Silicon dioxide

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

The dataset for covering the endpoint in vitro genotoxicity of untreated (hydrophilic) SAS compiles 9 studies performed with different hydrophilic forms of the substance and BET values ranging from 30 to 420 m²/g. Several different test methods were used, and all studies meet the criteria of Klimisch score 1 or 2.

5 Bacterial reverse mutation assays were carried out, all under GLP, according to OECD TG 471 or similar protocols, both with and without metabolic activation. All these studies were negative.

Using mammalian cells, 2 chromosome aberration assays were carried out according to OECD TG 473 or similar protocols, both with and without metabolic activation and one under GLP. All results were negative.

One Gene mutation testing on mammalian cells was carried out according to EPA OPP 84-2 under GLP. No positive effects were detected in this study.

One additional test for Unscheduled DNA Synthesis (UDS) carried out, under GLP, with rat primary hepatocytes according to OECD TG 482 yielded negative results.

Link to relevant study records

Reference

Reference 1

Endpoint:

in vitro gene mutation study in mammalian cells

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Nov. 20-27, 1989

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EPA OPP 84-2

Principles of method if other than guideline:

8 dose l., 5h duration, w & w/o S9-activation, 7d post obs.

GLP compliance:

yes (incl. QA statement)

Type of assay:

in vitro mammalian cell gene mutation test using the Hprt and xprt genes

Specific details on test material used for the study:

synthetic amorphous silicon dioxide CAB-O-SIL EH-5

Species / strain / cell type:

Chinese hamster Ovary (CHO)

Details on mammalian cell type (if applicable):

CHO-K1-BH4 cells were obtained directly from Dr. Abraham Hsie, Oak Ridge National Laboratories, Oak Ridge, TN, USA. The freeze lot of cells was tested and found to be free of mycoplasma using both the agar culture and Hoechst stainibg procedures.

Metabolic activation:

with and without

Metabolic activation system:

S9 mix.

Test concentrations with justification for top dose:

50, 100, 150 ,200, 250, 300, 400, 500 µg/ml

Vehicle / solvent:

The treatment medium consisted of 4 ml F12FBS5-Hx containing various concentrations of test article and 1 ml S-9 reaction mixture for the activated study and 5 ml F12FBS5-Hx containing various concentrations of test article for the non-activated study. The final solvent concentration in the culture medium was 1% by volume.

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

Positive controls:

yes

Positive control substance:

benzo(a)pyrene

ethylmethanesulphonate

Key result

Species / strain:

Chinese hamster Ovary (CHO)

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Additional information on results:

The cytotoxic effects (concurrent cytototoxicity) of a 5 hour treatment of CHO cells in the presence ad absence of an exogenous metabolic activation system are presented in Table 2. Mutagenicity data are presented in Tables 3 and 4.

Conclusions:

synthetic amorphous silicon dioxide Cab-O-Sil EH-5 was negative in the CHO/HGPRT mutation assay both with and without metabolic activation.

Executive summary:

synthetic amorphous silicon dioxide CAB-O-SIL EH-5C was tested according to EPA guideline OPP 84 -2 under GLP conditions

Reference 2

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Qualifier:

equivalent or similar to guideline

Guideline:

JAPAN: Guidelines for Screening Mutagenicity Testing Of Chemicals

Qualifier:

equivalent or similar to guideline

Guideline:

EU Method B.13/14 (Mutagenicity - Reverse Mutation Test Using Bacteria)

GLP compliance:

yes

Type of assay:

bacterial reverse mutation assay

Specific details on test material used for the study:

surface treated synthetic amorphous silicon dioxide RA200HS

Species / strain / cell type:

S. typhimurium TA 1535, TA 1537, TA 98 and TA 100

Species / strain / cell type:

E. coli WP2 uvr A

Metabolic activation:

with and without

Metabolic activation system:

S-9 mix obtained from Aroclor 1254 treated male Sprague-Dawley rats' livers.

Test concentrations with justification for top dose:

50, 150, 500, 1500, 5000 µg/plate
up to maximum recommended dose level

Vehicle / solvent:

ethanol

Negative solvent / vehicle controls:

yes

Positive controls:

yes

Positive control substance:

4-nitroquinoline-N-oxide

9-aminoacridine

N-ethyl-N-nitro-N-nitrosoguanidine

other: Aminoanthracene

Key result

Species / strain:

S. typhimurium TA 98

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not determined

Vehicle controls validity:

valid

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 100

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not determined

Vehicle controls validity:

valid

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 1535

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not determined

Vehicle controls validity:

valid

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 1537

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not determined

Vehicle controls validity:

valid

Positive controls validity:

valid

Key result

Species / strain:

E. coli WP2 uvr A

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not determined

Vehicle controls validity:

valid

Positive controls validity:

valid

Additional information on results:

No significant increase in the frequency of revertant colonies was recorded for any of the bacterial strains with any dose of the test material either with or without metabolic activation.

Conclusions:

surface treated synthetic amorphous silicon dioxide RA200HS was not mutagenic under the test conditions

Executive summary:

An Ames test in S. typhimurium and E coli was conducted with surface treated synthetic amorphous silicon dioxide RA200HS.

Reference 3

Endpoint:

in vitro DNA damage and/or repair study

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

Nov. 28 - Dec. 22, 1989

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.5550 - Unscheduled DNA Synthesis in Mammalian Cells in Culture

Qualifier:

according to guideline

Guideline:

EPA OPP 84-2

GLP compliance:

yes (incl. QA statement)

Type of assay:

other: UDS assay

Specific details on test material used for the study:

synthetic amorphous silicon dioxide CAB-O-SIL EH-5

Species / strain / cell type:

hepatocytes:

Details on mammalian cell type (if applicable):

primary rat hepatocytes derived from the livers of normal adult male Fischer 344 rats

Metabolic activation:

without

Test concentrations with justification for top dose:

0.3, 1.0, 3, 10, 30, 100, 300, 1000 µg/ml

Vehicle / solvent:

DMSO

Negative solvent / vehicle controls:

yes

Positive controls:

yes

Positive control substance:

7,12-dimethylbenzanthracene

Details on test system and experimental conditions:

treated for 18-20 hrs

Key result

Species / strain:

hepatocytes:

Metabolic activation:

without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Positive controls validity:

valid

Additional information on results:

synthetic amorphous silicon dioxide Cab-O-Sil EH-5 did not cause any significant increase in unscheduled DNA synthesis as measured by the mean number of net nuclear grain counts, at any dose level.
cf. tables 2 & 3 for more details on results

Conclusions:

synthetic amorphous silicon dioxide Cab-O-Sil EH-5 was negative in the UDS assay under the test conditions,

Executive summary:

An unschedulded DNA synthesis assay was conducted with synthetic amorphous silicon dioxide Cab-O-Sil EH-5 in rat primary hepatocyte cells.

Reference 4

Endpoint:

in vitro cytogenicity / chromosome aberration study in mammalian cells

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

Dec. 1, 1989 - Feb. 20, 1990

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EPA OPP 84-2

Principles of method if other than guideline:

(9 dose l., 15-18h duration, w & w/o S9-activation)

GLP compliance:

yes (incl. QA statement)

Type of assay:

in vitro mammalian chromosome aberration test

Specific details on test material used for the study:

synthetic amorphous silicon dioxide Cab-O-Sil EH-5

Species / strain / cell type:

Chinese hamster Ovary (CHO)

Metabolic activation:

with and without

Metabolic activation system:

S9 mix.

Test concentrations with justification for top dose:

non-activated: 19, 38, 75, 150, 300 µg/ml
activated: 250, 500, 750, 1000 µg/ml

Vehicle / solvent:

DMSO

Negative solvent / vehicle controls:

yes

Positive controls:

yes

Positive control substance:

triethylenemelamine

cyclophosphamide

Details on test system and experimental conditions:

Cells were collected for evaluation at 18 or 15 hours after treatment in the non-achtivated or S-9 activated system, respectively

Key result

Species / strain:

Chinese hamster Ovary (CHO)

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Positive controls validity:

valid

Additional information on results:

cf. tables 3 & 4 for more details

Conclusions:

synthetic amorphous silicon dioxide Cab-O-Sil EH-5 was negative in the CHO cytogenetics assay.

Executive summary:

synthetic amorphous silicon dioxide Cab-O-Sil EH-5 was tested in a chromosome aberration test using Chinese hamster ovary cells.

Reference 5

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

Nov. 20 - Dec. 28, 1989

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

EPA OPP 84-2

Deviations:

yes

Remarks:

vehicle control in TA100 strain test

Principles of method if other than guideline:

Ames test in salmonella, w & w/o S9-activation

GLP compliance:

yes (incl. QA statement)

Type of assay:

bacterial reverse mutation assay

Specific details on test material used for the study:

synthetic amorphous silicon dioxide Cab-O-Sil EH-5

Species / strain / cell type:

S. typhimurium TA 1535, TA 1537, TA 98 and TA 100

Species / strain / cell type:

S. typhimurium TA 1538

Metabolic activation:

with and without

Metabolic activation system:

S9 mix

Test concentrations with justification for top dose:

667, 1000, 3333, 6667, 10000 µg/plate

Vehicle / solvent:

DMSO

Negative solvent / vehicle controls:

yes

Positive controls:

yes

Positive control substance:

2-nitrofluorene

sodium azide

other: 2-aminoanthracene, ICR-191

Key result

Species / strain:

S. typhimurium TA 98

Metabolic activation:

with and without

Genotoxicity:

negative

Vehicle controls validity:

valid

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 100

Metabolic activation:

with and without

Genotoxicity:

negative

Vehicle controls validity:

not valid

Remarks:

however vehicle control plated with another study on the same day was acceptable

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 1535

Metabolic activation:

with and without

Genotoxicity:

negative

Vehicle controls validity:

valid

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 1537

Metabolic activation:

with and without

Genotoxicity:

negative

Vehicle controls validity:

valid

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 1538

Metabolic activation:

with and without

Genotoxicity:

negative

Vehicle controls validity:

valid

Positive controls validity:

valid

Conclusions:

synthetic amorphous silicon dioxide was not mutagenic tunder the test conditions

Executive summary:

An Ames test was conducted with synthetic amorphous silicon dioxide Cab-O-Sil EH-5.

Reference 6

Endpoint:

in vitro cytogenicity / chromosome aberration study in mammalian cells

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 473 (In Vitro Mammalian Chromosome Aberration Test)

Deviations:

yes

Remarks:

without external metabolic activation system

Principles of method if other than guideline:

Method: Culture technique, determination of cytotoxicity and test for chromosomal aberrations decribed and similar to current guideline (OECD 473)

GLP compliance:

no

Type of assay:

in vitro mammalian chromosome aberration test

Specific details on test material used for the study:

synthetic amorphous silicon dioxide Syloid 244

Species / strain / cell type:

other: Human embryonic lung cells (WI-38)

Metabolic activation:

without

Test concentrations with justification for top dose:

0.1, 1.0, and 10 µg/ml (note: mcg/ml is stated: Tab. Test I, p. 83)
Dose selection: 10 µg/ml was the highest level free of observable cell clumping (see Report p. 6/7).

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: water, 0.85 % saline
- Justification for choice of solvent/vehicle: suspension

Negative solvent / vehicle controls:

yes

Remarks:

saline

Positive controls:

yes

Positive control substance:

triethylenemelamine

Remarks:

Migrated to IUCLID6: 0.1 µg/ml

Details on test system and experimental conditions:

METHOD OF APPLICATION: in suspension, 5 x10^5 cells/mL
Mutations were quantified by counting anaphase aberrations.

DURATION
- Incubation temperature: 37 °C
- Exposure duration: 24 - 48 h

Fixation: absolute methanol:glacial acetic acid (3:1) for 30 min after centrifugation
STAIN (for cytogenetic assays): acetic acid-orcein stain (2.0 %)

NUMBER OF REPLICATIONS: 3/dose level

NUMBER OF CELLS EVALUATED: 100/dose level

DETERMINATION OF CYTOTOXICITY
- Method: mitotic index; other: "any cytopathic effect" at 24, 48, and 72 h after exposure to dose levels logarithmatically spaced


OTHER EXAMINATIONS:
- Determination of polyploidy: yes

Metabolic activation:

without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not specified

Remarks:

"clumping" of cells as criterion for maximum dose selection

Vehicle controls validity:

valid

Untreated negative controls validity:

not examined

Positive controls validity:

valid

Anaphase aberrations (from Report Table p. 83)

	Mitotic index^1)	No. of cells	% cells with acentric frag.	% cells with bridges	% multipolar cells	% cells other aberr.^2)	% cells with aberr.
Syloid
0.1 µg/mL	3	100	3	0	0	0	3
1.0 µg/mL	4	100	4	1	0	0	5
10.0 µg/mL	4	100	0	0	0	0	0
Saline	3	100	1	0	0	0	1
TEM (0.1 µg/mL)	2	100	13	4	1	3 (pp)	21

¹⁾ % cells in mitosis: 200 cells observed/dose level

²⁾ Cells with polyploidy, pulverisation (pp), or greater than 10 aberrations

Conclusions:

synthetic amorphous silicon dioxide Syloid 244 was negative in human embryonic lung cells

Executive summary:

The genetic toxicity potential of synthetic amorphous silicon dioxide Syloid 244 was studied in human embryonic lung cells (WI-38).

Reference 7

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

Jul. 12 - Oct. 31, 1978

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

test procedure in accordance with national standard methods with acceptable restrictions

Qualifier:

no guideline available

Principles of method if other than guideline:

Ames test in salmonella, w & w/o S9-activation

GLP compliance:

no

Type of assay:

bacterial reverse mutation assay

Specific details on test material used for the study:

synthetic amorphous silicon dioxide Cab-O-Sil M5

Species / strain / cell type:

S. typhimurium TA 1535, TA 1537, TA 98 and TA 100

Species / strain / cell type:

S. typhimurium TA 1538

Metabolic activation:

with and without

Metabolic activation system:

not specified

Test concentrations with justification for top dose:

5 mg

Vehicle / solvent:

DMSO

Negative solvent / vehicle controls:

yes

Positive controls:

yes

Positive control substance:

methylmethanesulfonate

other: 2-aminofluorene

Species / strain:

S. typhimurium TA 98

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not determined

Vehicle controls validity:

valid

Positive controls validity:

valid

Species / strain:

S. typhimurium TA 100

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not determined

Vehicle controls validity:

valid

Positive controls validity:

valid

Species / strain:

S. typhimurium TA 1535

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not determined

Vehicle controls validity:

valid

Positive controls validity:

valid

Species / strain:

S. typhimurium TA 1537

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not determined

Vehicle controls validity:

valid

Positive controls validity:

valid

Species / strain:

S. typhimurium TA 1538

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not determined

Vehicle controls validity:

valid

Positive controls validity:

valid

Additional information on results:

cf. illustration below for details

Conclusions:

synthetic amorphous silicon dioxide Cab-O-Sil M5 did not cause a positive response with any of the tester strains in the presence or absence of Aroclor-induced rat liver S9.

Executive summary:

An Ames test in five salmonella strains was conducted with synthetic amorphous silicon dioxide Cab-O-Sil M5.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Genetic toxicity in vivo

Description of key information

The in vivo genotoxicity potential of untreated (hydrophilic) SAS was evaluated in 3 studies launched from 1974 to 2000 with materials having BET range from 175 to 349 m²/g. All these studies meet the criteria of Klimisch score 2.

A rodent dominant lethal test (similar to OECD guideline 478), was performed in 1974 on the substance and no mutagenic potential was detected.

A Mammalian bone marrow chromosome aberration was performed according to OECD 475 and no genotoxicity was detected. No genotoxic effects in alveolar epithelial cells occurred in an ex-vivo/in-vitro HPRT assay.

Link to relevant study records

Reference

Reference 1

Endpoint:

in vivo mammalian somatic cell study: cytogenicity / bone marrow chromosome aberration

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 475 (Mammalian Bone Marrow Chromosome Aberration Test)

GLP compliance:

no

Type of assay:

chromosome aberration assay

Specific details on test material used for the study:

synthetic amorphous silicon dioxide Syloid 244

Species:

rat

Strain:

Sprague-Dawley

Sex:

male

Route of administration:

oral: gavage

Vehicle:

- vehicle: 0.85 % saline
- Volume of the vehicle: no data
- Justification for choice of solvent/vehicle: no data
- Concentration of test material in vehicle: no data


MAXIMUM DOSE VOLUME APPLIED: no data

Details on exposure:

3 time points: sampling at 6, 24, and 48 h in the single-dose study
1 time point: sampling at 6 h after the last dose in the repeated-dose study

Colcemide (4 mg/kg bw i.p) was given 2 h prior to kill.

Duration of treatment / exposure:

single administration (acute) and repeated administration (5 times, subacute)

Frequency of treatment:

1x, and 5x(1x/d)

Dose / conc.:

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

Dose / conc.:

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

Dose / conc.:

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

Dose / conc.:

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

Dose / conc.:

5 000 mg/kg bw/day (nominal)

No. of animals per sex per dose:

5; but 3 as vehicle control

Control animals:

yes, concurrent vehicle

Positive control(s):

triethylenemelamine
- Route of administration: i.p.
- Doses / concentrations: 0.3 mg/kg bw

Tissues and cell types examined:

bone-marrow cells

Sex:

male

Genotoxicity:

negative

Toxicity:

not specified

Vehicle controls validity:

valid

Positive controls validity:

valid

Conclusions:

synthetic amorphous silicon dioxide Syloid 244 was negativein in in vivo chromosome aberration test.

Executive summary:

An in vivo chromosome aberration test similar to OECD 475 was conducted with synthetic amorphous silicon dioxide Syloid 244

Reference 2

Endpoint:

in vivo mammalian germ cell study: gene mutation

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: well documented research study

Reason / purpose for cross-reference:

reference to same study

Reason / purpose for cross-reference:

reference to same study

Qualifier:

no guideline available

Principles of method if other than guideline:

Method: ex-vivo/in-vitro HPRT mutation assay, no standard guideline available.

GLP compliance:

not specified

Type of assay:

other: mammalian cell gene mutation assay: ex-vivo/in-vitro HPRT assay

Specific details on test material used for the study:

synthetic amorphous silicon dioxide AEROSIL 200

Species:

rat

Strain:

Fischer 344

Sex:

male

Details on test animals or test system and environmental conditions:

Weight at study initiation: 200 - 250 g

Route of administration:

inhalation

Details on exposure:

TYPE OF INHALATION EXPOSURE: whole body

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: 300-L horizontal laminar-flow chamber, compartmentalised
- System of generating particulates/aerosols: srew-feed mechnaism (ACCURate, Whitewater) in combination with a Venturi-type dust feeder
- Temperature, humidity, pressure in air chamber: no data
- Air flow rate: no data
- Air change rate: no data
- Method of particle size determination: no data

Duration of treatment / exposure:

13 wks

Frequency of treatment:

6 h/d, 5 d/wk

Post exposure period:

3 and 8 months

Dose / conc.:

50.4 mg/m³ air (analytical)

Remarks:

50.4 +/- 19-0 mg/m³

No. of animals per sex per dose:

no data, only males, probably 4 animals per endpoint

Control animals:

yes, sham-exposed

Positive control(s):

Crystalline silica was examined simulataneously and showed genotoxic effects in alveolar epithelial cells.

Tissues and cell types examined:

The testing programme included cellular and biochemical Bronchoalveolar Lavage Fluid Analysis (BLA) on inflammatory markers, histopathology, inflammatory cytokine gene expression, immunohistochemisty for DNA damage, and mutagenesis in alveolar epithelial cells. 

Statistics:

Analysis of variance, Dunnett´s test for determination of differences between control and treated groups.

Key result

Sex:

male

Genotoxicity:

negative

Remarks:

Alveolar type-II cells isolated from the 50-mg/m3 rat group showed no increased mutation frequency as compared to the control.

Toxicity:

yes

Remarks:

inflammation; but inflammation is not responsible for the development of mutagenic effects in rat lungs alter high doses of particle exposures

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

After 13 weeks of exposure, lavage neutrophils were increased from 0.26% (controls) to 55% of total lavaged cells for amorphous silica, with significantly greater lavage neutrophil numbers. BAL fluid levels of LDH as an indicator of cytotoxicity were high for amorphous silica, at the end of exposure. All parameters decreased rapidly for amorphous silica in the 8-month recovery period. Increased MIP-2 expression was observed at the end of the exposure period for amorphous silica. After 8 months of recovery, those markers were not significantly different from controls. No significant increase in HPRT mutation frequency in alveolar epithelial cells was detected after 13 weeks of exposure to amorphous silica. A significant, increase in TUNEL staining was detected in macrophages and terminal bronchiolar epithelial cells of amorphous silica-exposed rats at the end of the exposure period. However, no genotoxic effects in alveolar epithelial cells occurred after amorphous silica exposure, despite a high degree of infammatory-cell response.

Conclusions:

Despite a high degree of infammatory-cell response, no genotoxic effects in alveolar epithelial cells occurred after exposure of synthetic amorphous silicon dioxide AEROSIL 200

Executive summary:

This is the main part of a comparative study including synthetic amorphous and crystalline silica. Here only the mutagenic effects of Aerosil 200 (amorphous) are documented.

Reference 3

Endpoint:

in vivo mammalian germ cell study: cytogenicity / chromosome aberration

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 478 (Genetic Toxicology: Rodent Dominant Lethal Test)

GLP compliance:

no

Type of assay:

rodent dominant lethal assay

Specific details on test material used for the study:

synthetic amorphous silicon dioxide Syloid 244

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Route of administration:

oral: gavage

Vehicle:

- vehicle: 0.85 % saline
- Volume of the vehicle: no data
- Justification for choice of solvent/vehicle: no data
- Concentration of test material in vehicle: no data


MAXIMUM DOSE VOLUME APPLIED: no data

Duration of treatment / exposure:

single administration (acute) and repeated administration (5 times, subacute)

Frequency of treatment:

5x (1x/day)

Remarks:

Doses / Concentrations:
1.4, 14.0, 140, 500 and 5000 mg/kg suspended in 0.85 % saline
Basis:

Dose / conc.:

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

Dose / conc.:

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

Dose / conc.:

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

Dose / conc.:

500 mg/kg bw/day (nominal)

Dose / conc.:

5 000 mg/kg bw/day (nominal)

No. of animals per sex per dose:

10 males (treated) mated to virgin female rats (2 females/1 male)

Control animals:

yes, concurrent vehicle

yes, historical

Positive control(s):

triethylene melamine
- Route of administration: i.p.
- Doses / concentrations: 0.3 mg/kg bw

Sex:

male/female

Genotoxicity:

negative

Vehicle controls validity:

valid

Negative controls validity:

valid

Positive controls validity:

valid

Acute: Some changes were observed in the low and mid dose
group. In the high dose (5000 mg/kg bw), no significant changes 

were seen.

Subacute: In the intermittent dose groups of test series I significant decreases were seen in fertility index and number of implants in week 5 (Report Tab. I, p. 100).
Dose related decreases were observed in corpora lutea
(week 5) and dead implants/pregnant female in week 4. Dose
related increases were seen in corpora lutea (week 3),
preimplantation loss (week 2, 3)(Report, Tab. II - VIII, p.101 -107).

But no consistently significant effects were noted at the two highest doses (500 and 5000 mg/kg bw) in test series II. A time trend pattern was not found either.

The positive control(triethylene melamine) administered as a single

i.p. dose to males produced a slight decrease in mean number of

implantations per litter (wk 1 - 3) [Report, Tab. II, p. 93] and

significant increases in dead implants and in preimplantation losses

from post-treatment week 1 through 4 (Report,"acute study", Tab. II - VIII, p. 93 -99] without affecting the fertility index (Report, Tab. I, p.92).
  --------------

Conclusions:

synthetic amorphous silicon dioxide Syloid 244 was not mutagenic

Executive summary:

A dominant lethal assay study was conducted with synthetic amorphous silicon dioxide Syloid 244 in rats to assess its mutagenic potential.

Reference 4

Endpoint:

genetic toxicity in vivo, other

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Justification for type of information:

a gene mutation in mammalian cells and a study with rat primary hepatocytes both yielded negative results.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Justification for classification or non-classification

Available studies did not identify any potential towards genotoxicity. According to Annex I of the Regulation (EC) 1272/2008 (table 3.5.1) and GHS (Globally Harmonized Classification System), the test substance requires no classification and has no mandatory label requirement.