exposure days, twice/day exposure days

DETAILED CLINICAL OBSERVATIONS: Yes (including palpation and measurement of tissue masses)
- Time schedule: every 2 weeks

BODY WEIGHT: Yes
- Time schedule for examinations: beginning of the study (week 0), weekly for the first 6 months, every other week from 6 to 24 months and immediately prior to sacrifice

FOOD CONSUMPTION: No

WATER CONSUMPTION: No

OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations: prior to sacrifice
- Dose groups that were examined: All

HAEMATOLOGY: Yes
- Time schedule for collection of blood: 6, 12, 18 and 24 months (prior to termination)
- Anaesthetic used for blood collection: no data
- Animals fasted: yes
- How many animals: selected (no further detail reported)
- Parameters examined: haemoglobin concentrations, haematocrits, total erythrocyte counts and total and differential leukocyte count. Mean corpuscular volumes, mean corpuscular haemoglobins, and mean corpuscular haemoglobin concentrations were calculated.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: 6, 12, 18 and 24 (months prior to termination)
- Animals fasted: yes
- How many animals: selected (no further detail reported)
- Parameters examined: blood urea nitrogen (BUN), serum glutamic pyruvic transaminase (SGPT) activity, and serum alkaline phosphatase (SAP) activity

URINALYSIS: Yes
- Time schedule for collection of urine: 16 hour period prior to blood collection (at 6, 12, 18 and 24 months)
- Metabolism cages used for collection of urine: yes
- Animals fasted: yes
- Parameters examined: appearance, specific gravity, protein, pH, ketones, glucose and microscopic particles

Sacrifice and pathology:

SACRIFICE AND GROSS PATHOLOGY: Animals killed at each interval, and all survivors at 24 months, were exsanguinated following carbon dioxide anaesthesia. Each was examined grossly and the brain, heart, kidneys, liver, lungs and gonads weighed.

HISTOPATHOLOGY: The following tissues were examined histopathologically: brain, spinal cord, peripheral nerve, pituitary, parathyroid, salivary gland, heart, lungs, spleen, liver, pancreas, oesophagus, adrenals, lymph nodes, kidneys, bladder, prostate, ovaries, uterus, fallopian tubes, stomach, small intestine, large intestine, skeletal muscle, thymus, skin, mammary gland, bone marrow, adipose tissue, aorta, ear canal, nasal turbinate, trachea, tibial and plantar nerves, lumbar, sacral and dorsal ganglia, proximal and distal hind limb, eyes and testes.

Statistics:

Analysis of variance (Kruskal-Wallis test for ratios): absolute body weight, total body weight change (surviving animals), organ weights, organ weight/body weight and organ weight/brain weight ratios. Other techniques for multiple comparisons: Tukey's for equal-sized groups, Scheffe's for groups of unequal sizes. Tests for homogeneity of variance, transformed (natural logarithm) as needed, and analysis of variance were used for haematology data.

Results and discussion

Results of examinations

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

no effects observed

Ophthalmological findings:

no effects observed

Haematological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

no effects observed

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:

There were 140 unscheduled deaths (14.6% of 960 animals) over the 2-year course of the study. The distribution of spontaneous deaths among the treatment groups was not significantly different from controls.

There were no differences between control and toluene exposed groups with regard to clinical observations, blood chemistry analyses, urinalysis, ophthalmology, gross or histopathological findings.

The males in the toluene treatment groups were significantly heavier than the control males throughout the study although there was no clear cut dose response relationship. A similar finding was noted for the females but the effect disappeared during the final weeks of the study. Neither observation was considered to be adverse.

Female rats exposed to 100 and 300 ppm of toluene for 24 months had slightly, but significantly, reduced haematocrits and for the 300 ppm group only the mean corpuscular haemoglobin concentration was slightly, but significantly, increased. Other haematology parameters were not significantly different from controls.

Effect levels

1

Dose descriptor:

NOAEC

Remarks:

chronic toxicity

Effect level:

300 ppm (nominal)

Sex:

male/female

Basis for effect level:

other: no toxicologically significant effects at highest dose tested (300 ppm)

2

Dose descriptor:

NOAEC

Effect level:

1 131 mg/m³ air (nominal)

Sex:

male/female

Basis for effect level:

other: no toxicologically significant effects at highest dose tested (1131 mg/m3)

Target system / organ toxicity

Critical effects observed:

not specified

Any other information on results incl. tables

All statistically significant differences from control were considered to be of no toxicological significance.

Applicant's summary and conclusion

Conclusions:

Toluene does not cause adverse effects in the rat following inhalation exposure to 300 ppm for up to 24 months. The NOAEC for chronic systemic or local toxicity in this study was 300 ppm (1131 mg/m3).

Executive summary:

Chronic toxicity of inhaled toluene was assessed in Fischer-344 rats exposed to 0, 30, 100 or 300 ppm 6 h/day, 5 days/week for 6, 12 or 18 months. There were no toxicologically significant effects on bodyweight, clinical signs, ophthalmoscopy, haematology, blood and urine clinical chemistry, organ weights or gross and microscopic pathology. The NOAEC for chronic systemic and local toxicity from this study was 300 ppm (1131 mg/m3) for an exposure duration of 18 months.