Skip directly to site content Skip directly to page options Skip directly to A-Z link


Centers for Disease Control and Prevention. CDC twenty four seven. Saving Lives, Protecting People
															Search
		×
			NIOSH
			NIOSH
				All CDC
				Submit
			For a full list of topics:A-Z Index
			Advanced Search
		Advanced Search


The National Institute for Occupational Safety and Health (NIOSH)


Facebook
        Twitter
        LinkedIn
        Syndicate





Silica, crystalline (as respirable dust)										Related Pages
										May 1994
Immediately Dangerous to Life or Health Concentrations (IDLH)
**CAS number:** 14808–60–7
**NIOSH REL:** 0.05 mg/m3 TWA; NIOSH considers crystalline silica to be a potential occupational carcinogen as defined by the OSHA carcinogen policy [29 CFR 1990].
**Current OSHA PEL:**TWA 50 μg/m3
**1989 OSHA PEL:** Cristobalite: 0.05 mg/m3 TWA
Tridymite: 0.05 mg/m3 TWA
Quartz: 0.1 mg/m3 TWA
Tripoli: 0.1 mg/m3 TWA
**1993-1994 ACGIH TLV:** Quartz (respirable dust): 0.1 mg/m3 TWA
Cristobalite (respirable dust): 0.05 mg/m3 TWA
Tridymite (respirable dust): 0.05 mg/m3 TWA
**Description of substance:** Varies
**Original (SCP) IDLH*:** No Evidence [*Note: “Effective” IDLH = 500 times the OSHA PEL — see discussion below.]
**Basis for original (SCP) IDLH:** The available toxicological data show no evidence that indicates an acute exposure to a high concentration of crystalline silica would impede escape or cause any irreversible health effects within 30 minutes. For this draft technical standard, therefore, respirators have been selected on the basis of the assigned protection factor afforded by each device. However, for some particulate substances for which no evidence of an IDLH exists, the determination of allowable respiratory protection based on protection factors may result in the assignment of respirators for concentrations that are not likely to be encountered in the occupational environment. Therefore, for all such particulate substances it has been arbitrarily determined that only the “most protective” respirators are permitted for use in concentrations exceeding 500  ́ the OSHA PEL.
**Short-term exposure guidelines:** None developed
**ACUTE TOXICITY DATA:**
**Animal or human data:** None relevant for use in determining the revised IDLH.

**Revised IDLH:** 25 mg/m3 (Cristobalite & Tridymite); 50 mg/m3 (Quartz & Tripoli)**Basis for revised IDLH:** The available toxicological data contain no evidence that an acute exposure to a high concentration of crystalline silica would impede escape or cause any irreversible health effects within 30 minutes. However, the revised IDLHs for crystalline silica are 25 mg/m3 for Cristobalite and Tridymite and 50 mg/m3 for Quartz and Tripoli, based on being 500 times the 1989 OSHA PELs of 0.05 mg/m3 and 0.1 mg/m3, respectively (500 is an assigned protection factor for respirators and was used arbitrarily during the Standards Completion Program for deciding when the “most protective” respirators should be used for particulates). [Note: NIOSH recommends that the “most protective” respirators be worn for all varieties of crystalline silica at concentrations above 25 mg/m3.]
							
					
						Page last reviewed:  December 4, 2014					Content source: 	National Institute for Occupational Safety and Health NIOSH Publications & Products
Immediately Dangerous To Life or Health (IDLH) Values
Table of IDLH Values
Criteria for Determining IDLH Values
Historical Documentation
Original (SCP) Values
Abbreviations for IDLH Documentation
Abbreviations for Journal Titles Follow NIOSH Facebook
Pinterest
Twitter
YouTube
 NIOSH Homepage NIOSH A-Z
Workplace Safety & Health Topics
Publications and Products
Programs
Contact NIOSH


About CDC
					Contact Us
					800-232-4636
 Facebook Twitter Instagram LinkedIn Youtube Pinterest Snapchat
 CONTACT CDC
				Contact Us
							Call 800-232-4636
							Email Us
			ABOUT CDC
				About CDC
							Jobs
							Funding
			POLICIES
				Accessibility
							External Links
							Privacy
							Policies
							No Fear Act
							FOIA
							OIG
							Nondiscrimination
							Vulnerability Disclosure Policy
			CONNECT WITH US
				Facebook
								Twitter
								Instagram
								LinkedIn
							Youtube
								Pinterest
								Snapchat
								Email
			LANGUAGES
				Español
							繁體中文
							Tiếng Việt
							한국어
							Tagalog
							Русский
							العربية
							Kreyòl Ayisyen
							Français
							Polski
							Português
							Italiano
							Deutsch
							日本語
							فارسی
							English


U.S. Department of Health & Human Services
			Accessibility
			External Links
			Privacy
			Policies
			No Fear Act
			FOIA
			Nondiscrimination
			OIG
			Vulnerability Disclosure Policy
			USA.gov


Exit Notification / Disclaimer Policy Close
 Links with this icon  indicate that you are leaving the CDC website. The Centers for Disease Control and Prevention (CDC) cannot attest to the accuracy of a non-federal website.
				Linking to a non-federal website does not constitute an endorsement by CDC or any of its employees of the sponsors or the information and products presented on the website.
				You will be subject to the destination website's privacy policy when you follow the link.
				CDC is not responsible for Section 508 compliance (accessibility) on other federal or private website. Website Disclaimers
 Cancel Continue