OSHA comments from the January 19, 1989 Final Rule on Air Contaminants Project extracted from 54FR2332 et. seq. This rule was remanded by the U.S. Circuit Court of Appeals and the limits are not currently in force.

CAS: None; Chemical Formula: None

OSHA formerly regulated perlite under its generic total particulate limit of 15 mg/m3. The ACGIH has a TLV-TWA of 10 mg/m3 for perlite as total dust containing less than 1 percent quartz. The proposed PELs were 10 mg/m3 (total particulate) and 5 mg/m3 TWA (respirable particulate): however, the final rule retains the 15-mg/m3 TWA PEL for perlite as total particulate containing less than 1 percent quartz. The respirable fraction limit of 5 mg/m3 is also retained. Perlite is a natural volcanic glass; it is essentially an amorphous mineral consisting of fused sodium-potassium-aluminum silicate.

Perlite is reported to have a free-silica content varying from zero to 3 percent (Anderson, Selvig, Baur et al. 1956 and the Perlite Institute, both as cited in ACGIH 1986/Ex. 1-3, p. 467). In its processed crude and expanded forms, perlite is reported to have a measurable quartz content of 0.4 percent quartz and 0.2 percent cristobalite (Sheckler 1977, as cited in ACGIH 1986/Ex. 1-3, p. 467). There are no published reports of adverse physiologic effects from exposure to perlite dust. NIOSH, the only commenter on perlite, has not reviewed the evidence for this substance in depth (Ex. 8-47, Table N4).

OSHA finds that perlite is nontoxic when airborne total particulate concentrations are maintained at levels of 15 mg/m3 or below and when its quartz content is limited to a level below 1 percent crystalline silica. For these reasons, the final rule establishes an 8-hour PEL of 15 mg/m3 TWA for total perlite dust containing less than 1 percent quartz and retains the 5-mg/m3 TWA PEL for the respirable fraction of perlite dust. OSHA concludes that these limits protect workers from the significant risk of eye, skin, and other forms of physical irritation.

Page last reviewed: September 28, 2011