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DOL/MSHA RIN: 1219-AB36 Publication ID: Fall 2016 
Title: Respirable Crystalline Silica  

Current MSHA standards limit exposures to quartz (crystalline silica) in respirable dust. Overexposure to crystalline silica can result in some miners developing silicosis, an irreversible but preventable lung disease, which ultimately may be fatal. The metal and nonmetal mining industry standard is based on the 1973 American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Values formula: 10 mg/m3 divided by the percentage of quartz plus 2. The formula is designed to limit exposures to 0.1 mg/m3 (100 ug/m3) of silica. The National Institute for Occupational Safety and Health (NIOSH) recommends a 50 ug/m3 exposure limit for respirable crystalline silica. MSHA will publish a proposed rule to address miners' exposure to respirable crystalline silica.

Agency: Department of Labor(DOL)  Priority: Other Significant 
RIN Status: Previously published in the Unified Agenda Agenda Stage of Rulemaking: Proposed Rule Stage 
Major: No  Unfunded Mandates: No 
CFR Citation: 30 CFR 58   
Legal Authority: 30 U.S.C. 811   
Legal Deadline:  None

Statement of Need:

MSHA standards have not been updated since 1985; current regulations may not protect workers from developing silicosis. Evidence indicates that miners continue to develop silicosis. MSHA's proposed regulatory action exemplifies the Agency's commitment to protecting the most vulnerable populations while assuring broad-based compliance. MSHA will regulate based on sound science to eliminate or reduce the hazards with the broadest and most serious consequences. MSHA intends to use OSHA's work on the health effects and risk assessment of silica, adapting it as necessary for the mining industry.

Summary of the Legal Basis:

Promulgation of this standard is authorized by section 101 of the Federal Mine Safety and Health Act of 1977.


This rulemaking would improve health protection from that afforded by the existing standards. MSHA will consider alternative methods of addressing miners' exposures based on the capabilities of the sampling and analytical methods.

Anticipated Costs and Benefits:

MSHA will prepare estimates of the anticipated costs and benefits associated with the proposed rule.


For over 70 years, toxicology information and epidemiological studies have shown that exposure to respirable crystalline silica presents potential health risks to miners. These potential adverse health effects include simple silicosis and progressive massive fibrosis (lung scarring). Evidence indicates that exposure to silica may cause cancer. MSHA believes that the health evidence forms a reasonable basis for reducing miners' exposures to respirable crystalline silica.

Action Date FR Cite
NPRM  04/00/2017 
Regulatory Flexibility Analysis Required: Undetermined  Government Levels Affected: Local, State 
Small Entities Affected: Businesses, Governmental Jurisdictions  Federalism: No 
Included in the Regulatory Plan: Yes 
RIN Information URL:   Public Comment URL:  
RIN Data Printed in the FR: No 
Agency Contact:
Sheila McConnell
Director, Office of Standards, Regulations, and Variances
Department of Labor
Mine Safety and Health Administration
201 12th Street South, Room 4E401,
Arlington, VA 22202-5452
Phone:202 693-9440
Fax:202 693-9441