Ashes (residues), rice husk

Carcinogenicity

Administrative data

Endpoint:

carcinogenicity: oral

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

other information

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Basic data given

Data source

Reference

Reference Type:

publication

Title:

Characterization and toxicological behavior of synthetic amorphous hydrophobic silica

Author:

Lewinson, J. et al.

Year:

1994

Bibliographic source:

Regul Toxicol Pharmacol. 20(1 Pt 1):37-57

Materials and methods

Principles of method if other than guideline:

Carcinogenicity 24-months study in rats (one dose level)

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

Silane, dichlorodimethyl-, reaction products with silica

EC Number:

271-893-4

EC Name:

Silane, dichlorodimethyl-, reaction products with silica

Cas Number:

68611-44-9

IUPAC Name:

271-893-4

Details on test material:

- Name of test material (as cited in study report): Aerosil R 972 (Fumed Hydrophobic Silica, FHS)
- Analytical purity: >99.8%

Test animals

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Insitute de Medicine legale et Institute d'Hygiene Industrielle et de Medicine du Travail, Marseille, France
- Weight at study initiation: 70 g
- Housing: The animals were housed in metal cages in groups of five animals of the same sex.
- Diet (e.g. ad libitum): MAB1 (Lacassangne, France). The untreated diet was available ad libitum.

Administration / exposure

Route of administration:

oral: feed

Vehicle:

unchanged (no vehicle)

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

24 months

Frequency of treatment:

daily

Post exposure period:

no post-exposure period

Doses / concentrations

Remarks:

Doses / Concentrations:
100 mg/kg bw
Basis:
nominal conc.

No. of animals per sex per dose:

20

Control animals:

yes, historical

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes

BODY WEIGHT: Yes

HAEMATOLOGY: Yes

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes: lungs, spleen, kidneys, liver, mamma, testes, uterus, ovaries.

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:

not specified

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

not specified

Ophthalmological findings:

not specified

Haematological findings:

no effects observed

Clinical biochemistry findings:

not specified

Urinalysis findings:

not specified

Behaviour (functional findings):

not specified

Organ weight findings including organ / body weight ratios:

not specified

Gross pathological findings:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

no effects observed

Details on results:

CLINICAL SIGNS AND MORTALITY
No overt clinical signs or changes in behavior or mortality were observed in the test group.

BODY WEIGHT AND WEIGHT GAIN
After administration of the test substance for 24 months, body weights were comparable with those of controls.

HAEMATOLOGY
Hematological and electrophoretic investigations did not show leukosis in any animal. In animals with chronic bronchopneumonia, hyperleukocytosis with polynucleosis and hypergammaglobulinemia were found.

GROSS PATHOLOGY
At autopsy the macroscopical findings were one benign mammary tumor at the left fossa ilia in one male, a small ovarian cyst in one female, and an increase in the size of one ovary in another female. In the lungs of several male and female rats the signs of a chronic bronchopneumonia were observed.

HISTOPATHOLOGY: NON-NEOPLASTIC
The histopathological examinations of the preserved tissues did not revealed treatment-related effects (s. table). Most adverse effects were inflammatory or were classified as spontaeous changes.

HISTORICAL CONTROL DATA (if applicable)
A benign mammary tumor had been observed in historical controls. This tumor was, therefore, considered to be incidental and not related to the treatment. The historical data on this strain at an age of two years have demonstrated an incidence of tumors of the pituitary of less than 5% and of sarcomas of less than 3%. Cutaneous papillomatosis was also observed.

Any other information on results incl. tables

Histopathology for rats fed 100 mg/kg bw Aerosil R 972 for 2 years

	No. of rats with lesions
Organs and lesions	Males	Females
Lungs: Peribronchial lymphoid tissue, hyperplastic Dilatation bronchi Emphysema foci Focal suppuration	7/20 7/20 7/20 1/20	7/20 7/20 5/20 1/20
Spleen: Lymphoid tissue, hyperplastic Red pulpa, increase of plasma cells Red pulpa, reactive	2/20 7/20 5/20	2/20 6/20 4/20
Kidneys: Renal tubules, dilatation Granular cylinders	4/20 3/20	3/20 1/20
Liver: Inflammatory infiltration		1/20
Mamma: Fibrotic adenoma, benign	1/20
Testes: Seminiferous tubules, atrophic Glandular tissue, hyperplastic (not tumors)	1/20 1/20
Uterus: Mucous membrane, hyperplastic (slight degree)		2/20
Ovaries: Atresic follicles Interstitial gland, hyperplastic Serous cyst, benign		2/20 2/20 1/20

Comparison of the rates of tumors found in the study with those occurring in historical controls indicated that no carcinogenic effects could be attributed to the exposure.