SILICA EXPOSURES IN THE 

METAL/NONMETAL (M/NM) 

MINING INDUSTRY 

Bruce B. Palmer, M.P.H. 

Health Specialist 

MSHA M/NM Western District 

September 28, 2010 
What is “Silica”?

 SiO2 (e.g., sand, glass, etc.) 

 Silicates (e.g., asbestos) is a chemical

cousin 

 This presentation will only address 

respirable crystalline silica in the quartz, 

cristobalite, and tridymite forms 
Types of Mines Where Silica is Found 

 Almost all mines – including coal 

 Percent in ore varies considerably, even 

within same commodity and location 
MSHA Targeting of Respirable Silica 

 MSHA has targeted respirable quartz 

for 33 years; it has been a Government 

Performance and Results Act (GPRA) 

goal for approximately 8 years 
What is GPRA?? 

 GPRA – Government Performance and 

Results Act, congressional legislation 

that requires government agencies to 

prepare strategic plans and annual 

performance goals

 In MSHA M/NM, GPRA health goals 

have historically been associated with 

sampling toxic contaminants 
What is the Overall Objective of 

M/NM GPRA Goals? 

 Encourage consistent sampling of toxic 

contaminants at mines throughout the U.S. 

 Focus on the contaminants that have the 

greatest likelihood of damaging miners’ health 

 Identify trends so far as feasible 

 BOTTOM LINE: Reduce exposure to miners 

to toxic contaminants 
FY2010 M/NM GPRA Goals 

Included: 

2010 Metal/Nonmetal Health Sampling Program 

Goal: Reduce Work-Related Illnesses in Metal & Nonmetal Mines 

Sampling Annually 

 10 Contaminants: Asbestos, Beryllium Dust, Calcium Oxide, 

Cristobalite, Cyanide, Lead, Mercury, Radiation-Alpha, RadiationGamma, Silica 

 100% of Identified Commodity Mines: Asbestos, Beryl-Beryllium 

Ore, Ground Silica, Vermiculite, Cement, Lime, Crushed & Broken 

Quartzite, Diatomaceous Earth (Diatomite), Ground Cristobalite, 

Lead, Lead-Zinc Ore, Zinc, Gold, Uranium Ore, Uranium-Vanadium 

Ore, Vanadium Ore 

Sampling Every 5 Years 

 10 Contaminants: Chromium VI, Diesel Particulate, Noise, 

Radiation-Alpha, Respirable Dust, Silver, Sulfuric Acid, Talc Fiber, 

Welding Fumes 

 Reported Musculoskeletal Illnesses within Last 5 Years 

 

 20% of Mines Sampled Each Year 
FY2010 M/NM GPRA Goals 

included: 

Reduce Work-Related Illnesses in Metal & Nonmetal Mines 

Sampling Annually 

 10 Contaminants: Asbestos, Beryllium Dust, Calcium Oxide, Cristobalite, Cyanide, 

Lead, Mercury, Radiation-Alpha, Radiation-Gamma, Silica 

 100% of Identified Commodity Mines: Asbestos, Beryl-Beryllium Ore, Ground 

Silica, Vermiculite, Cement, Lime, Crushed & Broken Quartzite, Diatomaceous Earth 

(Diatomite), Ground Cristobalite, Lead, Lead-Zinc Ore, Zinc, Gold, Uranium Ore, 

Uranium-Vanadium Ore, Vanadium Ore 

Sampling Every 5 Years 

 10 Contaminants: Chromium VI, Diesel Particulate, Noise, Radiation-Alpha, 

Respirable Dust, Silver, Sulfuric Acid, Talc Fiber, Welding Fumes 

 Reported Musculoskeletal Illnesses within Last 5 Years 

 20% of Mines Sampled Each Year
FY2011 M/NM GPRA Goals will 

change:

Emphasis on enforcement of 56/57.5002

 M/NM sampling strategy will be to sample 

20% of our mines each year during the next 

5 years. 

 Our goal will be to increase the percentage of 

mines conducting their own surveys. 

 In 5 years, ensure compliance of 56/57.5002 

at all of our mines. 
2005–2009 MSHA Sampling 

for Respirable Dust (Silica) 

Citable Overexposures 

(>TLV) but not 

citable 

> 1⁄2 TLV but 

< TLV 

 

Cumulative 

5% 2% 12% 19%
Factors Affecting Overexposure 

 Trending 

 MSHA management commitment to 

sampling 

 Mine management commitment to dust 

controls 

 Training of inspectors 

 Commodity mined 

 Job sampled 

 Effectiveness of dust controls 
What Does MSHA Require of 

Mine Operators? 

Comply with 56/57.5001, .5002, .5005, and 

Part 58 
What Does MSHA Require of 

Mine Operators? 

.5001: Not exceed 1973 ACGIH TLVs 
What Does MSHA Require of 

Mine Operators? 

 .5002: “Dust...surveys shall be 

conducted as frequently as necessary to 

determine the adequacy of control 

measures”
What Does MSHA Require of 

Mine Operators? 

.5005: Control of Exposure 

 “...insofar as feasible, by prevention of contamination, 

removal by exhaust ventilation, or by dilution with 

uncontaminated air”

 “...Whenever respiratory protective equipment is used 

[implement] a program for selection, maintenance, 

training, fitting, supervision, cleaning, and 

use...consistent with...ANSI Z88.2-1969 [and 

furnish/use] respirators approved by NIOSH under 42 

CFR part 84 which are applicable and suitable for the 

purpose intended”
What Does MSHA Require of 

Mine Operators? 

 58.610: use of enclosed device or 

respirators approved under 42 CFR 84 

when abrasive blasting 
What Does MSHA Require of 

Mine Operators? 

58.620: Drill Dust Control 

 “...effective dust control measures shall 

be used...”
What Does MSHA Require of Mine 

Operators for 56/57.5002? 

 A performance-based standard applicable to 

each unique mining environment, not an 

overarching prescriptive standard 

 Program Policy Letter coming out 

 How much is “enough”?

“...surveys shall be conducted as frequently as necessary to 

determine the adequacy of control measures”

 MSHA will ask for operator’s records as 

evidence of their surveys 

 MSHA website will have more information 
What Guidance Does the MSHA 

Program Policy Manual Provide? 

 “The sampling and analytical methods 

used by the mine operator should be 

consistent with established scientific 

principles....” 
What if Operator Sampling Records 

Show a Past overexposure? 

 Will MSHA issue a citation for 

overexposure identified through operator 

sampling? 

– NO! 

 Can MSHA resample the job/location 

where the operator exposure occurred? 

– Of Course! 
P-Codes 

• What is a P-Code? 

• A code added to MSHA sampling 

documentation signifying that “citable 

overexposure occurred, but all feasible 

engineering and administrative controls have 

been implemented...”

• When a P-Code is issued (by MSHA 

headquarters with District recommendation) 

any subsequent citation is not issued 

BUT...
What About Issuing a P-Code? 

• P-Codes apply to NOISE ONLY 

• Also FYI...operators do not request P-Codes.

[Requests are initiated by MSHA District 

Managers based on a history of noise 

overexposure and good faith efforts of operators 

to control the noise for the particular job & 

location] 
What is the Current MSHA M/NM 

Standard? 

 Current standard is based on 1973 

ACGIH TLV: 

• Quartz: 10 mg/m3

 % respirable Q + 2 

• Cristobalite: 1⁄2 value calculated for quartz 

• Tridymite: 1⁄2 value calculated for quartz 

“Designed to limit exposures to 0.1 mg/m3”
Respirable Crystalline 

Silica Standard 

 MSHA’s agenda is to publish a “notice of 

proposed rule making” in 4/2011

 See 

http://www.msha.gov/REGS/UNIFIED/Ap

ril2010/1219-AB36.asp#

 Check www.msha.gov for updates 
Respirable Crystalline 

Silica Standard 

 DOL/MSHA RIN: 1219-AB36 Publication ID: Spring 2010 

 Title: Respirable Crystalline Silica Standard 

 Abstract: Current standards limit exposures to quartz (crystalline silica) in respirable dust. The coal mining industry standard is based on the 

formula 10 mg/m3 divided by the percentage of quartz where the quartz percent is greater than 5 percent calculated as an MRE equivalent 

concentration. 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. Overexposure to crystalline silica can result in some 

miners developing silicosis, an irreversible but preventable lung disease, which ultimately may be fatal. Both formulas are designed to limit 

exposures to 0.1 mg/m3 (100 ug) of silica. The Secretary of Labor's Advisory Committee on the Elimination of Pneumoconiosis Among Coal Mine 

Workers made several recommendations related to reducing exposure to silica. 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: Long-Term Actions 

 Major: No Unfunded Mandates: No 

 CFR Citation: 30 CFR 56 to 57; 30 CFR 70 to 72; 30 CFR 90 (To search for a specific CFR, visit the Code of Federal Regulations.) 

 Legal Authority: 30 USC 811; 30 USC 813 

 Legal Deadline: None 

 Statement of Need: MSHA standards are outdated; 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, adapting it as necessary 

for the mining industry. 

 Summary of the Legal Basis: Promulgation of this standard is authorized by sections 101 and 103 of the Federal Mine Safety and Health Act of 

1977. 

 Alternatives: This rulemaking would amend and improve health protection from that afforded by the existing standard. MSHA will consider 

alternative methods of addressing miners' exposure 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. 

 Risks: 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' 

exposure to respirable crystalline silica. 

 Timetable: 

 Action Date FR Cite 

 NPRM 04/00/2011 
Respirable Crystalline 

Silica Standard 

RISKS: 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' exposure 

to respirable crystalline silica. 
Respirable Crystalline 

Silica Standard 

 NEED: MSHA standards are outdated; 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, adapting it as 

necessary for the mining industry. 
Respirable Crystalline 

Silica Standard 

ALTERNATIVES: This rulemaking would 

amend and improve health protection from 

that afforded by the existing standard. MSHA 

will consider alternative methods of 

addressing miners' exposure based on the 

capabilities of the sampling and analytical 

methods. 
Respirable Crystalline 

Silica Standard 

ABSTRACT: Current standards limit exposures to quartz (crystalline silica) 

in respirable dust. 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. Overexposure to crystalline silica can 

result in some miners developing silicosis, an irreversible but preventable 

lung disease, which ultimately may be fatal. Formulas are designed to limit 

exposures to 0.1 mg/m3 (100 ug) of silica. The Secretary of Labor's 

Advisory Committee on the Elimination of Pneumoconiosis Among 

Coal Mine Workers made several recommendations related to 

reducing exposure to silica. 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. 
QUESTIONS?