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 [IARC] Documentation and TLV withdrawn in 2006 because of insufficient data; [ACGIH] The main problem in assessing the risk of exposure to diatomaceous earth is its varying degree of contamination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

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

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

IDLH (NIOSH)

3000 mg/m3

Adverse Effects
Fibrogenic

Yes

IARC Carcinogen

Not Classifiable

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