NIOSH Mining Program

R.J. Matetic, PhDDirector, Pittsburgh Mining Research Division

NIOSH Information for NAS Committee on Respirable Coal Dust

NAS Statement of Task

Compare the monitoring technologies and sampling protocols (including sampling frequency) currently used or required in the United States, and in similarly industrialized countries for the control of respirable coal mine dust exposure in underground coal mines.

Assess the effects of rock dust mixtures and their application, as required by current U.S. regulations, on respirable coal mine dust measurements.

Assess the efficacy of current monitoring technologies and sampling approaches, and develop science-based conclusions regarding optimal monitoring and sampling strategies to aid mine operators' decision making related to reducing respirable coal mine dust exposure to miners in underground coal mines.

An ad hoc committee will…

NIOSH topics coveredExposure risk evidence provided for MSHA’s respirable dust rule

Dust monitoring technologies

Current dust control research

Rock dusting recommendations and impact on dust monitoring

Other output information that may be useful to the committee

Exposure risk evidence provided for MSHA’s respirable dust rule

Evidence: CWP is related to coal dust concentration, age, and coal rank

Study Coal rank Disease category Concentration0.5 mg/m3 1.0 mg/m3 2.0 mg/m3

Attfield & Seixas(1995)

High-rank bituminousCWP ≥ 1 48 119 341CWP ≥ 2 20 58 230PMF 13 36 155

Medium/low-rank bituminous CWP ≥ 1 27 63 165CWP ≥ 2 9 22 65PMF 4 10 29

Attfield & Morring(1992)

AnthraciteCWP ≥ 1 45 120 380CWP ≥ 2 17 51 212PMF 17 46 167

High-rank bituminous(89% carbon)

CWP ≥ 1 41 108 338CWP ≥ 2 15 43 168PMF 13 34 114

Medium/low-rank bituminous(83% carbon)

CWP ≥ 1 18 42 111CWP ≥ 2 6 15 42PMF 4 9 21

Medium/low-rank bituminous(Midwest)

CWP ≥ 1 12 26 64CWP ≥ 2 4 9 22PMF 1 3 6

Medium/low-rank bituminous(West)

CWP ≥ 1 7 14 32CWP ≥ 2 <1 <1 1PMF <1 <1 1

Highest risk occupations

Occupation Coal samplesCoal samples > 2.0 mg/m3

Quartz samples

Quartz samples > 100 µg/m3

Tailgate shearer operator

5,307 13.7% 1,995 10.5%

Jack setter 10,852 10.7% 747 14.3%Continuous miner operator

80,654 7.9% 31,181 13.3%

Roof bolter operator 98,081 4.0% 2,632 9.8%

MSHA inspector samples from 2000 through 2015

Coal mine dust exposure and miner health effects

1995 - Criteria for a recommended standard: occupational exposure to respirable coal mine dust [NIOSH Publication No. 95–106]

Establishes REL of 1 mg/m3. Since REL does not assure zero risk over a working lifetime, also recommends:• Keeping worker exposures as far below the REL as feasible• Frequent monitoring of worker exposures• Participation of miners in recommended medical screening and surveillanceNotes that the NIOSH REL for respirable crystalline silica is 0.05 mg/m3

2011 - Current Intelligence Bulletin 64: Coal mine dust exposures and associated health outcomes; a review of information published since 1995 [NIOSH Publication No. 2011-172]

• Reviewed newer literature and found that the 1995 recommendations remained valid.

Coal mine dust exposure and miner health effects – GAO support2012 - Reports and Key Studies Support the Scientific Conclusions Underlying the Proposed Exposure Limit for Respirable Coal Mine Dust [GAO-12-832R]

Government Accountability Office supported “…the conclusion that lowering the PEL from 2.0 mg/m3 to 1.0 mg/m3 would reduce miners’ risk of disease.”

2014 - Basis for proposed exposure limit on respirable coal mine dust and possible approaches for lowering dust levels [GAO-14-345]

MSHA appropriately did not use recent trend data on coal workers' pneumoconiosis (CWP) as a basis for its proposal to lower the permissible exposure limit for respirable coal mine dust.

MSHA primarily based its proposed new limit on two reports and six epidemiologic studies, which each concluded that lowering the limit on exposure to coal mine dust would reduce miners' risk of developing disease.

Dust monitoring technologies

Continuous Personal Dust Monitor (CPDM)

CPDM performance attributes

• Mass-based determination of concentration (TEOM)

• Heated sample path to drive off moisture

• Time-weighted-average dust concentration displayed on unit

• Respirable dust concentration recorded every one minute in internal file

• Key instrument operating parameters also recorded each minute in file

• End-of-shift concentration shown on unit and in data file

• Secure data file transmitted to MSHA with CPDM software

Airflow

Filter

TaperedElementOscillatingMicrobalance

MSHA uses some of this information in determining voided samples.

PDM record of numerous operating parameters helps in identifying valid sample collection. For example:

Pump flow rate Identifies correct volume of air (pinched sampling hose)

Mass on filter Identifies large gain/loss of mass on filter, which may result from inlet falling into dust pile or dropping PDM which knocks dust off of filter

Temperature of TEOM

Temperature control ensures accuracy of dust mass measurement

Tilt sensor Identifies movement of PDM

NIOSH testing of CPDM performance – key publicationsPerformance of a new personal respirable dust monitor for mine use [NIOSH 2004-151] • Prototype device tested -- limited underground trials• Met NIOSH accuracy criterion ±25% of the reference measurements

Laboratory and field performance of a continuously measuring personal respirable dust monitor [NIOSH 2006-145]• Pre-commercial device tested (not yet certified)• Field tested at 20% of MMUs, 10% of longwalls

Equivalency of a personal dust monitor to the current United States coal mine respirable dust sampler [Journal of Environmental Monitoring, 2008]• CPDM under samples slightly – 1.05 conversion multiplier

Respirable dust standards and sampling methods vary by country.

Country Respirable coal dust, mg/m3

Respirable quartz, µg/m3 Dust sampler

Flow rate, Lpm

United States 1.5 100 CPDM 2.2Australia – New South Wales 2.5 120 Gravimetric 1.7Australia – Queensland 3.0 100 Gravimetric 1.7South Africa 2.0 100 Gravimetric 2.2

Efficacy of current monitoring technologies

CPDM designed to empower workers and management with exposure information during the work shift in order to avoid overexposures

Dust sampler Sampling periodPercent greater than standard

Gravimetric 8/1/2014 – 1/31/2016 2.2%CPDM 4/1/2016 – 7/31/2016 0.3%

CPDM has dropped overexposure rate for operator samples by over 86%

Efficacy of current monitoring technologies

• CPDM does not provide capability for silica analysis

• PMRD researchers are developing a method for conducting an end-of-shift silica analysis method for gravimetric filter samples

Best Practices for Dust Control in Coal Mining[IC9517 – NIOSH Publication No. 2010-110]

Contents• Health effects of overexposure to respirable coal and

silica dust

• Sampling to quantify respirable dust generation

• Controlling respirable dust on longwall mining operations

• Controlling respirable dust on continuous mining operations

• Controlling respirable silica dust at surface mines

NIOSH dust control publications since handbook

Evaluation of face dust concentrations at mines using deep-cut practices. [2011]. RI 9680, NIOSH Publication No. 2011-131.

Dust capture performance of a water exhaust conditioner for roof bolting machines. [2012] Mining Engineering, 64(3):45-49.

Development of a canopy air curtain to reduce roof bolters' dust exposure. [2012] Mining Engineering, 64(7):72-79.

Silica and respirable content in rock dust samples. [2012] Coal Age, 117(12):48-52.

Examination of water spray airborne coal dust capture with three wetting agents. [2013] SME Annual Meeting, Preprint 13-022.

NIOSH dust control publications since handbook

Impact of operating a flooded-bed scrubber on respirable dust levels in 20-foot cuts. [2013] RI 9693, NIOSH Publication No. 2014-105.

Examination of redirected continuous miner scrubber discharge configurations for exhaust face ventilation systems. [2013] SME Transactions, Vol 334:427-434.

Evaluations of bit sleeve and twisted-body bit designs for controlling roof bolter dust. [2015] Mining Engineering, 67(2):34-40.

Evaluating tailgate spray manifolds to reduce dust exposures for shearer face personnel. [2015] SME Annual Meeting, Preprint 15-077.

Influence of continuous mining arrangements on respirable dust exposures. [2015] SME Annual Meeting, Preprint 15-004.

NIOSH dust control publications since handbook

Examination of a newly developed mobile dry scrubber (DS) for coal mine dust control applications. [2016] SME Annual Meeting, Preprint 16-010.

Development of a roof bolter canopy air curtain for respirable dust control. [2016] SME Annual Meeting, Preprint 16-003.

CFD analysis on gas distribution for different scrubber redirection configurations in sump cut. [2016] SME Transactions, Vol 338.

Dust control publications accepted for 2017 SME Annual Meeting

Comparison of different hollow cone water sprays for continuous miner dust control applications. February 21, 2017.

Material property tests of foam agents to determine their potential for longwall mining dust control research. February 21, 2017.

Assessing foam application to mine roof for longwall mining shield dust control. February 22, 2017.

NIOSH silica-related dust publications Pneumoconiosis among underground bituminous coal miners in the United States: is silicosis becoming more frequent? 2010. Occupational and Environmental Medicine, 67(10):652-656]

The increasing prevalence of pneumoconiosis over the past decade and the change in the epidemiology and disease profile documented in this and other recent studies imply that U.S. coal miners are being exposed to excessive amounts of respirable crystalline silica.

Resurgence of Progressive Massive Fibrosis in Coal Miners — Eastern Kentucky, 2016. [Morbidity and Mortality Weekly Report 65(49): 1385-1389]

During January 1, 2015–August 17, 2016, a total of 60 patients identified through a single radiologist’s practice had radiographic findings consistent with PMF.

Current dust control research

Ongoing intramural research effortsControlling Respirable Dust in Coal Mining Operations

• Develop underside canopy shield spray systems to reduce dust generated by spalling

• Develop foam applications to the longwall roof to mitigate dust during shield advance

• Investigate the use of shearer-mounted, water-powered dust collectors

• Investigate operating parameters to reduce shuttle car operator dust levels with blowing face ventilation

Monitoring and Control of Airborne Toxic Substances in Mining• Evaluate solutions for in-field, end-of-shift crystalline silica analysis• Fulfill statutory requirements of 30 CFR Part 74 to evaluate and

certify respirable dust samplers for coal mine use

Ongoing extramural research efforts

Miniaturized coal and dust monitors• Broad Agency Announcement closed 1/17/2017

Canopy air curtain for shuttle cars• Contract with Marshall University and J.H.

Fletcher & Co.

Flooded bed scrubber for longwall shearers• Cooperative study with UK funded by Alpha

foundation

Rock dusting recommendations and impact on dust monitoring

Rock dusting requirements: 2010 NIOSH recommendationsRecommendation for new standard driven by changes since original 1920s surveys:• Larger mine geometries• Finer-sized coal dust particles due to larger & more

powerful equipment• Propagates more readily• More rock dust required to inert

Recommended increase from 65% to 80% incombustible content in intake airways(standard for returns was already 80%)

Rock dusting and monitoring increased after NIOSH 2010 recommendations

• MSHA 2010 Emergency Temporary Standard - Maintenance of Incombustible Content of Rock Dust in Underground Coal• Requires 80% incombustible content in intakes

• Increased need for tools to measure incombustible content• Addressed by CDEM

• Concerns about impact on dust monitoring• Addressed by MSHA exceedances, NIOSH studies• Reduced respirable component in rock dust

• But did not inert effectively• Foam and wet rock dust

NIOSH rock dusting publications

Review of Rock Dusting Practices in Underground Coal [NIOSH Publication No. 2017-101, IC 9530].

• A comprehensive review of rock dusting practices in the industry.

Design and development of a dust dispersion chamber to quantify the dispersibility of rock dust [J Loss Prev Process Ind 2016 Jan; 39:7-16]

• New test method to assess rock dust dispersion• Uses reproducible pulse of air• Quantifies obscuration of a dust probe beam

Participation of large particles in coal dust explosions [J Loss Prev Process Ind 2014 Jan; 27:49-54]. The results show:

• Large coal particles >60 mesh (>250 µm) do not explode/ignite at dust concentrations up to 600 g/m3

• Limestone rock dust particles >200 mesh (>75 µm) require a significantly higher TIC of 90% to inert Pittsburgh pulverized coal (PPC)

NIOSH rock dusting publications

Particle Size and Surface Area Effects on Explosibility Using a 20-L Chamber [J Loss Prev Process Ind 2015 Sep; 37:33-38] • Dust particle size has the greatest influence on the propagation (coal dust) and inhibition

(rock dust) of dust explosions.• Samples collected from the MSHA rock dust survey (as discussed in the 2011 NIOSH

Hazard ID), were multi-modal, and several samples appeared to have wide variations in the amount of effective finer particles.

• Rock dust particles from 200 mesh to 60 mesh are largely ineffective in inerting coal dust explosions.

• Rock dust particles < 38 μm are more effective in inerting coal dust.• The inerting effectiveness of rock dust is correlated to the specific surface area (SSA) of

the rock dust• Results suggest the need to include a minimum SSA as a critical specification for

effective rock dust.• Shows that rock dust is most effective for inerting propagating coal mine dust explosions

if the particle size is at least 95 percent finer than 200 mesh or 75 μm, and more importantly has a minimum surface area of 260 m2/kg.

Other output information that may be useful to the committee

Useful information on CPDM and sampling

1. What changes/improvements should be incorporated into the next generation of real-time dust samplers?

2. What are the most common problems with the CPDM that mining companies are experiencing?

3. How are mines using results from the CPDM?4. How do miners who are required to sample with the CPDM wear the unit? Is it placed on

their machine?5. How often do the face boss and/or miner check the dust readings on the CPDM?6. What cumulative dust concentration reading on the PDM must be reached in order to

initiate a change in dust controls?7. What changes in personnel and practices have mines made to accomplish the sampling

required under the new respirable dust rule?

Useful information on rock dust practices

1. Where in the mining cycle or under what conditions do rock dust applications have the greatest adverse impact on respirable dust sampling?

2. Have mines changed their rock dusting practices and, if so, how?3. Based on 1 and 2, what research and other steps should NIOSH take?

Useful information on use of rock dust to prevent coal dust explosions

1. What is the committee’s perception of an ideal rock dust? What characteristics would that material possess?

2. Are there areas in an underground coal mine where dispersible rock dust may be effectively used?

3. Based on 1 and 2, recommendations for coal dust monitoring and rock dust requirements

Disclaimer: The findings and conclusions in this report are those of the author(s) and do not necessarily represent the views of the National Institute for Occupational Safety and Health. Mention of any company or product does not constitute endorsement by NIOSH.

NIOSH Mining Program – www.cdc.gov/niosh/mining

For more information

R.J. Matetic - RMatetic@cdc.gov - 412-386-6601

Resource list: www.cdc.gov/niosh/mining/coaldustresources.html

International rock dusting requirementsCountry TIC % Volatile matter % Methane % CommentsUnited States 80 (intake)

80 (return)——

1.0 / 0.10.4 / 0.1

Add 1% TIC / 0.1% methaneAdd 0.4% TIC / 0.1% methane

Australia Queensland

85–80 (return)85–70 (intake)

——

85% TIC ≤ 200 m from the face 80% TIC > 200 m from the face85% TIC ≤ 200 m from the face 70% TIC > 200 m from the face Supplemental protection—barriers

Australia NSW 85–70 (return)80–70 (intake)

——

85% TIC ≤ 200 m from the face 70% TIC > 200 m from the face 80% TIC ≤ 200 m from the face 70% TIC > 200 m from the face Supplemental protection—barriers

Canada (Nova Scotia)

75 (intake)80 (return)

——

<1>1

Czech Republic 80 (intake/return)85 (intake/return)

——

<1>1

Supplemental protection—barriers

Slovakia 80 (intake/return)85 (intake/return)

——

<1>1

Supplemental protection—barriers

Germany 80 (intake/return) — Supplemental protection—barriersJapan 78 (intake/return)

83 (intake/return)3535

<1>1

Specific requirements depend on ash, moisture and volatile content, the gassiness of the seam, and the fineness of the rock dust used.

Poland 70 (intake/return) >10>10

70% in “non-gassy” roadways 80% in “gassy” roadways Supplemental protection—barriers

South Africa 80 (intake) ——

80 % TIC ≤ 200 m from the face 65% TIC > 200 m from the face 80% TIC for 1000 m from the face Supplemental protection—barriers

United Kingdom 50 (intake/return)65 (intake/return)72 (intake/return)75 (intake/return)

202735

>35

Supplemental protection—barriers