Ethylene carbonate

Carcinogenicity

Administrative data

Endpoint:

carcinogenicity: oral

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

other: Low number of animals, several non-carcinogens and carcinogens were tested in the same room (up to 480 rats); high mortality in males of the high dose group; screening test, limited documentation.

Data source

Reference

Reference 1

Reference Type:

publication

Title:

Carcinogenicity tests of certain environmental and industrial chemicals

Author:

Weisburger EK Ulland BM, Nam J, Gart JJ, Weisburger JH

Year:

1981

Bibliographic source:

J Nat Cancer Inst 67: 75-88

Reference 2

Reference Type:

publication

Title:

Chronic Toxicity and Carcinogenicity of Industrial Chemicals and Pesticides

Author:

Ulland B, Weisburger EK, and Weisburger JH

Year:

1973

Bibliographic source:

Toxicol Appl Pharmacol 25: 446

Materials and methods

Principles of method if other than guideline:

Screening study: Carcinogenic potential of several chemicals studied in parallel experiments in long-term feeding studies in rats.

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

Ethylene carbonate

EC Number:

202-510-0

EC Name:

Ethylene carbonate

Cas Number:

96-49-1

Molecular formula:

C3H4O3

IUPAC Name:

1,3-dioxolan-2-one

Test material form:

solid: crystalline

Details on test material:

- Name of test material (as cited in study report): Ethylene carbonate
- Purity: > 99%
- Physical state: fine crystals

Test animals

Species:

rat

Strain:

other: Charles River CD

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratories, North Wilmington, Mass., USA
- Age at study initiation: appr. 5 weeks
- Weight at study initiation: no data
- Fasting period before study: no data
- Housing: 2 rats per cage
- Diet & water ad libitum
- Acclimation period: 7-10 d
- All rats in the same animal room, but the position of the cages on the racks and the rack positions within the room were changed monthly.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): no data
- Humidity (%): no data
- Air changes (per hr): air-condition, no further data
- Photoperiod (hrs dark / hrs light): no data

Administration / exposure

Route of administration:

oral: feed

Vehicle:

other: diet, Wayne Lab Blox meal

Details on exposure:

- Dose range finding studies
Acute studies: single dose given by gavage; if no effects were noted, daily doses were administered up to 14 days; weight gain, food intake, and general toxicologic effects recorded; gross necropsies on rats that died, were moribund, or were killed. The results used as a guide for doses in the following experiments. MTD for the chronic study was determined in a repeated dose toxicity study: 5 dose levels were administered via the diet to groups of 3 animals each over 30 days, followed by 30 days post exposure observation period; weight gain and clinical signs recorded; necropsy performed.
No results were documented on these dose range finding studies.

- Main study
Diet prepared twice weekly and stored in a refrigerator at 4°C until needed.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

- Stability of the test substance in the diet
Mixtures with diet were stored for 10 days at room temperature and degradation of test substance examined; diet mixture extracted with a suitable solvent (water, methanol, or acetone), and the recovery calculated after colorimetric, spectrophotometric, or gas chromatographic determination (no further specification). The recovery was 94.5 ± 2.7%; the loss of test substance within 10 days was 7.8%.

Duration of treatment / exposure:

78 weeks (18 months); at the high dose exposure was terminated in males at week 42 and continued at week 44 with 40000 ppm

Frequency of treatment:

continuously ad libitum

Post exposure period:

26 weeks; termination at week 104

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

25 000 ppm (nominal)

Remarks:

Basis: nominal in diet; approx. 1250 mg/kg bw/day

Doses / concentrations 2

Dose / conc.:

50 000 ppm (nominal)

Remarks:

basis: nominal in diet; approx. 2500 mg/kg bw/day

Doses / concentrations 3

Dose / conc.:

40 000 ppm (nominal)

Remarks:

basis: nominal in diet; approx. 2000 mg/kg bw/day; Due to an increased mortality rate at the high dose, exposure was terminated in males at week 42 and continued at week 44 with 40000 ppm

No. of animals per sex per dose:

26
controls: number of concurrent (matched) controls not clearly stated ("control groups of animals of each sex, which were selected at the same time as those groups assigned to the testing of a set of chemicals, were initiated into the chronic studies"); treated groups also compared with "pooled" controls (historical controls in further experiments of this screening study). Pooled controls: 184 animals for each sex in 10 groups (presumably appr. 18 controls per sex in the matched control).

Control animals:

yes, plain diet

Details on study design:

Dose level at the MTD and at one-half MTD for 18 months; rats observed for 6 months before termination of the study 24 months after initiation.

Positive control:

Two groups of positive control animals received N-2-Fluorenylacetamide in the diet at 80 ppm (32 rats) or 250 ppm (20 rats); the positive control gave the expected result.

Examinations

Observations and examinations performed and frequency:

All animals were examined twice daily, 7 days a week. Rats weighed weekly during the 1st month and biweekly thereafter. Food consumption determined during the initial week and the fourth week of each subsequent 4-week period.

Sacrifice and pathology:

Moribund rats killed; at the end of week 78, 5 females of the group on the higher dose killed, necropsied, and histopathology performed; these animals were used for calculation of tumor incidence but not survival rate.
All rats were necropsied and the tissues examined histopathologically (tissues fixed in 10% neutral buffered formalin, sectioned, and stained with hematoxylin and eosin). Tissues examined: cerebrum, cerebellum, pituitary gland, spinal cord plus vertebrae, lung, heart, mediastinum, thymus, thyroid gland, parathyroid gland, liver, spleen, pancreas, adrenal gland, kidney, urinary bladder, ovary, uterus or testis, accessory sex organ, esophagus, stomach, intestinal tract, and any abnormal tissue or mass.

Other examinations:

no

Statistics:

survival: "life table method"
one-tailed Fisher's exact probability test for tumor incidence (significance level of 0.05)
Bonferroni inequality
Cochran-Armitage test for linear trend

Results and discussion

Results of examinations

Clinical signs:

effects observed, treatment-related

Mortality:

mortality observed, treatment-related

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

not specified

Food efficiency:

not specified

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

not examined

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Urinalysis findings:

not examined

Behaviour (functional findings):

not specified

Organ weight findings including organ / body weight ratios:

not specified

Gross pathological findings:

not specified

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

no effects observed

Details on results:

Mortality and clinical signs
Males: Increased mortality in high-dose males ( 3 of the high-dose males survived to 52 weeks; all died by week 60) although treatment was stopped at week 42 and resumed at 40000 ppm at week 44. 20 males in the low dose group survived to 52 weeks, only 10 survived to 78 weeks.
Females: no mortality at week 52 weeks; at week 78 23/26 of the low-dose group and 20/26 of the high-dose group alive. No effects compared to controls. Females remained unaffected clinically.

Body weight
Males: male treatment groups had substantially lower mean weights than matched controls.
Females: mean weights similar to those of the control groups.

Histopathology
Severe nephrotoxicity in high-dose males, evidenced by diffuse severe chronic nephritis. Strongly birefringent crystals (probably oxalic acid) found in the convoluted tubules of the kidney, the collecting tubules, and sometimes in the renal pelvis and urinary bladder. Low-dose males were not affected appreciably until the 60th week.

Under the conditions of this study the treated groups did not show any increase in the incidence of tumors over that of the controls. The difference in toxicity and survival between males and females may relate to differences in metabolism as a function of sex, similar to that of the hydrolysis product ethylene glycol.

Relevance of carcinogenic effects / potential:

No carcinogenic potential detected but limited validity

Effect levels

1

Dose descriptor:

LOAEL

Effect level:

25 000 ppm (nominal)

Based on:

not specified

Sex:

male

Basis for effect level:

other: nephrotoxicity

2

Dose descriptor:

NOAEL

Effect level:

50 000 ppm (nominal)

Based on:

not specified

Sex:

female

Basis for effect level:

other: toxicity

3

Dose descriptor:

NOAEL

Effect level:

50 000 ppm (nominal)

Based on:

not specified

Sex:

female

Basis for effect level:

other: carcinogenicity

Any other information on results incl. tables

No further details are presented in the result section.

Applicant's summary and conclusion

Conclusions:

In a long-term feeding study in rats no carcinogenic effects were detected, however, the experimental design was insufficient for evaluation of this endpoint.

Executive summary:

This carcinogenicity study is not valid [low number of animals, several non-carcinogens and carcinogens were tested in the same room (up to 480 rats); high mortality in males of the high dose group; screening test, limited documentation].

Male and female CD rats were exposed via the diet to 0, 25000 or 50000 ppm (corresponding to appr. 0, 1250, 2500 mg/kg bw/day) for 78 weeks (n=26 per dose per sex; presumably n=18 in controls). The study was terminated after a 26 weeks post exposure observation period at week 104. Due to an increased mortality rate at the high dose, exposure was terminated in males at week 42 and continued at week 44 with 40000 ppm. In males even the low dose resulted in reduced survival and decreased body weight; dose dependent nephrotoxic effects were detected. No effects were found in females. Under the conditions of this study the treated groups did not show any increase in the incidence of tumours over that of the controls. The difference in toxicity and survival between males and females may be related to differences in metabolism.

Data on nephrotoxicity in this study do support cross read of the results of ethylene glycol.

Conclusion: In a long-term feeding study in rats no carcinogenic effects were detected, however, the experimental design was insufficient for evaluation of this endpoint.