Silica, amorphous

Agent Name
Silica, amorphous
CAS Number
61790-53-2; 112926-00-8; 69012-64-2; 60676-86-0
Formula
O2-Si
Major Category
Mineral Dusts
Synonyms
Diatomaceous earth, containing < 1% crystalline silica; Diatomaceous silica; Diatomite; Precipitated amorphous silica; Silica gel; Silicon dioxide (amorphous); [NIOSH]
Category
Other Mineral Dusts
Description
Transparent to gray, odorless powder. [Note: Amorphous silica is the non-crystalline form of SiO2.]; [NIOSH]
Sources/Uses
Used as a filler in rubber products, paints, animal feeds, pesticides, insulation materials, and cosmetics; [Rom, p. 527] Silica nanoparticle applications include leukemia cell biomarkers, cancer therapy, drug delivery, mechanical polishing, and additives to drugs, cosmetics, printing inks, varnishes, and food; [PMID 21191487] Polycrystalline silicon and silicon dioxide materials are etched in semiconductor manufacturing. [CSH, p. 45]
Comments
Silica, amorphous (7631-86-9) is "not classifiable as to carcinogenicity to humans." [IARC] Documentation and TLV withdrawn in 2006 because of insufficient data; [ACGIH] The main problem in assessing the risk of exposure to diatomaceous earth is its varying degree of contamination with crystalline silica. While the natural version usually contains about 1%, up to 60% may be present in flux-calcined amorphous silica. [Rom, p. 527]
Biomedical References

Exposure Assessment

Bioaccumulates
Yes
PEL (OSHA)
20 mppcf(diatomaceous earth uncalcined, precipitated silica and silica gel), 30 mg/m3/%SiO2+2, total dust, 10 mg/m3/%SiO2+2, respir. dust(silica fused)
MAK
0.5 mg/m3, inhal. fraction(diatomaceous earth uncalcined), 0.3 mg/m3, respir. fraction(diatomaceous earth calcined, silica fume, and fused)
IDLH (NIOSH)
3000 mg/m3

Adverse Effects

Fibrogenic
Yes
IARC Carcinogen
Not classifiable

Diseases, Processes, and Activities Linked to This Agent

Diseases

Occupational diseases associated with exposure to this agent:

Processes

Industrial Processes with risk of exposure: