SILICA, CRYSTALLINE, MIXED RESPIRABLE (QUARTZ, CRISTOBALITE, TRIDYMITE) | Occupational Safety and Health Administration

Chemical Identification
CAS #	14808-60-7 (quartz), 14464-46-1 (cristobalite), 15468-32-3 (tridymite)
Formula	Mixed
Synonyms	silica; crystalline silica; quartz; quartz dust; critobalite; cristobalite dust; tripoli

Physical Properties
Physical description	Colorless, odorless solid.
Boiling point	4046°F	Molecular weight	60.1
Freezing point/melting point	3110°F	Vapor pressure	0 mmHg (approx)
Flash point		Vapor density
Specific gravity	2.66	Ionization potential
Lower explosive limit (LEL)		Upper explosive limit (UEL)
NFPA health rating		NFPA fire rating
NFPA reactivity rating		NFPA special instruction
Vapor hazard ratio (VHR)
Historical exceedance percentage
Target organs

Monitoring Methods Used by OSHA
Analyte code (IMIS no.)	9000
Sampling group
Sampler/Sampling media	Tared low-ash 37 mm PVC filter, 5 microns, preceded by 10 mm nylon Dorr-Oliver cyclone for respirable samples. [SLTC108]
Sampling time^*	240-480 min
Sampling volume (TWA)^*	816 L
Sampling flow rate (TWA)^*	1.7 L/min ±0.2 L/min
Sampling volume (STEL/Peak/C)^*	408-816 L
Sampling flow rate (STEL/Peak/C)^*	1.7 L/min ±0.2 L/min
Analytical method instruments	XRD
Method reference	OSHA ID-142 (fully validated)
Notes	OSHA personnel must obtain pre-weighted filters from SLTC. Quartz and cristobalite analysis may be submitted on the same filter. If a bulk sample is taken, send it to the lab in a separate mailing container from associated air samples. Bulk sampling is optional. In cases where bulk samples are submitted high-volume filter samples (without cyclones, preferably >1 g), and representative settled dust are preferred. Request analysis for Silica, Crystalline, Mixed Respirable (Quartz, Cristobalite, Tridymite), IMIS Code 9000. Cristobalite is a polymorph of respirable crystalline silica that occurs in workplaces where silica is heated to extremely hot temperatures (>1460 °C). If it is suspected that cristobalite may be present, note this on the Form OSHA-91A. Cristobalite is rare and will usually only be analyzed if the reason to suspect its presence is noted on the Form 91A. Tridymite, which is even rarer, will not be analyzed by SLTC because a standard reference material is not readily available.
Special requirements	The 10-mm nylon Dorr-Oliver operated at an optimized flow rate of 1.7 L/min is capable of collecting a sufficient quantity of quartz to exceed the limit of quantification when airborne concentrations are at or above the action level, provided that at least 4-hour air samples are taken.

Bulk/Wipe Method
Wipe Sampler/Sampling media
Bulk Method

On-Site Screening Techniques
Device
Model/Type
Sampling information (see manufacturer instructions)

**Exposure Limits**
OSHA PEL 8-hour TWA (ST) STEL (C) Ceiling Peak		NIOSH REL Up to 10-hour TWA (ST) STEL (C) Ceiling		ACGIH TLV© 8-hour TWA (ST) STEL (C) Ceiling		CAL/OSHA PEL 8-hour TWA (ST) STEL (C) Ceiling Peak
PEL-TWA	50 µg/m³ [25 µg/m³ Action Level]	REL-TWA	0.05 mg/m³	TLV-TWA	0.025 mg/m³ (respirable particulate matter), [2009]	PEL-TWA	0.05 mg/m³
PEL-STEL		REL-STEL		TLV-STEL		PEL-STEL
PEL-C		REL-C		TLV-C		PEL-C
Skin notation	N	Skin notation	N	Skin notation	N	Skin notation	N
Notes: See 29 CFR 1910.1053, Respirable crystalline silica. See 29 CFR 1910.1000 Table Z-3, Mineral Dusts for any operations or sectors where the exposure limits in 1910.1053 are stayed or otherwise not in effect.		Notes: CARCINOGEN (Ca): RESPIRABLE FRACTION, REDUCE EXPOSURE TO LOWEST FEASIBLE CONCENTRATION. See Appendix A, NIOSH Potential Occupational Carcinogens.		Notes: See Appendix C: Particle Size-Selective Sampling Criteria for Airbone Particulate Matter		Notes: See footnote (n). See also California Code of Regulations, Title 8 §5204. Occupational Exposures to Respirable Crystalline Silica, and §2532.3. Occupational Exposures to Crystalline Silica.
Health factors: See NIH-NLM PubChem.		IDLH	50 mg/m³
Carcinogenic classifications: IARC-1, NIOSH-Ca, NTP-K, TLV-A2, MAK-1		Notes: Ca
AIHA emergency response planning guidelines - ERPG-1/ERPG-2/ERPG-3:

Additional Resources and Literature References

NOAA: CAMEO Chemicals -

NIOSH: Pocket Guide to Chemical Hazards - Silica, crystalline (as respirable dust)

Literature References

ACGIH: Documentation of the Threshold Limit Values (TLVs) and Biological Exposure Indices (BEIs) - Silica, Crystalline - Alpha quartz [1317-95-9; 14808-60-7] and cristobalite [14464-46-1]. See annual publication for most recent information.
American Thoracic Society: Adverse effects of crystalline silica exposure. Am J Respir Crit Care Med. 155:761-768, 1997.
IARC: IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Volume 68, Silica. 1997.
IARC: IARC Monographs: Arsenic, Metals, Fibres, and Dusts, A Review of Human Carcinogens, Volume 100 C. 2012.
IARC: Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Man. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work). Available at: http://monographs.iarc.fr/index.php p. V68, 183, 1997.
NIOSH: Criteria for a Recommended Standard - Occupational Exposure to Crystalline Silica. 1974.
NIOSH: Occupational Health Guideline for Crystalline Silica. 1978.
Parks, C.G., Conrad, K., Cooper, G.S.: Occupational exposure to crystalline silica and autoimmune disease. Environ Health Perspect. 107 Suppl 5:793-802, Oct 1999.
Steenland, K.; Attfield, M.; Mannejte, A. Pooled Analyses of Renal Disease Mortality and Crystalline Silica Exposure in Three Cohorts. Ann. Occup. Hyg. 2002, 46, 4-9.

SILICA, CRYSTALLINE, MIXED RESPIRABLE (QUARTZ, CRISTOBALITE, TRIDYMITE)‡

Chemical Identification

Physical Properties

Monitoring Methods Used by OSHA

Bulk/Wipe Method

On-Site Screening Techniques

Exposure Limits

Additional Resources and Literature References