Cordierite (Mg2[Al4O3(SiO3)5])

Endpoint summary

Description of key information

Repeated-dose toxicity study by oral route has been performed on synthetic amorphous silica (SAS) as a read-across substance representing a worst-case scenario, according to a method similar to 453, on rats which is the preferred species for this study. The NOAEL was 5% of the substance in diet, which corresponds to a dose between 1700 and 3000 mg/kg bw/day for both male and female rats and is the highest concentration evaluation during this study. As it is the lowest actual dose received, the NOAEL for repeated dose toxicity by oral route has been determined to be 1600 mg/kg bw/day.

Repeated-dose toxicity study by oral route has been performed on synthetic SAS as a read-across substance representing a worst-case scenario, according to a method similar to 413, on rats which is the preferred species for this study. The NOAEL has been determined to be 31 mg/m3 for systemic effects, and 1.3 mg/m3 for local effects.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Reference 1

Endpoint:

chronic toxicity: oral

Remarks:

combined repeated dose and carcinogenicity

Type of information:

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

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study was conducted using a method equivalent to OECD Testing Guideline 453 and meets acceptable scientific standards.

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 453 (Combined Chronic Toxicity / Carcinogenicity Studies)

Deviations:

yes

Remarks:

no urinalysis was performed

GLP compliance:

no

Limit test:

yes

Species:

rat

Strain:

Fischer 344

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Funabashifarm Animal Co. Ltd., Japan
- Age at study initiation: 3 weeks
- Weight at study initiation: male: 117g to 150g; female: 92.0g to 126g
- Fasting period before study: Not provided
- Housing: 2 animals per cage
- Diet: ad libitum
- Water: ad libitum
- Acclimation period: 2 weeks

ENVIRONMENTAL CONDITIONS
- Temperature: 23 +/- 1°C
- Humidity: 50 +/- 10%
- Air changes (per hr): Not provided
- Photoperiod: 10 hrs dark / 14 hrs light

Route of administration:

oral: feed

Vehicle:

unchanged (no vehicle)

Details on oral exposure:

DIET PREPARATION
- Rate of preparation of diet (frequency): weekly

Analytical verification of doses or concentrations:

no

Duration of treatment / exposure:

Duration: 103 weeks. Some specimens were sacrificed after 6 and 12 months.

Frequency of treatment:

Continuous administration through diet.

Remarks:

Doses / Concentrations:
1.25, 2.5 and 5 %
Basis:
nominal in diet

No. of animals per sex per dose:

40 animals per sex for 1.25%, 2.5%, and the control. 41 animals per sex for 5%.

Control animals:

yes, plain diet

Observations and examinations performed and frequency:

Physical examinations and observations:
- Survival: daily
- Body weights: weekly for the first 55 weeks then biweekly
- Food consumption: weekly
- Unusual signs: routinely
- Other: some specimen were sacrificed to collect experimental data after 26 and 52 weeks.

Clinical laboratory procedure:
- Haematology: Erythrocytes, haemoglobin, leukocytes, and haematocrit at termination
- Clinical chemistry: aspartate transaminase, alanine transaminase, serum inorganic phosphorus, total protein, albumin, lactic dehydrogenase, alkali phosphatase, total bilirubin, total cholesterol, high density lipoprotein cholesterol, low density lipoprotein cholesterol, triglyceride, , blood urea nitrogen, uric acid, creatinine, and calcium on serum separated from the blood after clotting at termination

Sacrifice and pathology:

- Sacrifice: by etherization after overnight fasting.
- Gross examination: lungs, bronchus, heart, kidneys, liver, spleen, brain, stomach, colon, intestines, pancreas, adrenal glands, pituitary, thyroid, salivary glands, thymus, testes, prostate, bladder, ovaries, uterus, oviducts, femoral bones, mammary glands, skin, and subcutis.
- Microscopic examination: liver, kidneys, spleen, heart, and brain fixed in cold, neutrally-buffered solution of formalin, embedded in paraffin, sectioned, and stained with hematoxylin-eosin

Statistics:

Significance of differences tested by using Student's t-analysis variance test.
Chi-square test of significance (p<0.05) by Mantel-Hanszel was employed to compare the survival date exclusive of sacrificed specimens.
Prevalence rates expressed as percentages of tumor groups and non-tumor groups.
Significance of differences between means of prevalence tested by using Fischer's exact test.
Percentages of frequencies of tumor analyzed by using the Cochran-Armitage test for trend in proportion.

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):

no effects observed

Food efficiency:

not examined

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

not examined

Ophthalmological findings:

not examined

Haematological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

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:

CLINICAL SIGNS AND MORTALITY
- Deaths in male groups compared to control group (non-significant)
- Highest survival rates in the 5% group (non dose-related)

FOOD CONSUMPTION AND COMPOUND INTAKE
Mean cumulative intake of the substance at the end of the 103 weeks:
- 1.25%: 143.46g (male) and 107.25g (female)
- 2.5%: 179.55g (male) and 205.02g (female)
- 5%: 581.18g (male) and 435.33g (female)

HAEMATOLOGY
- Sporadic variations in haematologic profiles observed in the treated groups (non-significant)

CLINICAL CHEMISTRY
- Changes observed in aspartate transaminase, albumin, alanine transaminase, lactic dehydrogenase, total protein, total bilirubin, low-density lipoprotein cholesterol, and triglyceride (non biologically significant)
- No changes observed in creatinine, urea, and bilirubin.

ORGAN WEIGHTS
- Lower liver weight noted from 52 weeks to 103 weeks in female rats compared with treated groups dosed at 2.5% and 5% (non sex or dose-related)
- No sex or dose-related hypertrophy or atrophy.

HISTOPATHOLOGY: NEOPLASTIC
- Greatest tumor incidence in genital organs (non significant)
- Relatively low incidence in other organs (non significant)

Dose descriptor:

NOAEL

Remarks:

highest dose evaluated

Effect level:

ca. 1 700 - ca. 3 000 mg/kg bw/day (actual dose received)

Sex:

male

Basis for effect level:

other: highest dose evaluated: 5% concentration in diet

Dose descriptor:

NOAEL

Remarks:

highest dose evaluated

Effect level:

ca. 1 700 - ca. 3 000 mg/kg bw/day (actual dose received)

Sex:

female

Basis for effect level:

other: highest dose evaluated: 5% concentration in diet

Critical effects observed:

not specified

Conclusions:

The NOAEL was 5% of the substance in diet, which corresponds to a dose between 1700 and 3000 mg/kg bw/day for both male and female and is the highest concentration evaluation during this study.

Executive summary:

Chronic toxicity of the read-across substance silicon dioxide branded as Syloid 244 following an oral exposure was determined according to a method similar to the OECD Guideline for Testing of chemicals 453. Syloid 244 was orally administrated in diet to Fisher rats - which is the preferred species for this study - for 103 weeks at dose levels of 0, 1.25, 2.5, and 5%. Clinical observations were performed routinely throughout the study. Body weight were calculated weekly for the first 55 weeks then biweekly. Food consumption was determined weekly. Haematology and clinical chemistry was performed at termination.

Lungs, bronchus, heart, kidneys, liver, spleen, brain, stomach, colon, intestines, pancreas, adrenal glands, pituitary, thyroid, salivary glands, thymus, testes, prostate, bladder, ovaries, uterus, oviducts, femoral bones, mammary glands, skin, and subcutis were extracted for gross examination. Microscopic examination was performed on liver, kidneys, spleen, heart, and brain.

Animals were sacrificed after 6 and 12 months to obtain additional intermediate data.

No significant or dose-related alterations were observed in food consumption, body and organ weights, haematology, clinical chemistry, and during the histopathology.

The NOAEL was 5% of the substance in diet, which corresponds to a dose between 1700 and 3000 mg/kg bw for both male and female and is the highest concentration evaluation during this study.

Reference 2

Endpoint:

chronic toxicity: oral

Remarks:

combined repeated dose and carcinogenicity

Type of information:

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

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study was conducted using a method equivalent to OECD Testing Guideline 453 and meets acceptable scientific standards.

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 453 (Combined Chronic Toxicity / Carcinogenicity Studies)

Deviations:

yes

Remarks:

no urinalysis was performed

GLP compliance:

no

Limit test:

yes

Species:

mouse

Strain:

B6C3F1

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Funabashifarm Animal Co. Ltd., Japan
- Age at study initiation: 4 weeks
- Weight at study initiation: male: 21.0g to 27.3g; female: 16.0g to 19.9g
- Fasting period before study: Not provided
- Housing: 5 animals per cage
- Diet: ad libitum
- Water: ad libitum
- Acclimation period: 1 week

ENVIRONMENTAL CONDITIONS
- Temperature: 23 +/- 1°C
- Humidity: 50 +/- 10%
- Air changes (per hr): Not provided
- Photoperiod: 10 hrs dark / 14 hrs light

Route of administration:

oral: feed

Vehicle:

unchanged (no vehicle)

Duration of treatment / exposure:

Duration: 93 weeks. Some specimens were sacrificed after 6 and 12 months.

Frequency of treatment:

Continuous administration through diet.

Remarks:

Doses / Concentrations:
1.25, 2.5 and 5 %
Basis:
nominal in diet

No. of animals per sex per dose:

40 male animals for 1.25%, 2.5%, 5%, and the control. 40 female animals for 1.25%, 2.5%, and 5%. 38 female animals for the control.

Control animals:

yes, plain diet

Observations and examinations performed and frequency:

Physical examinations and observations:
- Survival: daily
- Body weights: weekly for the first 55 weeks then biweekly
- Food consumption: weekly
- Unusual signs: routinely
- Other: some specimen were sacrificed to collect experimental data after 26 and 52 weeks.

Clinical laboratory procedure:
- Haematology: Erythrocytes, haemoglobin, leukocytes, and haematocrit at termination
- Clinical chemistry: aspartate transaminase, alanine transaminase, serum inorganic phosphorus, total protein, albumin, lactic dehydrogenase, alkali phosphatase, total bilirubin, total cholesterol, high density lipoprotein cholesterol, low density lipoprotein cholesterol, triglyceride, , blood urea nitrogen, uric acid, creatinine, and calcium on serum separated from the blood after clotting at termination

Sacrifice and pathology:

- Sacrifice: by etherization after overnight fasting.
- Gross examination: lungs, bronchus, heart, kidneys, liver, spleen, brain, stomach, colon, intestines, pancreas, adrenal glands, pituitary, thyroid, salivary glands, thymus, testes, prostate, bladder, ovaries, uterus, oviducts, femoral bones, mammary glands, skin, and subcutis.
- Microscopic examination: liver, kidneys, spleen, heart, and brain fixed in cold, neutrally-buffered solution of formalin, embedded in paraffin, sectioned, and stained with hematoxylin-eosin

Statistics:

Significance of differences tested by using Student's t-analysis variance test.
Chi-square test of significance (p<0.05) by Mantel-Hanszel was employed to compare the survival date exclusive of sacrificed specimens.
Prevalence rates expressed as percentages of tumor groups and non-tumor groups.
Significance of differences between means of prevalence tested by using Fischer's exact test.
Percentages of frequencies of tumor analyzed by using the Cochran-Armitage test for trend in proportion.

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

no effects observed

Food efficiency:

not examined

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

not examined

Ophthalmological findings:

not examined

Haematological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

no effects observed

Histopathological findings: non-neoplastic:

no effects observed

Histopathological findings: neoplastic:

no effects observed

Details on results:

CLINICAL SIGNS AND MORTALITY
- No significant difference in survival rates.

BODY WEIGHT AND WEIGHT GAIN
- Control and treated groups grew at a similar rate during the first 61 weeks.
- Variations in body weights observed at 1.25% and 2.5% (non-significant).
- Lower growth rate compared to the control at the end of the first 10 weeks at 5%.
- Increase of the food consumption compared to the control group noted at 2.5% and 5% after 81 weeks.

FOOD CONSUMPTION AND COMPOUND INTAKE
Mean cumulative intake of the substance at the end of the 103 weeks:
- 1.25%: 38.45g (male) and 37.02g (female)
- 2.5%: 79.78g (male) and 72.46g (female)
- 5%: 5160.25g (male) and 157.59g (female)

HAEMATOLOGY
- Lower haematrocrit and mean corpuscular volume after 52 weeks in the treated groups (non dose-related)
- No dose-related alteration of haematologic profiles at the end of the 52 and 93 weeks.

ORGAN WEIGHTS
- Sporadic abnormal atrophy or hypertrophy of the organs found in the animals treated for 26 weeks at 2.5% and 5% (non sex or dose-related)

HISTOPATHOLOGY: NEOPLASTIC
- Tumors found in the haematopoietic organs in the female mice treated at 2.5% (non-significant).
- Adenoma and adenocarcinoma found in the lungs of the male animals treated at 5% (non sex or dose-related).
- Hyperplastic nodules, hepatocellular carcinoma, hemangioma, and fibrosarcoma observed in the liver of treated animals (low significance)

HISTOPATHOLOGY: NON-NEOPLASTIC
- Non-neoplastic lesions were observed in the subcutis, lungs, kidneys, and liver in the treated groups (non toxicologically significant)

Dose descriptor:

NOAEL

Remarks:

highest dose evaluated

Effect level:

ca. 5 000 - ca. 7 500 mg/kg bw/day (actual dose received)

Sex:

male

Basis for effect level:

other: highest dose evaluated: 5% concentration in diet

Dose descriptor:

NOAEL

Remarks:

highest dose evaluated

Effect level:

ca. 4 000 - ca. 13 000 mg/kg bw/day (actual dose received)

Sex:

female

Basis for effect level:

other: highest dose evaluated: 5% concentration in diet

Critical effects observed:

not specified

Conclusions:

The NOAEL was 5% of the substance in diet, which corresponds to a dose between 5000 and 7500 mg/kg bw/day for male and between 4000 and 13000 mg/kg bw/day in female, and is the highest concentration evaluation during this study.

Executive summary:

Chronic toxicity of the read-across substance silicon dioxide branded as Syloid 244 following an oral exposure was determined according to a method similar to the OECD Guideline for Testing of chemicals 453. Syloid 244 was orally administrated in diet to B6C3F1 mice for 93 weeks at dose levels of 0, 1.25, 2.5, and 5%. Clinical observations were performed routinely throughout the study. Body weight were calculated weekly for the first 55 weeks then biweekly. Food consumption was determined weekly. Haematology and clinical chemistry was performed at termination.

Lungs, bronchus, heart, kidneys, liver, spleen, brain, stomach, colon, intestines, pancreas, adrenal glands, pituitary, thyroid, salivary glands, thymus, testes, prostate, bladder, ovaries, uterus, oviducts, femoral bones, mammary glands, skin, and subcutis were extracted for gross examination. Microscopic examination was performed on liver, kidneys, spleen, heart, and brain.

Animals were sacrificed after 6 and 12 months to obtain additional intermediate data.

No significant or dose-related alterations were observed in food consumption, body and organ weights, haematology, and clinical chemistry and during the histopathology, with the exception of neoplastic tumors found in liver but only of low significance.

The NOAEL was 5% of the substance in diet, which corresponds to a dose between 5000 and 7500 mg/kg bw for male and between 4000 and 13000 mg/kg bw in female, and is the highest concentration evaluation during this study.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

1 700 mg/kg bw/day

Study duration:

chronic

Species:

rat

Repeated dose toxicity: inhalation - systemic effects

Link to relevant study records

Reference

Endpoint:

sub-chronic toxicity: inhalation

Type of information:

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

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study was conducted using a method equivalent to OECD Testing Guideline 413 and meets acceptable scientific standards.

Qualifier:

according to guideline

Guideline:

OECD Guideline 413 (Subchronic Inhalation Toxicity: 90-Day Study)

Deviations:

yes

Remarks:

no ophthalmological examination performed

GLP compliance:

not specified

Limit test:

no

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: TNO Central Institute for the Breeding of Laboratory Animals
- Age at study initiation: 6 weeks
- Weight at study initiation:
- Fasting period before study:
- Housing: singly during exposure period, five males and five females per cage after exposure period
- Diet: ad libitum
- Water: ad libitum

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21°C - 23°C
- Humidity (%): 65% - 75%
- Air changes: 40 m3 per hour

Route of administration:

inhalation: aerosol

Type of inhalation exposure:

whole body

Vehicle:

air

Remarks on MMAD:

MMAD / GSD: Mean primary particle size: 12 nm

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- System of generating particulates/aerosols: Dust feed mechanism + atomizer operated by compressed air

TEST ATMOSPHERE
- Sampling: using a Sartorius SM 13430
- Brief description of analytical method used: gravimetry

Analytical verification of doses or concentrations:

yes

Duration of treatment / exposure:

13 weeks of exposure. Termination at the end of the exposure or 13, 26, 39 or 52 weeks after the end of exposure

Frequency of treatment:

6 hours/day, 5 days/week

Remarks:

Doses / Concentrations:
1, 6, and 30 mg/m3 (Aerosil 200)
Basis:
nominal conc.

No. of animals per sex per dose:

70 males and 70 females per concentration (including control group).

Control animals:

yes, concurrent no treatment

Details on study design:

- Dose selection rationale: a 14-day dose range finding study was performed before the main study. It was found that a concentration of 17 mg/m3 induced slight adverse effects. The concentration of 6 mg/m3 was chosen as it was the German Threshold Limit Value for inert dust such as Aerosil 200. The concentration of 30 mg/m3 was chosen in order to generate adverse effects (but no mortality).

Observations and examinations performed and frequency:

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Daily

BODY WEIGHT: Yes
- Time schedule for examinations: Weekly during exposure, once every 4 weeks during the recovery period.

FOOD CONSUMPTION:
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: No data

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: Yes / No / No data

WATER CONSUMPTION: No data

OPHTHALMOSCOPIC EXAMINATION: No data

HAEMATOLOGY: Yes
- Time schedule for collection of blood: every 13 weeks
- Anaesthetic used for blood collection: No data
- Animals fasted: No data
- How many animals: 10 rats/sex/concentration
- Parameters examined: cell counts, haemoglobin content, packed cell volume, white-cell counts, differential white-cell counts, prothrombin time, and thrombocytes.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: every 13 weeks
- Animals fasted: No data
- How many animals: 10 rats/sex/concentration
- Parameters examined: albumin, alkaline phosphatase, alanine aminotransferase, aspartate aminotransferase, urea, total protein, creatinine, total bilirubin, calcium, potassium, sodium, inorganic phosphate, cholesterol and glucose

URINALYSIS: Yes
- Time schedule for collection of urine: every 13 weeks
- Metabolism cages used for collection of urine: No data
- Animals fasted: No data
- Parameters examined: appearance, volume, density and pH, analysis for protein, occult blood, glucose, ketones, sediment

NEUROBEHAVIOURAL EXAMINATION: No data

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes

Other examinations:

- Collagen content in lungs
- Silicon content in lungs
- Silicon in lymph nodes associated to the lungs

Statistics:

Body weight: analysis of co-variance and Dunnett's multiple comparison test
Organ weight: analysis of variance and Dunnett's multiple comparison test
Haematology: analysis of variance and Dunnett's multiple comparison test
Biochemistryy: analysis of variance and Dunnett's multiple comparison test
Hhistopathological changes: analysis of incidence using the Fisher exact probability test

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 examined

Food efficiency:

not examined

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

not examined

Ophthalmological findings:

not examined

Haematological findings:

effects observed, treatment-related

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

no effects observed

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

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
- Dose-related increase of the respiration rate. The respiration rate returned to normal at the end of exposure.

BODY WEIGHT AND WEIGHT GAIN
- Body weight of male rats exposed to 30mg/m3 was 5% - 10% lower at the end of exposure compared with control group. Body weight returned to normal after 13 weeks post exposure.

HAEMATOLOGY
- Neutrophilic leucocyte count was higher for rats exposed to 30 mg/m3 compared with control group (non-significant). It returned to normal after 13 weeks post exposure.
- Red blood cell count, haemoglobin content, and packed cell volume slightly increased in males exposed to 30 mg Aerosil 200/m3 compared with control group. They returned to normal after 13 weeks post exposure.

CLINICAL CHEMISTRY
- No adverse effects observed compared with control group.

URINALYSIS
- No adverse effects observed compared with control group.

ORGAN WEIGHTS
- Rats exposed to 6 and 30 mg/m3 showed significantly heavier lungs compared with control group, with a greater increase in male rats compared with female rats, and greater increase in rats exposed to 30 mg/m3 compared to rats exposed to 6 mg/m3. It returned to normal after 13 weeks post exposure for rats exposed to 6 mg/m3.

GROSS PATHOLOGY
- Swollen/spongy lungs in rats exposed to the test item. It returned to normal after 26 weeks.

HISTOPATHOLOGY: NON-NEOPLASTIC
- Miscrocopic changes were observed in the lungs compared with the control group at the end of exposure. These changes were dose-related and caused by an inflammatory reaction induced by the test item. Most changes returned to normal during the recovery period.

OTHER FINDINGS
- Lung collagen content: Animals exposed to the test item had higher lung collagen content compared with the control group, with the highest result being obtained for rats exposed to 30 mg/m3 and higher lung collagen content in male rats when compared in female rats. It returned to normal after 52 weeks only for animal exposed to 1 mg/m3.
- Silicon in the lungs and associated lymph nodes: The test item was quickly cleared from the lung and associated lymph nodes.

Dose descriptor:

NOAEC

Remarks:

local

Effect level:

1.3 mg/m³ air (analytical)

Sex:

male/female

Basis for effect level:

other: Mean concentration of the test item of atmosphere when the target concentration was 1 mg/m3

Dose descriptor:

NOAEL

Remarks:

systemic

Effect level:

5.9 mg/L air (analytical)

Sex:

male/female

Basis for effect level:

other: Mean concentration of the test item of atmosphere when the target concentration was 5.9 mg/m3

Critical effects observed:

not specified

Conclusions:

The NOAEL of the substance has been determined to be 1.3 mg/m3 for local effects (on the respiratory tract) and 31 mg/m3 for systemic effects.

Executive summary:

Subchronic toxicity of the read-across substance silicon dioxide branded as Aerosil 200 following an inhalation exposure was determined according to a method similar to the OECD Guideline for Testing of chemicals 413. Wistar rats were exposed to Aerosil 200 as an aerosol 6 hours/day, 5 days/week, for 13 weeks, at dose levels of 0, 1, 6, and 30 mg/m3. Rats were sacrificed at the end of exposure or 13, 26, 39 or 52 weeks after the end of exposure. Clinical observations were performed daily. Body weight were calculated weekly during the exposure then once every 4 weeks during the recovery period. Haematology and clinical chemistry were evaluated, and urinalysis performed once every 13 weeks. Gross pathology and histopathology were performed on sacrificed animals, along with calculation of collagen content in lungs, and silicon content in lungs and associated lymph nodes.

A dose-related increase of the respiration rate was observed in treated animals. Macroscopic and microscopic changes were observed in the lungs are considered to be related to an inflammatory pulmonary reaction, along with the higher neutrophilic leucocyte count seen in rats treated at 30 mg/m3. No effects were identified in the clinical biochemistry and the urinalysis. Red blood cell count, haemoglobin content, and packed cell volume slightly increased in males exposed to 30 mg/m3 of the substance.

Animals exposed to the test item had higher lung collagen content.

During the recovery period, most adverse effects identified in treated animals disappeared and the lungs were cleared from the test.

Systemic effects on haematology parameters were identified at the highest dose of 31 mg/m3. Therefore, the NOAEL has been determined to be 5.9 mg/m3 for systemic effects.

A dose of 1.3 mg/m3 only induced slight local effects that recovered quickly. Therefore, the NOAEL has been determined to be 1.3 mg/m3 for local effects.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEC

31 mg/m³

Study duration:

subchronic

Species:

rat

Repeated dose toxicity: inhalation - local effects

Link to relevant study records

Reference

Endpoint:

sub-chronic toxicity: inhalation

Type of information:

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

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study was conducted using a method equivalent to OECD Testing Guideline 413 and meets acceptable scientific standards.

Qualifier:

according to guideline

Guideline:

OECD Guideline 413 (Subchronic Inhalation Toxicity: 90-Day Study)

Deviations:

yes

Remarks:

no ophthalmological examination performed

GLP compliance:

not specified

Limit test:

no

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: TNO Central Institute for the Breeding of Laboratory Animals
- Age at study initiation: 6 weeks
- Weight at study initiation:
- Fasting period before study:
- Housing: singly during exposure period, five males and five females per cage after exposure period
- Diet: ad libitum
- Water: ad libitum

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21°C - 23°C
- Humidity (%): 65% - 75%
- Air changes: 40 m3 per hour

Route of administration:

inhalation: aerosol

Type of inhalation exposure:

whole body

Vehicle:

air

Remarks on MMAD:

MMAD / GSD: Mean primary particle size: 12 nm

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- System of generating particulates/aerosols: Dust feed mechanism + atomizer operated by compressed air

TEST ATMOSPHERE
- Sampling: using a Sartorius SM 13430
- Brief description of analytical method used: gravimetry

Analytical verification of doses or concentrations:

yes

Duration of treatment / exposure:

13 weeks of exposure. Termination at the end of the exposure or 13, 26, 39 or 52 weeks after the end of exposure

Frequency of treatment:

6 hours/day, 5 days/week

Remarks:

Doses / Concentrations:
1, 6, and 30 mg/m3 (Aerosil 200)
Basis:
nominal conc.

No. of animals per sex per dose:

70 males and 70 females per concentration (including control group).

Control animals:

yes, concurrent no treatment

Details on study design:

- Dose selection rationale: a 14-day dose range finding study was performed before the main study. It was found that a concentration of 17 mg/m3 induced slight adverse effects. The concentration of 6 mg/m3 was chosen as it was the German Threshold Limit Value for inert dust such as Aerosil 200. The concentration of 30 mg/m3 was chosen in order to generate adverse effects (but no mortality).

Observations and examinations performed and frequency:

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Daily

BODY WEIGHT: Yes
- Time schedule for examinations: Weekly during exposure, once every 4 weeks during the recovery period.

FOOD CONSUMPTION:
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: No data

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: Yes / No / No data

WATER CONSUMPTION: No data

OPHTHALMOSCOPIC EXAMINATION: No data

HAEMATOLOGY: Yes
- Time schedule for collection of blood: every 13 weeks
- Anaesthetic used for blood collection: No data
- Animals fasted: No data
- How many animals: 10 rats/sex/concentration
- Parameters examined: cell counts, haemoglobin content, packed cell volume, white-cell counts, differential white-cell counts, prothrombin time, and thrombocytes.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: every 13 weeks
- Animals fasted: No data
- How many animals: 10 rats/sex/concentration
- Parameters examined: albumin, alkaline phosphatase, alanine aminotransferase, aspartate aminotransferase, urea, total protein, creatinine, total bilirubin, calcium, potassium, sodium, inorganic phosphate, cholesterol and glucose

URINALYSIS: Yes
- Time schedule for collection of urine: every 13 weeks
- Metabolism cages used for collection of urine: No data
- Animals fasted: No data
- Parameters examined: appearance, volume, density and pH, analysis for protein, occult blood, glucose, ketones, sediment

NEUROBEHAVIOURAL EXAMINATION: No data

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes

Other examinations:

- Collagen content in lungs
- Silicon content in lungs
- Silicon in lymph nodes associated to the lungs

Statistics:

Body weight: analysis of co-variance and Dunnett's multiple comparison test
Organ weight: analysis of variance and Dunnett's multiple comparison test
Haematology: analysis of variance and Dunnett's multiple comparison test
Biochemistryy: analysis of variance and Dunnett's multiple comparison test
Hhistopathological changes: analysis of incidence using the Fisher exact probability test

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 examined

Food efficiency:

not examined

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

not examined

Ophthalmological findings:

not examined

Haematological findings:

effects observed, treatment-related

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

no effects observed

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

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
- Dose-related increase of the respiration rate. The respiration rate returned to normal at the end of exposure.

BODY WEIGHT AND WEIGHT GAIN
- Body weight of male rats exposed to 30mg/m3 was 5% - 10% lower at the end of exposure compared with control group. Body weight returned to normal after 13 weeks post exposure.

HAEMATOLOGY
- Neutrophilic leucocyte count was higher for rats exposed to 30 mg/m3 compared with control group (non-significant). It returned to normal after 13 weeks post exposure.
- Red blood cell count, haemoglobin content, and packed cell volume slightly increased in males exposed to 30 mg Aerosil 200/m3 compared with control group. They returned to normal after 13 weeks post exposure.

CLINICAL CHEMISTRY
- No adverse effects observed compared with control group.

URINALYSIS
- No adverse effects observed compared with control group.

ORGAN WEIGHTS
- Rats exposed to 6 and 30 mg/m3 showed significantly heavier lungs compared with control group, with a greater increase in male rats compared with female rats, and greater increase in rats exposed to 30 mg/m3 compared to rats exposed to 6 mg/m3. It returned to normal after 13 weeks post exposure for rats exposed to 6 mg/m3.

GROSS PATHOLOGY
- Swollen/spongy lungs in rats exposed to the test item. It returned to normal after 26 weeks.

HISTOPATHOLOGY: NON-NEOPLASTIC
- Miscrocopic changes were observed in the lungs compared with the control group at the end of exposure. These changes were dose-related and caused by an inflammatory reaction induced by the test item. Most changes returned to normal during the recovery period.

OTHER FINDINGS
- Lung collagen content: Animals exposed to the test item had higher lung collagen content compared with the control group, with the highest result being obtained for rats exposed to 30 mg/m3 and higher lung collagen content in male rats when compared in female rats. It returned to normal after 52 weeks only for animal exposed to 1 mg/m3.
- Silicon in the lungs and associated lymph nodes: The test item was quickly cleared from the lung and associated lymph nodes.

Dose descriptor:

NOAEC

Remarks:

local

Effect level:

1.3 mg/m³ air (analytical)

Sex:

male/female

Basis for effect level:

other: Mean concentration of the test item of atmosphere when the target concentration was 1 mg/m3

Dose descriptor:

NOAEL

Remarks:

systemic

Effect level:

5.9 mg/L air (analytical)

Sex:

male/female

Basis for effect level:

other: Mean concentration of the test item of atmosphere when the target concentration was 5.9 mg/m3

Critical effects observed:

not specified

Conclusions:

The NOAEL of the substance has been determined to be 1.3 mg/m3 for local effects (on the respiratory tract) and 31 mg/m3 for systemic effects.

Executive summary:

Subchronic toxicity of the read-across substance silicon dioxide branded as Aerosil 200 following an inhalation exposure was determined according to a method similar to the OECD Guideline for Testing of chemicals 413. Wistar rats were exposed to Aerosil 200 as an aerosol 6 hours/day, 5 days/week, for 13 weeks, at dose levels of 0, 1, 6, and 30 mg/m3. Rats were sacrificed at the end of exposure or 13, 26, 39 or 52 weeks after the end of exposure. Clinical observations were performed daily. Body weight were calculated weekly during the exposure then once every 4 weeks during the recovery period. Haematology and clinical chemistry were evaluated, and urinalysis performed once every 13 weeks. Gross pathology and histopathology were performed on sacrificed animals, along with calculation of collagen content in lungs, and silicon content in lungs and associated lymph nodes.

A dose-related increase of the respiration rate was observed in treated animals. Macroscopic and microscopic changes were observed in the lungs are considered to be related to an inflammatory pulmonary reaction, along with the higher neutrophilic leucocyte count seen in rats treated at 30 mg/m3. No effects were identified in the clinical biochemistry and the urinalysis. Red blood cell count, haemoglobin content, and packed cell volume slightly increased in males exposed to 30 mg/m3 of the substance.

Animals exposed to the test item had higher lung collagen content.

During the recovery period, most adverse effects identified in treated animals disappeared and the lungs were cleared from the test.

Systemic effects on haematology parameters were identified at the highest dose of 31 mg/m3. Therefore, the NOAEL has been determined to be 5.9 mg/m3 for systemic effects.

A dose of 1.3 mg/m3 only induced slight local effects that recovered quickly. Therefore, the NOAEL has been determined to be 1.3 mg/m3 for local effects.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEC

1.3 mg/m³

Study duration:

subchronic

Species:

rat

Repeated dose toxicity: dermal - systemic effects

Link to relevant study records

Reference

Reference 1

Endpoint:

short-term repeated dose toxicity: dermal

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Justification for type of information:

In accordance with Annex VIII of REACH, Column 2, assessing the short-term repeated dose toxicity by the dermal route is relevant only if the inhalation of the substance is unlikely, which is not the case for the registered substance as the substance is a solid generating dust when handle. Moreover due to the particle size of the substance, it cannot be absorbed as such following a dermal exposure. It must first be dissolved for the absorption process to occur. However, the high lattice energy of the structure implies that it would require conditions far more extreme than those the substance will experience on the skin. Therefore no dissolution is expected following a dermal exposure, and no absorption will occur.

Critical effects observed:

not specified

Reference 2

Endpoint:

sub-chronic toxicity: dermal

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Justification for type of information:

In accordance with Annex IX of REACH, Column 2, assessing the subchronic repeated dose toxicity by the dermal route is relevant only if the physicochemical properties of the substance suggest a significant rate of absorption through the skin. Due to the particle size of the substance, it cannot be absorbed as such following a dermal exposure. It must first be dissolved for the absorption process to occur. However, the high lattice energy of the structure implies that it would require conditions far more extreme than those the substance will experience on the skin. Therefore no dissolution is expected following a dermal exposure, and no absorption will occur.

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - local effects

Link to relevant study records

Reference

Reference 1

Endpoint:

short-term repeated dose toxicity: dermal

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Justification for type of information:

In accordance with Annex VIII of REACH, Column 2, assessing the short-term repeated dose toxicity by the dermal route is relevant only if the inhalation of the substance is unlikely, which is not the case for the registered substance as the substance is a solid generating dust when handle. Moreover due to the particle size of the substance, it cannot be absorbed as such following a dermal exposure. It must first be dissolved for the absorption process to occur. However, the high lattice energy of the structure implies that it would require conditions far more extreme than those the substance will experience on the skin. Therefore no dissolution is expected following a dermal exposure, and no absorption will occur.

Critical effects observed:

not specified

Reference 2

Endpoint:

sub-chronic toxicity: dermal

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Justification for type of information:

In accordance with Annex IX of REACH, Column 2, assessing the subchronic repeated dose toxicity by the dermal route is relevant only if the physicochemical properties of the substance suggest a significant rate of absorption through the skin. Due to the particle size of the substance, it cannot be absorbed as such following a dermal exposure. It must first be dissolved for the absorption process to occur. However, the high lattice energy of the structure implies that it would require conditions far more extreme than those the substance will experience on the skin. Therefore no dissolution is expected following a dermal exposure, and no absorption will occur.

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Chronic toxicity of the read-across substance silicon dioxide, a synthetic amorphous silica (SAS), branded as Syloid 244 following an oral exposure was determined according to a method similar to the OECD Guideline for Testing of chemicals 453. Syloid 244 was orally administrated in diet to Fisher rats - which is the preferred species for this study - for 103 weeks and to mice for 93 weeks, at dose levels of 0, 1.25, 2.5, and 5%.

Clinical observations were performed routinely throughout the study. Body weight were calculated weekly for the first 55 weeks of the study then biweekly. Food consumption was determined weekly. Haematology and clinical chemistry was performed at termination.

Lungs, bronchus, heart, kidneys, liver, spleen, brain, stomach, colon, intestines, pancreas, adrenal glands, pituitary, thyroid, salivary glands, thymus, testes, prostate, bladder, ovaries, uterus, oviducts, femoral bones, mammary glands, skin, and subcutis were extracted for gross examination. Microscopic examination was performed on liver, kidneys, spleen, heart, and brain.

Animals were sacrificed after 6 and 12 months to obtain additional intermediate data.

No significant or dose-related alterations were observed in food consumption, body and organ weights, haematology, clinical chemistry, and during the histopathology.

The NOAEL was 5% of the substance in diet, which corresponds to a dose between 1700 and 3000 mg/kg bw/day for both male and female rats, between 5000 and 7500 mg/kg bw/day for male mice, and between 4000 and 13000 mg/kg bw/day for female mice, and is the highest concentration evaluation during this study. As it is the lowest actual dose received and it was obtained on rats, which is the preferred species for this study, the NOAEL for repeated dose toxicity by oral route has been determined to be 1700 mg/kg bw/day.

Subchronic toxicity of the read-across substance silicon dioxide, a SAS, branded as Aerosil 200 following an inhalation exposure was determined according to a method similar to the OECD Guideline for Testing of chemicals 413. Wistar rats were exposed to Aerosil 200 as an aerosol 6 hours/day, 5 days/week, for 13 weeks, at dose levels of 0, 1, 6, and 30 mg/m3. Rats were sacrificed at the end of exposure or 13, 26, 39 or 52 weeks after the end of exposure. Clinical observations were performed daily. Body weight were calculated weekly during the exposure then once every 4 weeks during the recovery period. Haematology and clinical chemistry were evaluated, and urinalysis performed once every 13 weeks. Gross pathology and histopathology were performed on sacrificed animals, along with calculation of collagen content in lungs, and silicon content in lungs and associated lymph nodes.

A dose-related increase of the respiration rate was observed in treated animals. Macroscopic and microscopic changes were observed in the lungs are considered to be related to an inflammatory pulmonary reaction, along with the higher neutrophilic leucocyte count seen in rats treated at 30 mg/m3. No effects were identified in the clinical biochemistry and the urinalysis. Red blood cell count, haemoglobin content, and packed cell volume slightly increased in males exposed to 30 mg/m3 of the substance.

Animals exposed to the test item had higher lung collagen content.

During the recovery period, most adverse effects identified in treated animals disappeared and the lungs were cleared from the test.

The only systemic effects identified were reversible modifications of some haematology parameters at the highest dose that are not considered as adverse effect. Therefore, the NOAEL has been determined to be 31 mg/m3 for systemic effects.

A dose of 1.3 mg/m3 only induced slight local effects that recovered quickly. Therefore, the NOAEL has been determined to be 1.3 mg/m3 for local effects.

Justification for selection of repeated dose toxicity via oral route - systemic effects endpoint:

The study was performed on a read-across substance according to a method similar to OECD Testing Guideline 453 on rats, which is the recommended species for this study.

Justification for selection of repeated dose toxicity inhalation - systemic effects endpoint:

The study was performed on a read-across substance according to a method similar to OECD Testing Guideline 413 on rats, which is the recommended species for this study.

Justification for selection of repeated dose toxicity inhalation - local effects endpoint:

The study was performed on a read-across substance according to a method similar to OECD Testing Guideline 413 on rats, which is the recommended species for this study.

Justification for selection of repeated dose toxicity dermal - systemic effects endpoint:

In accordance with Annex VIII of REACH, Column 2, assessing the Repeated-Dose Toxicity by dermal route is relevant only if the inhalation of the substance is unlikely, which is not the case for the registered substance as the substance is a solid generating dust when handle.

Justification for selection of repeated dose toxicity dermal - local effects endpoint:

In accordance with Annex VIII of REACH, Column 2, assessing the Repeated-Dose Toxicity by dermal route is relevant only if the inhalation of the substance is unlikely, which is not the case for the registered substance as the substance is a solid generating dust when handle.

Justification for classification or non-classification

Repeated-dose toxicity studies by oral route and inhalation has been performed on a group of branded silicon dioxide substances defined as synthetic amorphous silica (SAS), selected as a read-across substances for the registered substance as they represent the worst-case scenario.

The registered substance and SAS are synthetic silicate compounds with similar composition and physical, chemical, and toxicological properties with no lipophilic character. Considering the substances are practically insoluble, have no vapour pressure, are particulates, and are not expected to release their constituents under normal physiological conditions, it is unlikely that they would be bioavailable to cause generalised systemic effects. Therefore, the results obtained on the SAS Syloid 244 may be used to perform a read-across to the registered substance for repeated-dose toxicity by oral route.

Capacity of synthetic inorganic silicon compounds to induce adverse effects following a repeated exposure by inhalation are considered to be driven by particle shape and particle size, more than chemical composition and structure, as it will determine their capacity to induce inflammation and the reversibility of the process (OECD, 2004). The registered substance and Aerosil 200 have a similar particle shape. Regarding the particle size, the primary particle size of the SAS Aerosil 200 tested during the study used for the purpose of the read-across, was calculated to theoretically have a range between 6 and 45 nm (Reuzel, 1991). However, it is important to note that primary particles do not exist as individual free units, but only as aggregates and agglomerates. Because of technical problems, the aerodynamic aggregate/agglomerate size distribution in the test atmospheres was not determined. The approximate maximum of the geometric aggregate/agglomerate size distribution of SAS Aerosil 200 was estimated to be at 10 µm (OECD, 2004). The registered substance has a mean particle size of 18 µm, and its particles are therefore bigger than Aerosil 200. This implies that SAS Aerosil 200 will be more inhalable than the registered substance and that its particles will reach lower part of the respiratory tract. Therefore, the results obtained on SAS Aerosil 200 are considered as conservative in order to perform a read-across to the registered substance for repeated-dose toxicity by inhalation.

Considering that SAS is not meeting the criteria for classification according to Regulation (EC) No.1272/2008 on the Classification, Labelling and Packaging of Substances and Mixtures, and that it represents a worst-case scenario, the registered substance is not be classified according to Regulation (EC) No.1272/2008 on the Classification, Labelling and Packaging of Substances and Mixtures.

OECD SIDS (2004) Synthetic Amorphous Silica and Silicates

Reuzel, P.G.J. et al. (1991) Subchronic inhalation toxicity of amorphous silicas and quartz dust in rats. Fd Chem Toxic 29: 341-356