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DOL/OSHA RIN: 1218-AB70 Publication ID: Spring 2016 
Title: Occupational Exposure to Crystalline Silica 

Crystalline silica is a significant component of the earth's crust, and many workers in a wide range of industries are exposed to it, usually in the form of respirable quartz or, less frequently, cristobalite. Chronic silicosis is a uniquely occupational disease resulting from exposure of employees over long periods of time (10 years or more). Exposure to high levels of respirable crystalline silica causes acute or accelerated forms of silicosis that are ultimately fatal. The current OSHA permissible exposure limit (PEL) for general industry is based on a formula proposed by the American Conference of Governmental Industrial Hygienists (ACGIH) in 1968 (PEL=10mg/cubic meter/(% silica + 2), as respirable dust). The current PEL for construction and shipyards (derived from ACGIH's 1970 Threshold Limit Value) is based on particle counting technology, which is considered obsolete. NIOSH and ACGIH recommend 50µg/m3 and 25µg/m3 exposure limits, respectively, for respirable crystalline silica. 

Both industry and worker groups have recognized that a comprehensive standard for crystalline silica is needed to provide for exposure monitoring, medical surveillance, and worker training. ASTM International has published recommended standards for addressing the hazards of crystalline silica. The Building Construction Trades Department of the AFL-CIO has also developed a recommended comprehensive program standard. These standards include provisions for methods of compliance, exposure monitoring, training, and medical surveillance.

The NPRM was published on September 12, 2013 (78 FR 56274). OSHA received over 1,700 comments from the public on the proposed rule, and over 200 stakeholders provided testimony during public hearings on the proposal. The agency is now reviewing and considering the evidence in the rulemaking record. 

Agency: Department of Labor(DOL)  Priority: Economically Significant 
RIN Status: Previously published in the Unified Agenda Agenda Stage of Rulemaking: Completed Actions 
Major: Yes  Unfunded Mandates: Private Sector 
CFR Citation: 29 CFR 1910    29 CFR 1915    29 CFR 1917    29 CFR 1918    29 CFR 1926   
Legal Authority: 29 U.S.C. 655(b)    29 U.S.C. 657   
Legal Deadline:  None

Statement of Need:

Workers are exposed to crystalline silica dust in general industry, construction, and maritime industries. Industries that could be particularly affected by a standard for crystalline silica include: foundries, industries that have abrasive blasting operations, paint manufacture, glass and concrete product manufacture, brick making, china and pottery manufacture, manufacture of plumbing fixtures, and many construction activities including highway repair, masonry, concrete work, rock drilling, and tuckpointing. The seriousness of the health hazards associated with silica exposure is demonstrated by the fatalities and disabling illnesses that continue to occur. From 2009 to 2013 silicosis was identified on over 500 death certificates as an underlying or contributing cause of death. It is likely that many more cases have occurred where silicosis went undetected. In addition, the International Agency for Research on Cancer has designated crystalline silica as carcinogenic to humans, and the National Toxicology Program has concluded that respirable crystalline silica is a known human carcinogen. Exposure to crystalline silica has also been associated with an increased risk of developing tuberculosis and other nonmalignant respiratory diseases, as well as renal and autoimmune diseases. Exposure studies and OSHA enforcement data indicate that some workers continue to be exposed to levels of crystalline silica far in excess of current exposure limits. Congress has included compensation of silicosis victims on Federal nuclear testing sites in the Energy Employees' Occupational Illness Compensation Program Act of 2000. There is a particular need for the Agency to modernize its exposure limits for construction and shipyard workers.

Summary of the Legal Basis:

The legal basis for the proposed rule was a preliminary determination that workers are exposed to a significant risk of silicosis and other serious disease, and that rulemaking is needed to substantially reduce the risk. In addition, the proposed rule recognized that the PELs for construction and maritime are outdated, and need to be revised to reflect current sampling and analytical technologies.


Over the past several years, the Agency has attempted to address this problem through a variety of non-regulatory approaches, including initiation of a Special Emphasis Program on silica in October 1997, sponsorship with NIOSH and MSHA of the National Conference to Eliminate Silicosis, and dissemination of guidance information on its website.

Anticipated Costs and Benefits:

OSHA preliminarily estimated the cost of the proposed rule to be $664 million per year. OSHA preliminarily estimated that the proposed rule would prevent nearly 700 deaths per year and prevent over 1,600 cases of silicosis annually once the full effect of the rule are realized, and would result in monetized benefits of $2.8 to $4.7 billion annually.


A detailed risk analysis is under way.

Action Date FR Cite
Completed SBREFA Report  12/19/2003    
Initiated Peer Review of Health Effects and Risk Assessment  05/22/2009    
Completed Peer Review  01/24/2010    
NPRM  09/12/2013  78 FR 56274   
NPRM Comment Period Extended; Notice of Intention to Appear at Pub Hearing; Scheduling Pub Hearing  10/31/2013  78 FR 65242   
NPRM Comment Period Extended  01/29/2014  79 FR 4641   
NPRM Comment Period Extended End  02/11/2014 
Informal Public Hearing  03/18/2014 
Post Hearing Briefs Ends  08/18/2014 
Final Rule  03/25/2016  81 FR 16285   
Final Rule Effective  06/23/2016 
Regulatory Flexibility Analysis Required: Yes  Government Levels Affected: Federal, Local, State, Tribal 
Small Entities Affected: Businesses  Federalism: Yes 
Included in the Regulatory Plan: Yes 
RIN Data Printed in the FR: Yes 
Agency Contact:
William Perry
Director, Directorate of Standards and Guidance
Department of Labor
Occupational Safety and Health Administration
200 Constitution Avenue NW., FP Building, Room N-3718,
Washington, DC 20210
Phone:202 693-1950
Fax:202 693-1678