Vinyltoluene

Carcinogenicity

Administrative data

Endpoint:

carcinogenicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1980 - 1982

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

other: limited investigations, no actual results presented, only tabulated statistical analysis

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1987

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 453 (Combined Chronic Toxicity / Carcinogenicity Studies)

Deviations:

yes

Remarks:

limited investigations, no actual results presented, only tabulated statistical analysis

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

4-methylstyrene

EC Number:

210-762-8

EC Name:

4-methylstyrene

Cas Number:

622-97-9

Molecular formula:

C9H10

IUPAC Name:

1-methyl-4-vinylbenzene

Test animals

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

Rats were bred at the institute and were approximately 6 weeks old when assigned to the study. Housed in groups of 10 initially, after 15 weeks of treatment males were housed in groups of 5. Tap water (glass bottles) and diet (pelleted product no 710050204 prepared by Mangimificio Corticella, Bologna, Italy) were available ad libitum, except during exposure period. Temperature was maintained between 22 °C + 3 °C and relative humidity 40-60 %. Fluorescent lighting was on a 12 hours/day cycle.

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

olive oil

Remarks:

Oleificion Venturi, Spoleto, Italy

Details on exposure:

Administered with a glass syringe and stainless steel needle tipped with a stainless steel ball.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Standard deviations form thoretical were less than 10 % of the target concetrations.

Duration of treatment / exposure:

once daily/ 5 days/ week

Frequency of treatment:

104 weeks

Post exposure period:

none

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

10 mg/kg bw/day (actual dose received)

Doses / concentrations 2

Dose / conc.:

50 mg/kg bw/day (actual dose received)

Doses / concentrations 3

Dose / conc.:

250 mg/kg bw/day (actual dose received)

Doses / concentrations 4

Dose / conc.:

500 mg/kg bw/day (actual dose received)

No. of animals per sex per dose:

Carcinogencitiy: 60 males and 60 females for the 10, 50 and 150 mg/kg/day groups and 90 males and 90 females for the 500 mg/kg/day group
Chronic toxicity: 30 males and 30 females

Control animals:

yes, concurrent vehicle

Details on study design:

60 male and 60 female controls for the carcinogenicity study and 30 males and 30 females for the toxicity study.
Rationale for dose selection:
In a pilot study groups 3 male and 3 female Sprague Dawley rats (21 weeks old) were given the test substance in olive oil at 0, 50 and 250 mg/kg body weight once daily, 5 days/week for 3 weeks. Feed and water were freely available. Mortality was monitored daily and body weights every 3 days. After 21 days animals were scarified and limited histology conducted. In this study 250 mg/kg/day was the NOEL.
In the report it is stated that dosing in the oncogenicity study stopped after 108 weeks, but that the study was terminated at 122 weeks.

Examinations

Observations and examinations performed and frequency:

Clinical observations: morality twice daily, detailed clinical observations once weekly.
Body weight: weekly for the first 13 weeks and then every 2 weeks thereafter.
Clinical pathology: week 26 and 78 form 10 males and 10 females/group. Blood samples form the orbital sinus, urine samples overnight in metabolism cages.
Haematology samples were examined for haematocrit, haemoglobin, erythrocyte, leukocyte count and differentials.
Clinical chemistry samples were examined for serum glutamic pyruvic transaminase Serum glutamic oxaloacetic transaminase, creatinine, and alkaline phosphatase.
Urine samples were examined for appearance, pH, glucose, bilirubin, haemoglobin, specific gravity, ketones, protein, urobilinogen and volume and microscopic examination of sediment.

Sacrifice and pathology:

At termination animals were killed by exanguination under sodium pentobarbital. The weight of the brain, thymus, adrenal heart, kidney, liver, lungs, testis with epididymis, uterus, mesenteric lymph nodes and ovaries were recorded.
Tissues were fixed in 10 % neutral buffered formalin. The following tissues were examined: skin, mammary gland, zymbal glands, parotid glands, submaxillary glands, harderian glands, nasal and oral cavities, tongue, pharynx, larynx, aorta, adipose tissue, sciatic nerve, muscle, brain, pituitary, spinal cord, eyes, mandibular salivary gland, thyroid, thymus, trachea, oesophagus, lungs, heart, liver, spleen, kidneys, adrenals, stomach, pancreas, duodenum, jejunum, ileum, colon, cecum, mesenteric lymph nodes, urinary bladder, testes with epididymides, prostate, ovaries, uterus, femur, bone marrow and any unusual lesions.
Histopathology was conducted on control and high dose group; in addition the following were examined for all groups: gross lesions, brain, zymbal glands, thymus, lungs, liver, spleen, pancreas, kidneys, adrenals, oesophagus, stomach, urinary bladder, prostate, uterus, ovaries, testes and epdidymus.

Statistics:

At selected interval survival rates were evaluated as a linear function of dose and the Pearson product-moment correlation coefficient was calculated.
Body weight: one-way analysis of variance and Duncan’s multiple range procedure.
Clinical pathology: homogeneity by the Bartlett test. Followed by on-way ANOVA and t-tests (homogeneous data) or Kruskal-Wallis and Mann Whitney comparison (non-parametric).
Tumor incidence: Fisher’s exact test

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):

no effects observed

Food efficiency:

not examined

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

no effects observed

Ophthalmological findings:

not examined

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:

Survival was reduced in males given 350 or 500 mg/kg/day (by up to 20 %), no similar effect was seen in females.
There were no effects on body weight or food consumption.
There were no changes in clinical pathology that were considered to be of toxicological significance.
There was histopathological evidence of systemic toxicity or of carcinogenicity. The test substance did not induce the formation of neoplasms, nor did it influence the natural rates of neoplasia in Sprague-Dawley rats.

Relevance of carcinogenic effects / potential:

No evidence of carcinogenicity.

Effect levels

1

Key result

Dose descriptor:

NOAEL

Effect level:

500 mg/kg bw/day

Based on:

test mat.

Sex:

female

2

Key result

Dose descriptor:

NOAEL

Effect level:

50 mg/kg bw/day

Based on:

test mat.

Sex:

male

Basis for effect level:

other: reduced survival at 250 mg/kg/day

Applicant's summary and conclusion

Conclusions:

Under the study conditions, survival was reduced in males given 350 or 500 mg/kg/day (by up to 20 %). No similar effect was seen in females. There were no effects on body weight or food consumption. There were no changes in clinical pathology that were considered to be of toxicological significance. There was no histopathological evidence of systemic toxicity or of carcinogenicity. The test substance did not induce the formation of neoplasms, nor did it influence the natural rates of neoplasia in Sprague-Dawley rats. The NOAEL was 50 mg/kg/day in males and 500 mg/kg/day in females

Executive summary:

A study was conducted to determine the carcinogenicity potential of the test substance. In a combined chronic and oncogenicity study, Sprague-Dawley rats were administered the test substance in olive oil at dose levels of 0, 10, 50, 250 and 500 mg/kg bw/day, 5 days/week for 108 weeks. The later dose of 500 mg/kg bw/day was administered to oncogenicity animals only. The combined total of animals in each group was 90 males and 90 females. Under the study conditions, survival was reduced in males given 250 or 500 mg/kg bw/day (by up to 20%). No similar effect was seen in females. There were no effects on body weight or food consumption. There were no changes in clinical pathology that were considered to be of toxicological significance. There was no histopathological evidence of systemic toxicity or of carcinogenicity. The test substance did not induce the formation of neoplasms, nor did it influence the natural rates of neoplasia in Sprague-Dawley rats. The NOAEL was 50 mg/kg bw/day in males (based on mortality) and 500 mg/kg bw/day in females (Maltoni, 1987).