Silica, amorphous

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 [IARC] Documentation and TLV withdrawn in 2006 because of insufficient data; [ACGIH] The main problem in assessing the risk of exposure to diatomaceous earth is its varying degree of contamination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

Yes

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)

0.3 mg/m3, respir. fraction (diatomaceous earth calcined, silica fume, and fused)

3000 mg/m3

Yes

Not classifiable

Diseases

Occupational diseases associated with exposure to this agent:

• Pneumoconioses, other

Processes

Industrial Processes with risk of exposure:

• Cement Producing
• Farming (Feed Additives)
• Mining
• Semiconductor Manufacturing