Registration Dossier

Administrative data

Endpoint:
chronic toxicity: oral
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
no data
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
The study does not fulfill all requirements of a 1 or 2 years repeated dose toxicity study. Limited parameters included (e.g. on clinical biochemistry, microscopy on distinct organs only) and results were not described in details. The study nevertheless is still useful for the assessment purposes although does not follow the current requirements.

Data source

Reference
Reference Type:
publication
Title:
Comparative toxicity of synthetic and natural glycerin.
Author:
Hine C. et al.
Year:
1953
Bibliographic source:
Arch. Ind. Hyg. Occup. Med. 7: 282-291

Materials and methods

Test guideline
Qualifier:
no guideline followed
Guideline:
other: not applicable
Deviations:
not applicable
Principles of method if other than guideline:
not applicable
GLP compliance:
not specified
Limit test:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
Synthetic glycerol was a commercial product manufactured by Shell Chemical Corporation. Purity 99.5%. The impurities contained mostly water, and there was no spectroscopic evidence of benzene or naphtalene nuclei or any other aromatic compounds. The only specific contaminants have been glycerin polymers and glyceraldehyde.

Natural glycerin was selected at random from market stock.

Each specimen was analysed acc. to the "Pharmacopoeia of the US" and chloride values were determined. There were minor differences between the natural and synthetic glycerin - the residue on ignition, the content of fatty acids and esters was grater for natural glycerin.

Test animals

Species:
rat
Strain:
Long-Evans
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: inbred stock of the Institute of Experiemntal Biology, Univeristy of California, Berkley
- Age at study initiation: no data
- Weight at study initiation: mean 101.4 g for males; 100.7 g for females
- Fasting period before study: not applicable
- Housing: individual numbered cage in a bank cages, 8 units high and 22 units long.
- Diet (e.g. ad libitum): The diet consisted of a standard dog-food meal with which the glycerin was thoroughly mixed. The fed was prepared once a week and stored in stoneware crocks. The use of metabolic jars with mesh tops for feeding permitted free access to food.
- Water: free access
- Acclimation period: no data

No data on housing conditions available.
ENVIRONMENTAL CONDITIONS: no data

Administration / exposure

Route of administration:
oral: feed
Vehicle:
unchanged (no vehicle)
Details on oral exposure:
The fed was prepared once daily. The metabolic jars were refilled weekly and the unconsumed feed was discarded.
Analytical verification of doses or concentrations:
not specified
Details on analytical verification of doses or concentrations:
no data
Duration of treatment / exposure:
2 years for the low and middle dose group; 1 year for the high dose group
Frequency of treatment:
daily, free access to food.
Doses / concentrations
Remarks:
Doses / Concentrations:
5, 10, 20% of natural or synthetic glycerin
Basis:
nominal in diet
No. of animals per sex per dose:
22 animals/sex per treatment; 26 controls
Control animals:
yes, plain diet
Details on study design:
- Doses: 5, 10, 20% of natural or synthetic glycerin in diet, calculated to be equivalent to doses of: males 2000, 4000, 8000 mg/kg b.w. ; females: 2500, 5000, 10000 mg/kg b.w. These doses are given based on the average value per group (based on food consumption).

- Dose selection rationale: The treatment levels were chosen because the side products, which average less than 0.2% of the synthetic glycerin, would be ingested in significant amounts, while the highest level of glycerin fed, 20%, was not likely to disturb metabolism.

- Rationale for animal assignment (if not random): random
Positive control:
not required

Examinations

Observations and examinations performed and frequency:
The animals were checked daily; at weekly intervals removed from cages and inspected. Health and activity was noted and weight recorded. The mean percent weight gain for each group was calculated at approx. four-week intervals.

At 3, 6, 12, 18 and 24 months after the start of the experiment, five rats from each group were placed in separate metabolism cages for from 24 to 48 hours and urine specimens were collected. Blood was withdrawn from the tail veins for hematologic studies.
Hematology: erythrocyte and leukocyte count and haemoglobin.
Urinanalysis: albumin, glucose, casts and red and white blood cells
Sacrifice and pathology:
At the end of one year, all rats on the 20% diets were decapitated and ensanguined. The glycogen content of the livers was determined. The livers were analysed for total lipid content. Organ/body weight ratios were determined both on these animals and on those which survived untilthe termination of the experimental period of 105 weeks. The livers, kidneys, hearts, spleens and lungs were removed, blottered on filter paper and weighted.
Necropsies were preformed on all animals. Any gross abnormalities were noted. Sections of liver, spleen, adrenal gland, kidney, small intestine, bladder, reproductive organs were prepared for microscopic studies.
Other examinations:
no data
Statistics:
Statistical differences between the ratios of organ weight to body weight were determined for the different dosage levels.

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:
no effects observed
Water consumption and compound intake (if drinking water study):
not specified
Ophthalmological findings:
not specified
Haematological findings:
no effects observed
Description (incidence and severity):
limited number of parameters examined.
Clinical biochemistry findings:
no effects observed
Description (incidence and severity):
limited number of parameters examined.
Urinalysis findings:
no effects observed
Description (incidence and severity):
limited number of parameters examined
Behaviour (functional findings):
not specified
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Gross pathological findings:
no effects observed
Histopathological findings: non-neoplastic:
no effects observed
Histopathological findings: neoplastic:
no effects observed
Details on results:
The authors concluded that examination of the growth curves and statistical analysis of mean values at 13, 52 and 105 weeks did not show any statistical difference between the groups of males and the groups of females. However, this seems to be an inverse dose relation between body weight gain and dose groups.

Hemoglobin determination and urinalyses were carried out at 3, 6, 12, 18, 24 months (after 18 and 24 months only low and middle dose groups) without demonstrating any differences between blood and urine of the experimental groups and of the controls.
There was no evidence of depression of hemoglobin in any group.

There was a high incidence of albuminuria, ranging from 30 % in females on 5% natural glycerin to 92% on females on 20% natural glycerin. The incidence of males and females in the control group was 64% and 53% respectively. Albuminuria in the groups receiving synthetic glycerin ranged from 47% in females on 5% synthetic glycerin to 74% in males on 5% synthetic glycerin. The degree of glycosuria ranged from 0 in males and females on 20% synthetic glycerin to 56% in male controls. Due to the wide variation on degree of albuminuria and glycosuria and to their random distribution throughout the experimental groups, no significance could be attached to these findings.

No significant differences were demonstrated between natural and synthetic glycerin by the results of the specific biochemical analysis of liver glycogen and lipid.

The mean organ/body weight ratios were statistically significantly different in 12/180 comparisons. In two groups (5% and 10%) the organs of animals fed synthetic glycerin were heavier than the controls of fed natural glycerin.

Females receiving 20% synthetic glycerin had liver/body weight ratios statistically significantly higher than the controls (10% increase). Females receiving 5% synthetic glycerin had heart/body weight ratio significantly greater than the ones on 5% natural glycerin.

The authors stated that from comparison of these data there was concluded that there was no evidence of stress due to ingestion of either glycerin, as would have been initiated by increased organ/body weight ratios.

Pathology: there were no lesions attributed to either natural or synthetic glycerin or to theoretical contaminants.
The variety of spontaneous diseases was present in 68 rats (out of 157). The lowest incidence was in the groups fed 20% natural or synthetic glycerin and those fed 5% synthetic glycerin.
Only inflammatory diseases occurred in 27 rats.
Tumor presence was assessed after 1 year in the highest dose group and after 2 years in the low and middle dose group. In total 28 rats had tumors; in one rat there were two bening lesions. Several rats had only neoplasms but also not related inflammatory lesions.
Malignant neoplasms occurred in 16 rats. There were 5 each in the groups on 10% natural glycerin and on 10% synthetic glycerin as well as 5 in the control group. Beside, one rat from the 5% natural glycerin had malignant tumor.
Benign tumors were present in 12 rats. Nine of them occurred in the synthetic glycerin groups and there were none in the controls.
No information was available on survival and time of occurrence of tumors.

Effect levels

Dose descriptor:
NOAEL
Effect level:
10 000 mg/kg bw/day (nominal)
Sex:
male/female
Basis for effect level:
other: overall effects based on the absence of treatment related effects in high dose animals.

Target system / organ toxicity

Critical effects observed:
not specified

Any other information on results incl. tables

no data

Applicant's summary and conclusion

Conclusions:
The chronic toxicity study (2-years 5 or 10% of natural or synthetic glycerin in diet; 1 year for 20 % natural or synthetic glycerin in diet) was carried out with males and females of Long-Evans rats. Based on the reported absence of treatment related effects in high dose animals, NOAEL was calculated as 10000 mg/kg bw.

In absence of details on survival, time of occurrence of tumors and nature of tumors, based on this study no conclusion can be drawn on the carcinogenic properties of glycerin.