Mica

Synonyms

Biotite; Lepidolite; Margarite; Muscovite; Phlogopite; Roscoelite; Zimmwaldite; [NIOSH] Mica, respirable dusts;

Category

Other Mineral Dusts

Description

Colorless, odorless flakes or sheets of hydrous silicates; [NIOSH] Crystalline silica not bound to other minerals is "free" silica. Silicates are minerals in which silicon and oxygen are combined with other elements. [Rom, p. 364]

Sources/Uses

Mica, mainly muscovite and phlogopite, contains less than 1% quartz. Other species of mica are biotite, lepidolite, zimmwaldite, and roscoelite. Used as a filler for paint, cement, asphalt, and insulation material for electrical cables; Also used in drilling muds, cosmetics, and vacuum tubes/condensers; [ACGIH] Sericite is a variety of white mica; it is similar to muscovite and is used as a filler, carrier, and lubricant; [Reference #1]

Comments

"However, information is sufficient to establish that mica pneumoconiosis is most commonly seen in individuals who have had 10-20 years of exposure to mica, after a latency period of several decades. . . . In one study which examined the relationship between mica concentration, duration of exposure, and onset of disease, it was reported that no cases were observed among workers exposed to mica dusts at concentrations of 1.8 mg/m3 or less, irrespective of exposure duration." [ACGIH] A mixed-dust pneumoconiosis reported in mica miners appears to be related to free silica contamination of ores. [Rosenstock, p. 412] The existence of a mica pneumoconiosis is controversial and is based on a few case reports. [Hendrick, p. 170] Three cases of pneumoconiosis were diagnosed among sericite plant workers in Parana, Brazil. 44 workers with an average 13.5 years of exposure were examined. 52% of workers had chest x-ray opacities, and 18% had reduced FEV1 on pulmonary function testing. [Reference #1] "Occupational exposure to mica dust is responsible for diffuse infiltrative lung disease by overload processes." [Reference #2]

Reference Link #1

Biomedical References

Insufficient data

Yes

0.1 mg/m3, respirable fraction

20 mppcf, < 1% crystalline silica

1500 mg/m3

Excerpts from Documentation for IDLHs

Basis for revised IDLH: The available toxicological data contain no evidence that an acute exposure to a high concentration of mica would impede escape or cause any irreversible health effects within 30 minutes.

Reference Link #2

Yes

Diseases

Occupational diseases associated with exposure to this agent:

• Pneumoconioses, other

Processes

Industrial Processes with risk of exposure:

• Mining
• Petroleum Production and Refining