Fumes, silica

Acute Toxicity: inhalation

Administrative data

Endpoint:

acute toxicity: inhalation

Type of information:

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

Adequacy of study:

weight of evidence

Justification for type of information:

No toxicological data were available for silica fume and, therefore, a read-across approach was used. The dissolution, composition and surface properties were the most important parameters considered when deciding which substances can be used for read-across.

Based on the composition, surface characteristics, and bioaccessibility data, silica fume was assumed to have toxicological properties similar to those of sparingly synthetic amorphous silicas. Therefore read-across was carried out using available toxicological studies with synthetic amorphous silica (SAS).

Details on the read-across approach are presented in Iuclid section 13.

Cross-reference

Reason / purpose for cross-reference:

read-across source

Reference

Endpoint:

acute toxicity: inhalation

Type of information:

other: A scientific review by an authorative international body

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Reason / purpose for cross-reference:

reference to same study

Principles of method if other than guideline:

OECD evaluated the available test data on synthetic amorphous silica.

GLP compliance:

no

Remarks:

'yes' status in critical studies

Test type:

other: different acute inhalation toxicity tests

Species:

rat

Sex:

male/female

Dose descriptor:

LC0

Effect level:

> 0.139 mg/L air

Exp. duration:

4 h

Remarks on result:

other: hydrophilic pyrogenic silica

Sex:

male/female

Dose descriptor:

LC0

Effect level:

> 0.691 mg/L air

Exp. duration:

4 h

Remarks on result:

other: hydrophilic precipitated silica

Sex:

male/female

Dose descriptor:

LC50

Effect level:

> 2.08 mg/L air

Exp. duration:

4 h

Remarks on result:

other: hydrophilic pyrogenic silica

All acute inhalation studies performed with dry dust were hampered by the technical problem to achieve the recommended highest test concentration of 5 mg/l, apparently attributable to the high adhesive forces which caused rapid precipitation onto equipment walls. Therefore, the maximum attainable chamber concentrations were distinctly lower than envisaged.

Interpretation of results:

practically nontoxic

Remarks:

Migrated information Criteria used for interpretation of results: OECD GHS

Conclusions:

OECD (2004) includes seven acute inhalation toxicity studies with synthetic amorphous silica, of which three are regarded as critical studies for SIDS endpoint. These three studies are conducted with hydrophilic pyrogenic or precipitated silica. In a study where LC50 >2.08 mg/L was suggested, none of the animals died. The SAS dusts are considered as acutely non-toxic.

Executive summary:

The OECD (2004) reviewed that there was no lethal effects following inhalation exposure of rats to the highest technically feasible concentrations of 140 to 2,000 mg/m³ of hydrophilic precipitated or pyrogenic silica. However, the acute inhalation of synthetic amorphous silica dust may cause discomfort and stress as well as signs of local irritation to the nasal, bronchiolar and ocular mucous membranes. In conclusion, the synthetic amorphous silica dust is considered to be acutely non-toxic via an inhalation route.

Materials and methods

Test material

Test material information

Constituent 1

Reference substance name:

Fumes, silica

EC Number:

273-761-1

EC Name:

Fumes, silica

Cas Number:

69012-64-2

Molecular formula:

SiO2

IUPAC Name:

silanedione

Details on test material:

- Name of test material (as cited in study report): high grade silica fume; low grade silica fume
- Analytical purity: high grade: SiO2 96.4% (w/w); low grade: SiO2 83.8% (w/w)

Results and discussion

Effect levels

Dose descriptor:

LC50

Effect level:

> 2.08 mg/L air

Applicant's summary and conclusion

Interpretation of results:

GHS criteria not met

Conclusions:

The OECD (2004) reviewed that there was no lethal effects following inhalation exposure of rats to the highest technically feasible concentrations of 140 to 2,000 mg/m3 of hydrophilic precipitated or pyrogenic silica.