Ashes (residues), rice husk

Acute Toxicity: inhalation

Administrative data

Endpoint:

acute toxicity: inhalation

Type of information:

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

Adequacy of study:

supporting study

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

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 403 (Acute Inhalation Toxicity)

GLP compliance:

not specified

Remarks:

GLP study according to the authors. No further details on testing laboratory given.

Test type:

standard acute method

Limit test:

yes

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: Central Institute for Breeding of Laboratory Animals, TNO, Zeist, The Netherlands
- Weight at study initiation: 182 g (males), 141 g (females)
- Housing: groups of five animals to a cage
- Diet (e.g. ad libitum): stock diet for rats (TNO) ad libitum
- Water (e.g. ad libitum): tap water ad libitum


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21 +/- 1
- Humidity (%): 50-60

Administration / exposure

Route of administration:

inhalation: aerosol

Type of inhalation exposure:

whole body

Vehicle:

other: unchanged (no vehicle)

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: stainless steel exposure chamber
- Exposure chamber volume: 1.5 m³
- Rate of air: 0.97 m³/h
- System of generating particulates/aerosols: The test material, a fluffy powder, was continuously dispersed in air by means of a brush-type dosing apparatus (Buerstendosierer Type III/A) with the maximum attainable concentration of the test material in the atmosphere.
- Method of particle size determination: Particle size determination was carried out in a sample taken from the test atmosphere in the chamber using a cascade impactor. The Netherlands Energy Research Foundation has determined a volume diameter of fumed hydrophobic silica aggregates in ethanol by means of a light scattering method (Swithenbank and Taylor, 1979. Size distribution measurement for near-monodisperse particles and sprays, Department of Chemical Engineering and Fuel Technology, University of Sheffield, England. Report No. HIC 315). Fromthe volume mean diemater (VMD) the mass median diameter can be calculated by multiplying the VMD by the density.


TEST ATMOSPHERE (if not tabulated)
- Particle size distribution: The results of the particle size distribution determination in a sample of the aerosol showed that the aerodynamic diameter of about 56% of the particles was smaller than 5 µm
- MMAD (Mass median aerodynamic diameter): 2.9 µm

Analytical verification of test atmosphere concentrations:

yes

Remarks:

The actual concentration was determined gravimetrically by passing a measured quantity of the test atmosphere through a glass fiber filter (Type SM 13400, Sartorius). Samples were taken at 60, 130, and 170 min after starting the exposure.

Duration of exposure:

4 h

Concentrations:

477 mg/m³

No. of animals per sex per dose:

5

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: rats were examined for clinical signs daily. Body weights were recorded prior to exposure and at Days 1, 2, 4, 7, and 14.
- Necropsy of survivors performed: yes

Results and discussion

Effect levels

Sex:

male/female

Dose descriptor:

LC50

Effect level:

> 0.477 mg/L air (analytical)

Exp. duration:

4 h

Mortality:

No mortality occurred during the exposure period or during the subsequent observation period of 14 days.

Clinical signs:

other: During the 4-h exposure period with the maximum attainable concentration of test material in air (477 mg/m³) the rats were somewhat restless and drooping eyelids were observed.

Body weight:

The body weight decreased during the first 2 days and increased in a normal way thereafter.

Gross pathology:

At autopsy no abnormalities were found in gross pathology.

Applicant's summary and conclusion

Interpretation of results:

not classified

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

The results of the acute inhalation toxicity study indicate that fumed hydrophobic amorphous silica is virtually acutely nontoxic at the maximum attainable aerosol concentration.