Cyclohexanone

Repeated dose toxicity: oral

Administrative data

Endpoint:

sub-chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1994

Report date:

1994

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 408 (Repeated Dose 90-Day Oral Toxicity Study in Rodents)

GLP compliance:

yes (incl. QA statement)

Remarks:

testing lab.

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Cyclohexanone

EC Number:

203-631-1

EC Name:

Cyclohexanone

Cas Number:

108-94-1

Molecular formula:

C6H10O

IUPAC Name:

cyclohexanone

Specific details on test material used for the study:

purity: 99.9%

Test animals

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

Only animals were used which were clinically free from any signs of disease. The rats were identified unambiguously by tattooing of the respective animal number into the ears.
During the study period the rats were housed singly. The animal cages were placed on the racks in such a way that uniform conditions (air inflow/air outflow/light) were guaranteed. The animals were housed in a fully air-conditioned room. The day/night rhythm was 12 hours. The food used was ground Kliba maintenance diet rat/mouse/hamster, 343 meal, which was available to the animals ad libitum as was drinking water.

Administration / exposure

Route of administration:

oral: drinking water

Vehicle:

water

Details on oral exposure:

The stability of the test substance in drinking water over a period of 4 days was checked analytically at the beginning of the study. To check the correctness of the concentrations of the drinking water solutions samples of each concentration were sent for analysis at the beginning and at the end of the study.
The preparations of the drinking water solutions was carried out twice a week. Weighed amounts of the test substance for the specific test group were diluted with the appropriate weighed amounts of drinking water. The mixtures were subsequently stirred with at magnetic stirrer for a least 30 minutes to reach complete solubility of the test substance in the drinking water.
The food used in the study was assayed for chemical as well as for microbiological contaminants. The drinking water is regularly assayed for chemical contaminants by the municipal authorities of Frankenthal and the Technical Services of BASF Aktiengesellschaft, as well as for the presence of microbes by a contract laboratory.

Analytical verification of doses or concentrations:

yes

Duration of treatment / exposure:

3 months

Frequency of treatment:

continuously

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

500 ppm

Remarks:

about 40 mg/kg bw

Doses / concentrations 2

Dose / conc.:

2 000 ppm

Remarks:

about 143 mg/kg bw

Doses / concentrations 3

Dose / conc.:

7 000 ppm

Remarks:

about 407 mg/kg bw

No. of animals per sex per dose:

10

Control animals:

yes, concurrent no treatment

Details on study design:

Data used for dose selection: 1. Subchronic studies of cyclohexanone, Final report from Frederick Cancer Research Center to NCI, January 10, 1979 partly published in 2 . W . Lijinsky and R.M. Kovatch (1986) Chronic Toxicity Study of Cyclohexanone in Rats and Mice. JNCI 77, pp. 941 - 949. 3. Preliminary results of a palatability test study (Project No. 12S0332/92069).

Examinations

Observations and examinations performed and frequency:

General observation of the animals was performed twice on working days and once on weekends or holidays. A comprehensive clinical examination was performed once weekly. Body weight of the animals as well as food and drinking water consumption was determined weekly. Daily weight change, foodeficiency and test substance intake were calculated from these data.

Sacrifice and pathology:

A complete necropsy including weighing of selected organs and gross pathological evaluation was performed in all animals. Histopathology of numerous organs was performed as required by the corresponding test guidelines.

Other examinations:

Ophthalmoscopy was performed in all animals prior to the begining of the treatment and in the high dose group and control group at the end of treatment period. Hematological and clinico-chemical examinations of numerous parameters as well as urinalysis were performed at the end of the treatment period.

Statistics:

The statistical evaluation and calculation of the data were carried out on the computer systems of the Department of Toxicology of BASF Aktiengesellschaft.

Results and discussion

Results of examinations

Clinical signs:

no effects observed

Description (incidence and severity):

No signs of toxicity were observed during clinical examination.
A yellowish-orange discoloration of urine in the bedding in the mid and high dosage groups is judged to be due to excretion of some metabolites of the test substance.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

A statistically significant reduction of body weights was observed in the animals of the high dosage group, which occurred earlier during the study period in male animals than in females. At the end an about 10% reduction of body weight resulted in this test group. This reduced body weight development was also demonstrated by decreased body weight change in test group 3 animals. In the female animals of test group 2 a reduction of weight change values occurred without leading to a statistically significant reduction of the absolute body weight.

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

Food consumption was not influenced in test group 1 and male test group 2 animals. It was sporadically significantly reduced in female animals of group 2 and 3, but nearly over the whole administration period in males of test group 3.
These findings were attributed to the strong odor and taste the test substance, preventing full acceptance of the treated water and the food by the animals.

Food efficiency:

no effects observed

Description (incidence and severity):

There was no clearcut influence of treatment on food efficiency.

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

effects observed, treatment-related

Description (incidence and severity):

Statistically significant decreases in water consumption occurred sporadically in test group 1, more often in test group 2 and over the whole study period in test group 3. In test group 3 the overall water consumption of males was reduced about 31% and that of females about 37%.
These findings were attributed to the strong odor and taste the test substance, preventing full acceptance of the treated water and the food by the animals.

Ophthalmological findings:

no effects observed

Description (incidence and severity):

No signs of toxicity were observed during examination of ophthalmoscopy.

Haematological findings:

effects observed, treatment-related

Description (incidence and severity):

In the hematology, the following test substance related changes were observed:
- Test group 3 (7000 ppm): Increase in platelets in the females.
- Test group 1 and 2 (500 ppm and 2000 ppm): No test substance related changes.
However, the increase in platelets in the females is considered of minor toxicological importance, because the significance of this isolated finding is not obvious.
In conclusion, the results of the hematology examinations revealed some treatment-related effects in the highest dose group only which are probably a result of slight changes in lipid metabolism or of reduced water consumption.

Clinical biochemistry findings:

effects observed, treatment-related

Description (incidence and severity):

In the clinical chemistry, the following test substance related changes were observed:
- Test group 3 (7000 ppm): Increase in total cholesterol, total protein and globulins in both sexes.
- Test group 1 and 2 (500 ppm and 2000 ppm): No test substance related changes.
The major treatment-related effect noted in the clinical pathology testing was the increase in total cholesterol in the serum of both sexes, which is probably due to a slight impairment of lipid metabolism at that high concentration of 7,000 ppm.
The increase in serum proteins seen in the high-dose animals might be related to the reduced water consumption.
In conclusion, the results of the clinical chemistry examinations revealed some treatment-related effects in the highest dose group only which are probably a result of slight changes in lipid metabolism or of reduced water consumption.

Urinalysis findings:

no effects observed

Description (incidence and severity):

The only substance related pathomorphological effect was the decreased terminal body weight in the high dosage group. All other findings were judged to be of spontaneous or incidental nature.

Effect levels

Dose descriptor:

NOAEL

Effect level:

143 mg/kg bw/day (nominal)

Sex:

male/female

Basis for effect level:

other: overall effects

Target system / organ toxicity

Critical effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

At the concentration of 7000 ppm signs of toxicity were observed. The reduction of water and food consumption at the lower concentrations is not considered to be an adverse health effect, but caused by the strong odor and taste of the test substance. Therefore, the NOAEL for this drinking water study is 2 000 ppm, corresponding to a dose of 143 mg/kg body weight.