NIOSH
HAZARD REVIEW
Health
Effects of Occupational Exposure
to
Respirable Crystalline Silica
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Table
A–1. U.S. guidelines and limits for occupational exposure to
crystalline silica
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Reference
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Substance
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Guideline
or limit (mg/m3)
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| NIOSH [1974] | Crystalline silica:* quartz, cristobalite, and tridymite as respirable dust | REL† = 0.05 (for up to a 10-hr workday during a 40-hr workweek) |
| OSHA
[29 CFR 1910.1000–Table Z-3] |
Respirable
crystalline silica, quartz Respirable crystalline silica, cristobalite Respirable crystalline silica, tridymite |
PEL
= 10 ÷ % quartz + 2 (8-hr TWA) PEL = half of the value calculated from the formula for quartz PEL = half of the value calculated from the formula for quartz |
| MSHA [30 CFR 56, 57, 70, 71] | Respirable
quartz in underground and surface metal and nonmetal mines Respirable crystalline silica present in concentrations >5% in surface and underground coal mines |
PEL
= 10 ÷ % quartz + 2 (8-hr TWA) RDS† = 10 ÷ % quartz (8-hr TWA) |
| ACGIH [2001] | Respirable
crystalline silica, quartz Respirable crystalline silica, cristobalite Respirable crystalline silica, tridymite |
TLV = 0.05 (8-hr TWA) TLV = 0.05 (8-hr TWA) TLV = 0.05 (8-hr TWA) |
| Adapted
from Hearl [1996]. * Identified by NIOSH as a potential occupational carcinogen [54 Fed Reg. 2521 (1989)]. † Abbreviations: REL = recommended exposure limit; PEL = permissible exposure limit; RDS = respirable dust standard; TLV = threshold limit value; TWA = time-weighted average. |
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