Lowering Miners' Exposure to Respirable Coal Mine Dust, Including Continuous Personal Dust Monitors

DEPARTMENT OF LABOR

Mine Safety and Health Administration

30 CFR Parts 70, 71, 72, 75, and 90

RIN 1219-AB64

Lowering Miners' Exposure to Respirable Coal Mine Dust, Including Continuous Personal Dust Monitors

AGENCY:

Mine Safety and Health Administration, Labor.

ACTION:

Final rule.

SUMMARY:

The Mine Safety and Health Administration (MSHA) is revising the Agency's existing standards on miners' occupational exposure to respirable coal mine dust in order to: Lower the existing exposure limits; provide for full-shift sampling; redefine the term “normal production shift”; and add reexamination and decertification requirements for persons certified to sample for dust, and maintain and calibrate sampling devices. In addition, the rule provides for single shift compliance sampling by MSHA inspectors, establishes sampling requirements for mine operators' use of the Continuous Personal Dust Monitor (CPDM), requires operator corrective action on a single, full-shift operator sample, changes the averaging method to determine compliance on operator samples, and expands requirements for medical surveillance of coal miners.

Chronic exposure to respirable coal mine dust causes lung diseases that can lead to permanent disability and death. The final rule will greatly improve health protections for coal miners by reducing their occupational exposure to respirable coal mine dust and by lowering the risk that they will suffer material impairment of health or functional capacity over their working lives.

DATES:

Effective Date:

August 1, 2014. The incorporation by reference of certain publications listed in the rule was approved by the Director of the Federal Register as of October 12, 1999.

FOR FURTHER INFORMATION CONTACT:

Sheila McConnell, Acting Director, Office of Standards, Regulations, and Variances, MSHA, 1100 Wilson Boulevard, Room 2350, Arlington, Virginia 22209-3939. Ms. McConnell can be reached at

mcconnell.sheila.a@dol.gov

(email), 202-693-9440 (voice), or 202-693-9441 (facsimile).

SUPPLEMENTARY INFORMATION:

Table of Contents

I. Executive Summary

A. Purpose of the Regulatory Action

B. Legal Authority for Regulatory Action

C. Summary of Major Provisions

D. Major Provisions in the Proposed Rule That Are Not in the Final Rule

E. Projected Costs and Benefits

II. Introduction and Background Information

A. MSHA's Existing Respirable Dust Standards

B. 1992 Coal Mine Respirable Dust Task Group Report, 1995 NIOSH Criteria Document, and 1996 Dust Advisory Committee Report

C. 2000 and 2003 Plan Verification Proposed Rules

D. 2000 Single Sample Proposed Rule

E. Continuous Personal Dust Monitors (CPDM)

F. Regulatory History of This Final Rule

G. Government Accountability Office Activities

III. Discussion of the Final Rule

A. Health Effects

B. Quantitative Risk Assessment (QRA)

C. Feasibility

IV. Section-by-Section Analysis

V. Executive Order 12866: Regulatory Planning and Review; and Executive Order 13563: Improving Regulation and Regulatory Review

A. Population at Risk

B. Benefits

C. Compliance Costs

D. Net Benefits

VI. Regulatory Flexibility Act and Small Business Regulatory Enforcement Fairness Act

A. Definition of a Small Mine

B. Factual Basis for Certification

VII. Paperwork Reduction Act of 1995

A. Summary

B. Procedural Details

VIII. Other Regulatory Considerations

A. National Environmental Policy Act (NEPA)

B. The Unfunded Mandates Reform Act of 1995

C. The Treasury and General Government Appropriations Act of 1999: Assessment of Federal Regulations and Policies on Families

D. Executive Order 12630: Government Actions and Interference With Constitutionally Protected Property Rights

E. Executive Order 12988: Civil Justice Reform

F. Executive Order 13045: Protection of Children From Environmental Health Risks and Safety Risks

G. Executive Order 13132: Federalism

H. Executive Order 13175: Consultation and Coordination With Indian Tribal Governments

I. Executive Order 13211: Actions Concerning Regulations That Significantly Affect Energy Supply, Distribution, or Use

J. Executive Order 13272: Proper Consideration of Small Entities in Agency Rulemaking

IX. References

X. Appendix A—Excessive Concentration Values

Availability of Information

Federal Register

Publications: Access rulemaking documents electronically at

http://www.msha.gov/regsinfo.htm

or

http://www.regulations.gov.

Obtain a copy of a rulemaking document from the Office of Standards, Regulations, and Variances, MSHA, by request to 202-693-9440 (voice) or 202-693-9441 (facsimile). (These are not toll-free numbers.)

Information Collection Supporting Statement:

The Information Collection Supporting Statement is available at

http://www.reginfo.gov/public/do/PRAMain

on MSHA's Web site at

http://www.msha.gov/regs/fedreg/informationcollection/informationcollection.asp

and at

http://www.regulations.gov.

A copy of the Statement is also available from MSHA by request to Sheila McConnell at

mcconnell.sheila.a@dol.gov

, by phone request to 202-693-9440, or by facsimile to 202-693-9441.

Regulatory Economic Analysis (REA):

MSHA will post the REA on

http://www.regulations.gov

and on MSHA's Web site at

http://www.msha.gov/rea.htm.

A copy of the REA also can be obtained from MSHA by request to Sheila McConnell at

mcconnell.sheila.a@dol.gov

, by phone request to 202-693-9440, or by facsimile to 202-693-9441.

I. Executive Summary

A. Purpose of the Regulatory Action

The purpose of this final rule is to reduce occupational lung diseases in coal miners. Chronic exposure to respirable coal mine dust causes lung diseases including coal workers' pneumoconiosis (CWP), emphysema, silicosis, and chronic bronchitis, known collectively as “black lung.” These diseases are debilitating and can result in disability and premature death. Based on data from the National Institute for Occupational Safety and Health (NIOSH), new cases continue to occur among coal miners. The prevalence rate of lung disease among our nation's coal miners continues despite the fact that incurable black lung is preventable. Additionally, young miners are showing evidence of advanced and seriously debilitating lung disease from excessive dust exposure.

Over the decade 1995-2004, more than 10,000 miners died from black lung.

1

As of December 2011, according to the Department of Labor's Office of Workers' Compensation Programs, Division of Coal Mine Workers'

Compensation, the federal government has paid over $44 billion in Federal Black Lung benefits to beneficiaries (former miners, widows, dependents) since 1970 (U.S. Department of Labor, Division of Coal Mine Workers' Compensation. 2012. Black Lung Program Statistics).

1

http://www.cdc.gov/niosh/docs/2008-143/pdfs/2008-143a-iii.pdf

, DHHS (NIOSH) Publication No. 2008-143a, Work-Related Lung Disease Surveillance Report 2007, Vol. 1, Table 2-4. Coal workers' pneumoconiosis: Number of deaths by state, U.S. residents age 15 and over, 1995-2004, p. 34, September 2008.

The final rule is changed from the proposal. This final rule will reduce coal miners' occupational exposure to respirable coal mine dust. As a result, it will lower their risk of developing black lung disease and suffering material impairment of health or functional capacity.

B. Legal Authority for Regulatory Action

Sections 101(a)(6)(A), 103(h), and 508 of the Federal Mine Safety and Health Act of 1977 (Mine Act), provide the legal authority for this final rule. (30 U.S.C. 811(a)(6)(A), 813(h), and 957).

Section 101 of the Mine Act gives the Secretary of Labor (Secretary) the authority to promulgate mandatory health standards involving toxic materials or harmful physical agents. It requires that the Secretary set standards to assure, based on the best available evidence, that no miner will suffer material impairment of health from exposure to toxic materials or harmful physical agents over his working life. (30 U.S.C. 811(a)(6)(A)). In developing these standards, the Mine Act requires the Secretary to consider the latest available scientific data in the field, the feasibility of the standards, and experience gained under other laws. Id.

Section 103(h) of the Mine Act gives the Secretary the authority to promulgate standards involving recordkeeping. (30 U.S.C. 813(h)). Section 103(h) provides that every mine operator must establish and maintain records and make reports and provide such information as the Secretary may require. Id.

Section 508 of the Mine Act gives the Secretary the authority to issue regulations to carry out any provision of the Act. (30 U.S.C. 957).

C. Summary of Major Provisions

1.

Lowers the Existing Concentration Limits for Respirable Coal Mine Dust.

After August 1, 2016, the concentration limits for respirable coal mine dust are lowered from 2.0 milligrams of dust per cubic meter of air (mg/m

3

) to 1.5 mg/m

3

at underground and surface coal mines, and from 1.0 mg/m

3

to 0.5 mg/m

3

for intake air at underground mines and for part 90 miners (coal miners who have evidence of the development of pneumoconiosis). Lowering the concentration of respirable coal mine dust in the air that miners breathe is the most effective means of preventing diseases caused by excessive exposure to such dust.

2.

Requires the Use of the Continuous Personal Dust Monitor (CPDM).

On February 1, 2016, mine operators are required to use the continuous personal dust monitor (CPDM) to monitor the exposures of underground coal miners in occupations exposed to the highest respirable coal mine dust concentrations and the exposures of part 90 miners. Use of the CPDM is optional for surface coal mines, non-production areas of underground coal mines, and for underground anthracite mines using the full box, open breast, or slant breast mining methods. The CPDM is a new sampling device that measures continuously, and in real-time, the concentration of respirable coal mine dust and provides sampling results at specific time intervals and at the end of the work shift. It is jointly approved for use in coal mines by MSHA and NIOSH under criteria set forth in Title 30, Code of Federal Regulations (30 CFR) part 74. When the CPDM is used, mine operators, miners, and MSHA will be notified of the results in a more timely manner than when the existing approved Coal Mine Dust Personal Sampler Unit (CMDPSU) is used. This will enable mine operators to take earlier action to identify areas with dust generation sources, reduce the dust levels in those areas, and prevent miners from being overexposed.

3.

Redefines the Term “Normal Production Shift”.

The term normal production shift is redefined to require that underground mine operators take respirable dust samples in the mechanized mining unit (MMU) when production is at least 80 percent of the average production over the last 30 production shifts. The MMU is a unit of mining equipment used in the production of material. Under the existing definition, underground mine operators are required to sample when production is at least 50% of the average production reported during the operator's last sampling period (i.e., last set of five valid samples). Under the revised definition, miners will be better protected because samples will be collected during periods that are more representative of normal mining operations and dust levels to which miners are exposed.

4.

Requires Full-Shift Sampling.

The final rule requires the operator to collect respirable dust samples for the full shift that a miner works. If a miner works a 12-hour shift, respirable dust samples must be taken with an approved sampling device for the entire work shift, rather than a maximum of 8 hours as required under the existing standards. Full-shift sampling provides more representative measurements of miners' respirable dust exposures and increases their health protection.

5.

Changes the Averaging Method to Determine Compliance on Operator Samples.

Under existing standards, corrective action is required only after the average of five operator samples exceeds the respirable coal mine dust standard and a citation is issued. This permits miners to be exposed to levels of respirable coal mine dust that exceed the standard without requiring any corrective action by the operator to reduce concentrations to meet the standard. The final rule requires immediate corrective actions to lower dust concentrations when a single, full-shift operator sample meets or exceeds the excessive concentration value (ECV) for the dust standard. These corrective actions will result in reduced respirable dust concentrations in the mine atmosphere and, therefore, will provide better protection of miners from further high exposures.

6.

Provides for the Use of Single, Full-Shift Samples, by MSHA inspectors, to Determine Compliance.

MSHA inspectors will use single, full-shift samples to determine noncompliance with the respirable dust standards. MSHA has determined that the average concentration of respirable dust to which each miner in the active workings of a coal mine is exposed can be accurately measured over a single shift. MSHA is rescinding the “1972 Joint Finding”

2

by the Secretary of the Interior and the Secretary of Health, Education, and Welfare, on the validity of single-shift sampling. MSHA considers a single, full-shift measurement of respirable coal mine dust to “accurately represent” atmospheric conditions (Section 202(f) of the Mine Act) at the sampling location, if the sampling and analytical method used meet the NIOSH Accuracy Criterion. Limiting the respirable dust concentration in the active workings ensures that the respirable dust concentration inhaled by any miner is limited.

2

In 1972, acting under the Federal Coal Mine Health and Safety Act of 1969 (Coal Act), the Secretaries of the Interior and Health, Education and Welfare made a joint finding (1972 Joint Finding), under § 202(f) of the Coal Act, which concluded that a single shift measurement of respirable dust will not, after applying valid statistical techniques to such measurement, accurately represent the atmospheric conditions to which the miner is continuously exposed (37 FR 3833, February 23, 1972).

7.

Expands Medical Surveillance Requirements.

The final rule adds spirometry testing, occupational history,

and symptom assessment to the periodic chest radiographic (x-ray) examinations required to be offered by mine operators to underground miners under NIOSH's existing standards. The additional medical surveillance requirements will alert miners to any abnormal declines in lung function, which is common evidence of Chronic Obstructive Pulmonary Disease (COPD) and not detected by chest x-rays. Notification of reduced lung function will enable miners to be proactive in protecting their health. The final rule extends the same medical surveillance requirements afforded underground miners, including chest x-ray examinations, to surface miners since they are also at risk of developing lung diseases and material impairment of health or functional capacity from exposure to respirable coal mine dust. In addition, the final rule extends part 90 miner transfer rights, which are currently provided to underground miners who have x-ray evidence of pneumoconiosis, to surface miners who have evidence of pneumoconiosis. Under 30 CFR part 90, these miners can elect to work in less dusty atmospheres to prevent the progression of disease. The medical surveillance requirements will provide improved health protection for all coal miners.

8.

Strengthens Requirements for Certified Persons.

The final rule revises requirements for certified persons who perform dust sampling and who maintain and calibrate sampling equipment. To strengthen the certification process, the final rule adds a requirement that persons must complete an MSHA course of instruction. This complements the existing requirement that, to be certified, the candidate must pass an MSHA examination to demonstrate competency in the tasks needed for respirable dust sampling procedures and in maintenance and calibration procedures. Completing the MSHA course and passing the MSHA examination will ensure that only trained persons perform these important functions. Certified persons are required under the final rule to pass the MSHA examination every three years to maintain their certification. The final rule adds procedures allowing MSHA to revoke a person's certification for failing to properly carry out the required sampling or maintenance and calibration procedures.

The final rule was strategically developed to provide a comprehensive, integrated approach to achieve MSHA's goal of reducing miners' exposure to respirable coal mine dust in a protective and feasible manner.

D. Major Provisions in the Proposed Rule That Are Not in the Final Rule

1.

Sampling Frequency.

The proposed rule would have required that CPDM sampling be conducted 7 days per week, 52 weeks per year for occupations exposed to the highest respirable coal mine dust concentrations and for part 90 miners.

2.

CPDM Performance Plan.

The proposed rule would have required operators who use CPDMs to develop and submit for approval a CPDM Performance Plan prior to using the sampling devices.

3.

Revisions to the Approved Ventilation Plan.

The proposed rule would have required operators to submit to the District Manager for approval the corrective actions to lower respirable dust concentrations.

4.

Equivalent 8-hour Concentration.

The proposal would have required the respirable coal mine dust sampled to be expressed in terms of an 8-hour equivalent concentration for shifts longer than 8 hours.

5.

Separate Intake Air for each MMU.

The proposed rule would have required a separate intake airway for each MMU.

E. Projected Costs and Benefits

• Lowers miners' exposure to respirable coal mine dust, thus reducing and preventing Black Lung.

• Significant reductions in CWP, progressive massive fibrosis (the most severe stage of CWP), severe emphysema, and deaths from non-malignant respiratory disease.

• Estimated annualized benefits: $36.9 million: (3% discount rate) and $20.0 million (7% discount rate).

• Estimated annualized costs: $24.8 million (3% discount rate) and $28.1 million (7% discount rate).

II. Introduction and Background Information

This final rule promotes the Secretary of Labor's vision of “Promoting and Protecting Opportunity”

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and supports the Department of Labor's (DOL's) goal of securing safe and healthy workplaces, particularly for vulnerable workers in high-risk industries such as mining, by reducing workplace deaths and improving the health of coal miners.

3

Department of Labor 2014-2018 Strategic Plan Outreach,

www.dol.gov/sec/stratplan/2014outreach/.

This final rule is an important element in MSHA's Comprehensive Initiative to

END BLACK LUNG—ACT NOW!

Launched in December 2009, this initiative will significantly reduce disabling occupational lung disease in coal miners. It includes four components: Collaborative outreach, education and training, enhanced enforcement, and rulemaking. This final rule represents one aspect of MSHA's comprehensive and integrated approach to reduce and eliminate continued risks to miners from exposure to respirable coal mine dust. MSHA is committed to working with stakeholders to develop comprehensive outreach materials and to resolve any implementation issues. MSHA also intends to hold stakeholder seminars related to implementation of the final rule in locations accessible to the mining public.

Throughout the preamble, the terms “respirable coal mine dust”, “coal mine dust”, and “respirable dust” are used interchangeably.

This final rule combines the following rulemaking actions: (1) “Occupational Exposure to Coal Mine Dust (Lowering Exposure);” (2) “Verification of Underground Coal Mine Operators' Dust Control Plans and Compliance Sampling for Respirable Dust” (Plan Verification) (65 FR 42122, July 7, 2000, and 68 FR 10784, March 6, 2003); (3) “Determination of Concentration of Respirable Coal Mine Dust” (Single Sample) (65 FR 42068, July 7, 2000, and 68 FR 10940 March 6, 2003); and (4) “Respirable Coal Mine Dust: Continuous Personal Dust Monitor (CPDM)” (74 FR 52708, October 14, 2009). MSHA is withdrawing Plan Verification and Single Sample as separate rulemaking actions. However, the rulemaking records for the Plan Verification, Single Sample, and the CPDM rulemaking actions are incorporated into the rulemaking record for this final rule.

Several provisions in this final rule will singularly lower coal miners' exposure to respirable dust and reduce their risk of disease and disease progression. These provisions include lowering the respirable dust standards, using CPDMs for sampling, basing noncompliance determinations on MSHA inspectors' single shift sampling, full-shift sampling to account for occupational exposures greater than 8 hours per shift, changing the definition of normal production shift, changing the operator sampling program to require more sampling, requiring operator corrective action on one operator sample, and changes in the averaging method for operator samples to determine compliance. MSHA's quantitative risk assessment (QRA) in support of the final rule estimates the reduction in health risks when two provisions of the final rule are implemented—the final respirable dust standards and single shift sampling. The QRA shows that these two provisions would reduce the risks of CWP, severe

emphysema, and death from non-malignant respiratory disease (NMRD). The QRA projects, over a 45-year occupational lifetime, improvements in almost every underground job category and at least 6 surface categories. Large aggregated improvements are also projected for longwall tailgate operators and continuous mining machine operators (See the QRA discussion in Section III.B. of this preamble).

While the final 1.5 mg/m

3

and 0.5 mg/m

3

standards will reduce the risk of impairment, disease, and premature death, MSHA's QRA estimates remaining risk at the final standard. It is important to note that other provisions of this comprehensive and integrated final rule (e.g., use of CPDMs for sampling, changes in the definition of normal production shift, sampling for a full shift, changes in the sampling program, requiring operator corrective action on one operator sample, and changes in the averaging method to determine compliance on operator samples) will reduce these risks. The impacts of these other final provisions were not considered in the QRA. MSHA expects the final provisions, implemented in a comprehensive and integrated manner, will reduce the continued risks that miners face from exposure to respirable coal mine dust and would further protect them from the debilitating effects of occupational respiratory disease.

A. MSHA's Existing Respirable Dust Standards

MSHA's existing respirable dust standards, promulgated on April 8, 1980 (45 FR 23990) under Section 101 of the Mine Act, superseded Section 202(b) of the Mine Act. The standards require coal mine operators to continuously maintain the average concentration of respirable dust to which each miner is exposed during each shift at or below 2.0 milligrams per cubic meter of air (2.0 mg/m

3

) (30 CFR 70.100, underground coal mines; and 71.100, surface coal mines and surface areas of underground coal mines). Miners who have evidence of pneumoconiosis and are employed at underground coal mines or surface work areas of underground coal mines have the option to work in areas where average respirable dust concentrations do not exceed 1.0 mg/m

3

of air (30 CFR 90.100, part 90 miners). There is no separate standard for respirable silica; rather, where the respirable coal mine dust contains more than five percent quartz, the respirable coal mine dust standard is computed by dividing the percentage of quartz into the number 10 (30 CFR 70.101 (underground coal mines), § 71.101 (surface coal mines and surface areas of underground coal mines), and § 90.101 (part 90 miners)).

Under MSHA's existing standards, mine operators are required to collect bimonthly respirable dust samples and submit them to MSHA for analysis to determine compliance with respirable dust standards (compliance samples). If compliance samples do not meet the requirements of the dust standard, MSHA issues a citation for a violation of the standard and the operator is required to take corrective action to lower the respirable dust concentration to meet the standard. Further, the operator must collect additional respirable dust samples during the time established for abatement of the hazard or violation (abatement sampling).

Underground coal mine operators collect and submit two types of samples during bimonthly sampling periods: (1) “Designated occupation” (DO) samples taken for the occupations exposed to the greatest concentrations of respirable dust in each mechanized mining unit (§ 70.207); and (2) “designated area” (DA) samples collected at locations appropriate to best measure concentrations of respirable dust associated with dust generation sources in the active workings of the mine (§ 70.208). The operator's approved ventilation and methane and dust control plan, required in existing § 75.370, must show the specific locations in the mine designated for taking the DA samples. In addition, mine operators take respirable dust samples for part 90 miners (§§ 90.207 and 90.208).

For surface work areas of underground mines and for surface mines, mine operators are required to collect bimonthly samples from “designated work positions” (DWPs), which are designated by the District Manager (§ 71.208).

Compliance determinations are based on the average concentration of respirable dust measured by five valid respirable dust samples taken by the operator during five consecutive normal production shifts or five normal production shifts worked on consecutive days (multiple-shift samples). Compliance determinations are also based on the average of multiple measurements taken by the MSHA inspector over a single shift (multiple, single-shift samples) or on the average of multiple measurements obtained for the same occupation on multiple days (multiple-shift samples).

Under the existing program, sampling results are often not known to mine operators, miners, and MSHA for at least a week or more after the samples are collected. Due to the delay in receiving sampling results, operators are unable to take timely corrective action to lower dust levels when there are overexposures.

B. 1992 Coal Mine Respirable Dust Task Group Report, 1995 NIOSH Criteria Document, and 1996 Dust Advisory Committee Report

In May 1991, the Secretary directed MSHA to conduct a review of the coal mine respirable dust control program and to develop recommendations on how the program could be improved. MSHA established an interagency task group (Task Group) which published their findings and recommendations in the June 1992, Review of the Program to Control Respirable Coal Mine Dust in the United States. The Task Group Report can be accessed electronically at

http://www.regulations.gov/#!documentDetail;D=MSHA-2010-0007-0211.

On November 7, 1995, NIOSH submitted to the Secretary a criteria document recommending reduced standards for respirable coal mine dust and crystalline silica. On April 25, 1996, MSHA published a

Federal Register

notice (61 FR 18308) stating that it had decided to respond to the 1995 NIOSH Criteria Document by developing a proposed rule “derived from the recommendations” in the NIOSH Criteria Document. MSHA further stated that, although it would begin “the background work necessary to develop such a rule,” it would defer development of the rule until it received a report from the Secretary of Labor's Advisory Committee on the Elimination of Pneumoconiosis Among Coal Mine Workers (Dust Advisory Committee), which the Secretary had established on January 31, 1995, and to which MSHA had referred the NIOSH criteria document. One of the NIOSH recommendations in the Criteria Document was to use single, full-shift samples to compare miners' exposures with the NIOSH recommended exposure limit. The NIOSH Criteria Document can be accessed electronically at

http://www.cdc.gov/niosh/docs/95-106/.

On November 14, 1996, the Dust Advisory Committee submitted its report to the Secretary. The Dust Advisory Committee Report can be accessed electronically at

http://www.msha.gov/S&HINFO/BlackLung/1996Dust%20AdvisoryReport.pdf.

The report contained 20 wide-ranging principal recommendations, subdivided into approximately 100 action items, aimed at eliminating coal miners' pneumoconiosis and silicosis. The report recommended that MSHA consider lowering the level of allowable

exposure to coal mine dust, with any reduction accompanied by a phase-in period to allow allocation of sufficient resources to the compliance effort. The report also recommended that MSHA should change the compliance sampling program to allow use of single, full-shift samples for determining compliance. On January 24, 1997, MSHA published a

Federal Register

notice (62 FR 3717) responding to the 1996 Dust Advisory Committee Report. In the response, MSHA stated its intent to conduct an in-depth evaluation of the recommendations and respond to them.

C. 2000 and 2003 Plan Verification Proposed Rules

On July 7, 2000, MSHA published the Plan Verification proposed rule (65 FR 42122, July 7, 2000). The proposal would have required underground mine operators to have a verified mine ventilation plan, with MSHA collecting samples to verify the adequacy of dust control parameters specified in the ventilation plan to maintain respirable dust standards (“verification sampling”).

In response to comments urging MSHA to withdraw the proposal, MSHA published a new proposed rule on March 6, 2003, (68 FR 10784), which would have required mine operators to have a “verified” mine ventilation plan and conduct verification sampling on each mechanized mining unit (MMU). Under the proposal, mine operators would have to demonstrate the adequacy of dust control parameters specified in the ventilation plan to maintain the concentration of respirable coal mine dust and quartz at or below dust standards. In addition, the mine operators' existing bimonthly respirable dust sampling program for each MMU and DA would have been eliminated and MSHA would have assumed responsibility for compliance and abatement sampling in underground coal mines.

The 2003 proposal would have also provided for the use of CPDMs once the CPDM was verified as reliable under mining conditions and commercially available.

Public hearings were held in May 2003. The closing date for the comment period for the Plan Verification proposed rule was extended indefinitely to obtain information concerning CPDMs being tested by NIOSH (68 FR 39881, July 3, 2003).

The following provisions from the 2003 Plan Verification proposal have been revised and integrated into this final rule: (1) Use of the CPDM in monitoring respirable dust exposures; (2) recording the amount of material produced by each MMU during each production shift and retaining the record; (3) sampling for respirable dust during the entire time that a miner works to account for shifts longer than 8 hours; (4) requiring that dust control parameters in the mine's ventilation plan be revised when respirable dust overexposures are indicated; and (5) threshold values that would be used to determine violations based on single sample measurements.

D. 2000 Single Sample Proposed Rule

On July 7, 2000, MSHA and NIOSH jointly published a proposed rule on Determination of Concentration of Respirable Coal Mine Dust (Single Sample) (65 FR 42068). The proposal would have rescinded the 1972 Joint Finding and established that a single, full-shift measurement of respirable coal mine dust may be used to determine the average concentration on a shift if that measurement accurately represents atmospheric conditions to which a miner is exposed during such shift.

MSHA proposed the 2000 Single Sample rule following the 11th Circuit Court of Appeals decision in

National Mining Association (NMA) et al.

v.

Secretary of Labor, et al.,

153 F.3d 1264 (11th Cir. 1998). In this case, the Court reviewed the 1998 Final Joint Notice of Finding issued by MSHA and NIOSH. The 1998 Final Joint Finding, issued on February 3, 1998, concluded that the 1972 Joint Finding was incorrect and stated that the average respirable dust concentration to which a miner is exposed can be accurately measured over a single shift (63 FR 5664). The Court vacated the 1998 Joint Finding on procedural grounds. It found that MSHA was required by section 101(a)(6)(A) of the Mine Act to engage in rulemaking and demonstrate that a single, full-shift measurement adequately assures that no miner will suffer a material impairment of health, on the basis of the best available evidence; uses the latest available scientific data in the field; is technologically and economically feasible; and is based on experience gained under the Mine Act and other health and safety laws (153 F.3d at 1268-1269).

On March 6, 2003, MSHA and NIOSH reopened the rulemaking record to allow further comment on the Single Sample rulemaking and to solicit comment on new data and information added to the record (68 FR 10940). In May 2003, joint public hearings were held on the 2000 Single Sample proposal and the 2003 Plan Verification proposal. The comment period for the Single Sample proposal was extended indefinitely in order to obtain information on CPDMs being tested by NIOSH (68 FR 47886, August 12, 2003). The Single Sample proposal is integrated into and a part of this final rule, which permits MSHA inspectors to use single, full-shift samples to determine compliance with the respirable dust standard.

E. Continuous Personal Dust Monitor (CPDM)

On April 6, 2010 (75 FR 17512), MSHA and NIOSH published a final rule, effective June 7, 2010, revising approval requirements under 30 CFR part 74 for the existing coal mine dust personal samplers. It also established new approval requirements for the CPDM.

The CPDM is new technology that provides a direct measurement of respirable dust in the miner's work atmosphere on a real-time basis. In September 2006, NIOSH published the results of a collaborative study designed to verify the performance of the pre-commercial CPDM in laboratory and underground coal mine environments. According to the NIOSH Report of Investigations 9669, “Laboratory and Field Performance of a Continuously Measuring Personal Respirable Dust Monitor,” (Volkwein et al., U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health (USDHHS, CDC, NIOSH) 2006), the CPDM is accurate, precise, and durable under harsh mining conditions in providing continuous exposure information previously not available to coal miners and coal mine operators.

On October 14, 2009, MSHA published a Request for Information (RFI) on potential applications of CPDM technology to monitor and control miners' exposure to respirable coal mine dust during a work shift (74 FR 52708). The comment period closed on December 14, 2009.

On September 6, 2011, NIOSH approved a commercial CPDM as meeting the CPDM requirements of 30 CFR part 74 (USDHHS, CDC, NIOSH, 2011).

F. Regulatory History of This Final Rule

On October 19, 2010, MSHA published a proposed rule, Lowering Miners' Exposure to Respirable Coal Mine Dust, Including Continuous Personal Dust Monitors (75 FR 64412). The comment period was scheduled to close on February 28, 2011. The QRA in support of the proposal and Preliminary Regulatory Economic Analysis (PREA) were made publicly available at that time.

On October 20, 2010, MSHA held a meeting at MSHA Headquarters in Arlington, Virginia, and via conference call to brief interested stakeholders on the proposed rule.

On November 15, 2010, MSHA published a Notice scheduling six public hearings on the proposed rule in locations accessible to the mining public (75 FR 69617). In response to requests from the public, two of the hearings were rescheduled and an additional hearing was added, for a total of seven, to provide a maximum opportunity for public participation in the rulemaking (75 FR 73995). Hearings were held: December 7, 2010, in Beckley, WV; January 11, 2011, in Evansville, IN; January 13, 2011, in Birmingham, AL; January 25, 2011, in Salt Lake City, UT; February 8, 2011, in Washington, PA; February 10, 2011, in Prestonsburg, KY; and February 15, 2011, in Arlington, VA.

On January 14, 2011, MSHA extended the comment period from February 28, 2011 to May 2, 2011 (76 FR 2617). On May 4, 2011, MSHA again extended the comment period to May 31, 2011 (76 FR 25277). On May 27, 2011, MSHA extended the comment period to June 20, 2011 (76 FR 30878).

On March 8, 2011, MSHA published a

Federal Register

notice (76 FR 12648) requesting comment on information that was included in the preamble to the proposed rule and other issues that were raised during the public hearings. The notice requested comment on 25 specific issues and included two clarifications.

Public comments and supporting documentation submitted were posted on the MSHA Web site and on

www.regulations.gov

, along with transcripts and exhibits from the public hearings.

Several commenters, referring to an MSHA response to a request for documents under the Freedom of Information Act (FOIA), stated that they were denied access to documents that were critical to a thorough evaluation of the proposed rule. The request involved documents specifically related to the QRA in support of the proposed rule, and documents generally related to the rulemaking.

All documents that were critical to a thorough evaluation of the proposed and final rules are in the rulemaking record, and posted on MSHA's Web site and on

www.regulations.gov

, as noted above. These publicly available documents include Agency materials considered in the development of the proposed and final rules, public comments and supporting documentation submitted, along with transcripts and exhibits from the public hearings. If materials included in the docket are copyrighted, they are listed on

www.regulations.gov

but are not reproduced there. MSHA also posted additional historical information and data on respirable coal mine dust on its Web site at the request of the public. MSHA's complete rulemaking docket, including studies, articles, and reports reviewed by MSHA in the development of the proposed and final rules, is available in hard copy for inspection at its headquarters office. Peer reviewed documents of the QRA for the proposed rule prepared by NIOSH and the Occupational Safety and Health Administration (OSHA) at MSHA's request, as well as the QRA for the proposed rule, have been available on the Black Lung Single Source Page on MSHA's Web site since the October 19, 2010 publication of the proposed rule at

http://www.msha.gov/S&HINFO/BlackLung/Homepage2009.asp

.

G. Government Accountability Office Activities

The Consolidated Appropriations Act, 2012, required that the Government Accountability Office (GAO) review and report on the data collection, sampling methods, and analyses MSHA used to support its proposal. In August 2012, GAO issued a report, “

Mine Safety: Reports and Key Studies Support the Scientific Conclusions Underlying the Proposed Exposure Limit for Respirable Coal Mine Dust”,

which assessed the strengths and limitations of the data and the analytical methods MSHA used to support its proposal to lower the exposure limit for respirable coal mine dust. GAO concluded that the evidence MSHA used did support its conclusion that lowering the limit as proposed would reduce miners' risk of disease.

In May 2013, GAO was requested to conduct an additional analysis on MSHA's proposed rule. In April 2014, GAO issued a report, “

Basis for Proposed Exposure Limit on Respirable Coal Mine Dust and Possible Approaches for Lowering Dust Levels”.

GAO examined (1) the extent to which MSHA used recent CWP trend data as a basis for its proposed exposure limit, and (2) expert views on ways to lower the dust levels in coal mines, including their associated advantages, disadvantages, and cost. In the report, GAO concluded that MSHA appropriately did not use recent trend data on CWP as a basis for its proposal to lower the permissible exposure limit for respirable coal mine dust. According to GAO, these recent data from NIOSH were inappropriate for this purpose because they do not include the types of detailed information about individual miners needed to estimate the likelihood that miners would develop CWP at different exposure levels, such as historical dust exposures. With the help of the National Academies, GAO convened a group of experts knowledgeable about underground coal mining and methods for reducing coal mine dust. GAO did not make any recommendations in this report. MSHA has reviewed both GAO reports and has determined that no further action is necessary.

MSHA has also reviewed the explanatory statement by the Chairman of the House Committee on Appropriations in the 2014 Appropriations Act regarding the coal mine dust rule. Consistent with the explanatory statement, MSHA has taken into consideration all relevant information and conclusions from the GAO study when addressing compliance assistance, training, or post-implementation needs in connection with the final rule. MSHA also considered all available technologies and work practices that would allow mine operators to reduce miners' exposures to respirable coal mine dust in a manner that is not economically prohibitive for the long-term viability of the affected mines, while reducing miners' exposure to respirable (coal) mine dust. (MSHA discusses feasibility in section III.C. of this preamble and in chapter IV of the REA.) MSHA intends to develop outreach materials related to implementation of the final rule and hold stakeholder seminars in locations accessible to the mining public. MSHA also intends to develop compliance assistance materials to ensure that operators have a sufficient number of certified persons to perform sampling and maintenance and calibration of CPDMs.

III. Discussion of the Final Rule

A. Health Effects

The health effects from occupational exposure to respirable coal mine dust consist of interstitial and obstructive pulmonary diseases. Miners develop Coal Workers' Pneumoconiosis (CWP) or nonmalignant respiratory disease (NMRD). There are no specific treatments to cure CWP or NMRD. These chronic effects may progress even after miners are no longer exposed to respirable coal mine dust resulting in increased disability and death. Other complications may follow, such as pulmonary and cardiac failure, that result in total disability and premature death.

The health effects from occupational exposure to respirable coal mine dust were discussed in the preamble to MSHA's proposed rule on Plan Verification published on March 6, 2003 (68 FR 10784). The literature referenced in that document pre-dated 1999. More recent literature, from 1997 to mid-2009 with occasional references to earlier papers, was discussed in the Health Effects section of the preamble to the proposed rule for this final rule (75 FR 64412, 64458).

Reduction of coal mine dust exposure is the only effective way to prevent either CWP or NMRD. Screening and surveillance programs detect trends and clusters of disease occurrences and allow secondary preventive intervention to slow the rate of progression in miners. Data from screening and surveillance programs provide estimates of the prevalence of occupational respiratory disease among working coal miners.

At the existing respirable coal mine dust standard of 2.0 mg/m

3

, cases of CWP and NMRD continue to occur. In recent years, the prevalence of CWP has increased among experienced miners, and in some cases, CWP has progressed rapidly to the more advanced form-progressive massive fibrosis (PMF). The persistence of disease requires that additional action be taken to reduce coal mine dust exposures. The final rule will reduce occupational pulmonary disease, disability, and premature mortality in coal miners.

Although not a basis or rationale for the final rule, in May 2011, CWP prevalence in a West Virginia mining population was reported in the Governor's Independent Investigation into the April 5, 2010, explosion at the Upper Big Branch (UBB) mine in southern West Virginia (p. 32). This investigation reported the prevalence of CWP as determined by autopsies in the 29 miners who died. Twenty-four of the 29 miners had sufficient lung tissue available to make a determination relating to CWP. Prevalence of CWP in these 24 miners was 71 percent (17 of 24 miners), which compares with the national prevalence rate for CWP among active underground miners of 3.2 percent, and the prevalence rate in West Virginia of 7.6 percent. The ages of the UBB miners with CWP ranged from 25 to 61 years. Of the 7 miners who were not identified as having CWP, 4 had what was characterized as “anthracosis” on their autopsy reports. This term is often used in lieu of the term pneumoconiosis, or may refer to a black pigment deposition without the fibrosis and other characteristics needed to make a firm diagnosis of pneumoconiosis. Three of the 24 miners had no pneumoconiosis or anthracosis noted.

Of the 17 UBB miners with CWP, 5 had less than 10 years of experience as coal miners, while 9 had more than 30 years of coal mining experience. At least 4 of the 17 worked almost exclusively at UBB. All but 1 of the 17 with CWP began working in the mines after the 2.0 mg/m

3

respirable coal mine dust standard became effective in 1973.

There was support for the proposed rule from many commenters who agreed with MSHA's conclusions in the health effects and QRA discussions in the preamble to the proposed rule. Commenters supported the proposed rule which would lower the existing dust standards, require the use of continuous personal dust monitors (CPDMs), base compliance determinations on single, full-shift samples, address extended work shifts, redefine a normal production shift, and extend medical screening and surveillance. These commenters stated that there has been an alarming increase of CWP within the past 10 years and that MSHA's existing standards have not succeeded in eliminating Black Lung.

Other commenters stated that the proposed rule is not needed. Some stated that MSHA should better enforce its existing standards rather than propose new standards. Some stated that black lung rates have been declining since 2000 when MSHA and NIOSH began using enhanced surveillance methods and that the Agency used selective data to support the proposed reduction in the standard. Others stated that MSHA should only address the health concerns in particular areas of the country, which include Virginia, West Virginia, and Kentucky. Several commenters stated that the proposal is not based on the best available evidence but, rather, is based on faulty science and medical data. One commenter suggested that MSHA, NIOSH, industry, and labor conduct a nationwide study using the CPDM to determine what dust concentrations are protective and achievable. The comments are discussed below.

In the health effects section of the proposed rule, MSHA reported results from NIOSH publications and studies that were based on grouped surveillance data. In response to commenters requesting that the underlying demographic information be made available, MSHA points out that these results are part of NIOSH's coal miner surveillance data included in the proposed rule's hazard and risk assessment analyses. NIOSH posts summary surveillance data on U.S. coal miners on its Web site at

http://www.cdc.gov/niosh/topics/surveillance/ords/

. These data are generated based on the requirements of 42 CFR part 37, Specifications for Medical Examinations of Underground Coal Miners. Because of privacy protection laws, such as the Health Insurance Portability and Accountability Act (HIPAA) of 1996, the Privacy Act of 1974, and the Freedom of Information Act, MSHA cannot provide underlying personal identifying information.

Some commenters stated that the proposed rule was based on three data sources: The NIOSH 1995 Criteria Document, a literature update by NIOSH entitled “Current Intelligence Bulletin 64, Coal Mine Dust Exposure and Associated Health Outcomes, A Review of Information Published Since 1995” (“NIOSH CIB 64”) (USDHHS, CDC, NIOSH (2011a)), and various NIOSH papers on its enhanced surveillance studies. MSHA did not use the NIOSH literature update in the development of the proposed rule because it was published in April 2011 and, therefore, not final when the proposed rule was published on October 19, 2010. However, the NIOSH CIB 64 provides supplementary information that supports the final rule and is referenced later in this section of the preamble. NIOSH submitted CIB 64 to MSHA during the comment period for the proposed rule.

Some commenters stated that MSHA did not produce for independent analysis the underlying data from the NIOSH Criteria Document and X-ray program. One commenter stated that this is a violation of the Office of Management and Budget (OMB) and MSHA guidelines on data quality which prevented stakeholders from being able to comment on the scientific basis of the proposed rule.

The Data Quality Act or Information Quality Act directs OMB to issue guidelines to agencies to ensure and maximize the quality, objectivity, utility, and integrity of information that agencies maintain and disseminate (Section 515 of the Treasury and General Government Appropriations Act for FY 2001 (Pub. L. 106-554)). MSHA has satisfied the requirements of OMB's 2002 data quality Guidelines, for Ensuring and Maximizing the Quality, Objectivity, Utility, and Integrity of Information Disseminated by Federal Agencies (36 FR 8452, February 22, 2002). MSHA has adopted well-established quality assurance techniques to ensure the quality of information disseminated. Information

is subject to internal agency quality control and audit, and any appropriate Department of Labor level review before being disseminated to the public. MSHA's Information Quality Guidelines are available on the Agency's Web site at:

http://www.msha.gov/infoquality/mshainfoquality.htm

.

MSHA explained in the preamble to the proposed rule that the proposal was developed in part on the recommendations in the 1995 NIOSH Criteria Document. NIOSH is the agency in possession of the underlying data associated with the Criteria Document and has posted data relevant to the Criteria Document on its Web site at

http://www.cdc.gov/niosh/topics/surveillance/ords/

. In accordance with Section 101(a) of the Mine Act, NIOSH submitted the Criteria Document to the Secretary of Labor for consideration in developing standards to reduce health risks associated with miners' exposure to respirable dust.

In addition, the Health Effects section in the preamble to the proposed rule contains a comprehensive inventory and summarizes key aspects of scientific literature and studies on the health effects from occupational exposure to respirable coal mine dust. Regarding the NIOSH X-ray data, NIOSH posts summary surveillance data on U.S. coal miners on the Web site previously noted at

http://www.cdc.gov/niosh/topics/surveillance/ords/

.

One commenter stated that using data from the NIOSH surveillance program violates the data quality guidelines because NIOSH self-selects the program participants and therefore the data is biased. The commenter also stated that data from the B-reader program is imprecise, inaccurate and biased because the B-reader program gives significant false-positive readings thereby exaggerating the incidence of CWP.

The relatively low participation rates, potential self-selection biases, and a lack of correspondent exposure histories for the individual miners involved limit the use of the NIOSH surveillance data as support for the Quantitative Risk Assessments. Additional discussion is included in Section III.B., Quantitative Risk Assessment, of the preamble. NIOSH instituted the B-reader program to ensure competency and consistency in radiographic reading by evaluating the ability of readers to classify a test set of radiographs. A discussion of NIOSH's B-reader program is included in Section III.A., Health Effects, of the preamble.

In developing the proposed rule, MSHA evaluated over 150 peer-reviewed papers as part of the Agency's health effects assessment (75 FR 64460, October 19, 2010), in addition to the data from MSHA's proposed rule on Plan Verification. The literature review focused on studies of morbidity and mortality among coal miners in many countries, including the United States, South Africa, Europe, Britain, China, Australia, Turkey, and Japan. This research evaluated the relationship between respirable coal mine dust exposure and the respiratory disease it causes. The research reported on the etiology of adverse respiratory diseases, including CWP, PMF, and NMRD, such as chronic obstructive pulmonary disease (COPD) and emphysema. The fact that similar results have been found in decades of research, covering a wide variety of populations at various respirable coal mine dust exposure levels and working conditions, supports the determination that exposure to respirable coal mine dust is a significant causal factor in the development of respiratory diseases in coal miners. The conclusion of MSHA's review of this research and of NIOSH's 2011 literature update is that chronic coal mine dust exposure causes respiratory health effects including CWP, PMF, COPD, and emphysema.

Recognition that long-term respirable coal dust exposure causes irreversible respiratory health effects has been accepted by the medical community for decades. On March 26, 1969, Charles C. Johnson, Jr., Administrator, Consumer Protection and Environmental Health Service, Public Health Service, U.S. Department of Health, Education, and Welfare, testified before the General Subcommittee on Labor, and presented remarks of the Surgeon General addressing the level of medical understanding about the etiology of CWP at that time.

4

Johnson testified that CWP is a chronic chest disease caused by the accumulation of fine coal mine dust particles in the human lung that, in its advanced forms, leads to severe disability and premature death.

4

91st Congress House of Representatives Report, 1st Session No. 91-563, Federal Coal Mine Health and Safety Act, October 13, 1969.

Johnson's testimony also pointed out that, by 1969, medical researchers in both Britain and the United States had repeatedly shown that coal miners suffer from more respiratory impairment and respiratory disability than the general population. These respiratory problems were frequently accentuated by chronic bronchitis and emphysema.

Estimates of the severity of disease risk at that time were derived from British research. This research provided the only quantitative exposure-response relationship available in 1969 and supported lowering the respirable coal mine dust standard from 3.0 mg/m

3

to 2.0 mg/m

3

. Adoption of the 2.0 mg/m

3

standard was believed to be protective against the risk of disability and premature mortality that accompanies PMF. However, NIOSH has noted that as more research was completed over the next 25 years, this assumption turned out to be inaccurate (NIOSH CIB 64, 2011a).

In 1995, NIOSH published “Criteria for a Recommended Standard—Occupational Exposure to Respirable Coal Mine Dust”, an analysis of research up through the early 1990s that further investigated the etiology of CWP and other adverse health effects associated with respirable coal mine dust exposure. NIOSH recommended that the federal coal mine dust limit be reduced to 1.0 mg/m

3

. This recommendation was based on risk estimates of CWP derived from two NIOSH studies of U.S. coal miners. Predictions were derived from each study for a working lifetime of 45 years at two exposure levels: 2.0 mg/m

3

and 1.0 mg/m

3

. The recommendation was also based on information that predicted excess lung function decrements following working lifetime exposures to 2.0 mg/m

3

and 1.0 mg/m

3

respirable coal mine dust. NIOSH also evaluated information from other epidemiologic studies in reaching its 1995 recommendations. NIOSH estimated, and MSHA concurs, that miners exposed to respirable coal mine dust at the existing 2.0 mg/m

3

standard are at significant risk of developing adverse health effects, such as CWP and NMRD, including COPD and emphysema.

Some commenters disagreed with NIOSH surveillance and research results as the basis for the proposed rule. These commenters stated that the prevalence of CWP and PMF in U.S. coal miners was overstated, surveillance was incomplete, and the 1.0 mg/m

3

standard was not justified. They presented various analyses of the NIOSH studies and submitted for the rulemaking record a NIOSH study that was published after the proposed rule (Suarthana et al., 2011). The Suarthana study is discussed in this Health Effects section of the preamble.

Some commenters suggested that MSHA should collect data from a representative or mandatory surveillance program and study the data in a scientifically sound manner to better understand the incidence of CWP.

MSHA believes that this program already exists in the National Coal Workers Health Surveillance Program (NCWHSP, also known as CWHSP) that is administered by NIOSH. MSHA has

used data generated from this program in the development of both the proposed and final rules.

Occupational health surveillance tracks occupational injuries, illnesses, hazards, and exposures to improve worker safety and health and to monitor trends and progress over time. Surveillance includes both population- or group-based activities and individual or case-based activities. Worker screening and monitoring detects early disease in high-risk individuals.

The purpose of federal and state surveillance programs for chronic lung diseases, such as CWP, PMF, and NMRD, is to identify not only cases of disease, but also conditions under which the cases develop in order to improve disease control and prevention. There are three levels of prevention. Primary prevention in the case of dust-related lung disease includes reducing exposure to dust, generally through engineering controls. Secondary prevention focuses on early detection of disease and intervention in order to slow or eliminate progression. Much of the medical surveillance conducted by NIOSH is secondary prevention. Tertiary prevention involves miners seeking further medical care only after they have symptoms, progression to later stages is more likely, and the primary treatment is to manage symptoms of disease since it is too late to prevent disease.

There is a spectrum of respiratory disease development in coal miners exposed to respirable coal mine dust. Pathologic changes occur during the subclinical stage of disease development that are not detectable by either spirometry or chest x-ray (CWP 0/0). For this reason, all miners should have an initial medical examination to establish a baseline health status on which future medical surveillance can be compared to determine disease presence or progression. NIOSH and many of the research papers on which the proposed health effects assessment was based use CWP 1/0+ as the category where disease progression is evident; many of these miners may not have overt symptoms, but the chest x-ray shows signs of fibrotic changes. The use of this CWP category as a sign of the development of minimal illness dates from the 1969 Coal Act, where the Surgeon General recommended that miners be removed from dusty environments as soon as they showed “minimal effects” of dust exposure on chest-x-ray, i.e., pinpoint, dispersed micro-nodular lesions. Many miners may also report symptoms of developing respiratory disease, such as chronic cough, phlegm production, wheezing, and shortness of breath.

Many comments focused only on detection of clinical disease (tertiary prevention), once disease has advanced well beyond the clinical horizon when symptoms appear (CWP category 2/0+). One commenter submitted an analysis of CWP mortality in a subgroup of miners with advanced disease at the CWP 2/0+ level. While this analysis may help to understand the etiology of advancing disease, it does not identify how the disease process begins or how to prevent disease from developing. Miners with this level of disease present pulmonary symptoms and are likely to suffer from disease progression.

The focus of federal coal workers' health surveillance programs is on prevention of clinical disease, not detection of disease that has progressed well beyond the clinical horizon. The Coal Workers' X-Ray Surveillance Program (CWXSP) was established under the Federal Coal Mine Health and Safety Act of 1969, as amended by Section 203(a) of the Mine Act (30 U.S.C. 843(a)). The CWXSP Program, which is part of the National Coal Workers Health Surveillance Program (NCWHSP), began in 1970. It is administered by NIOSH. The CWXSP provides all underground coal miners with periodic, x-ray examinations, at no cost to the miner, at least every five years (42 CFR part 37).

The National Coal Study (NCS) was a long-term epidemiologic study, limited to workers in a selected group of mines with various seam heights, mining methods, coal types, and geographic locations. Many of the published peer-reviewed epidemiological studies reported in the proposed rule's health effects section grew out of the NCS. Commenters suggested that many of NIOSH's studies were incomplete due to design or other limitations and suggested that a detailed, nationwide epidemiological study be conducted based on mandatory screening before any action to lower the respirable dust standard is initiated.

MSHA does not believe that a nationwide epidemiological study, based on mandatory screening, as suggested by the commenter is needed before regulatory action is taken be reduce the respirable dust standard. Underground coal miners in the United States have been studied since before the 1969 Coal Act by the Public Health Service and State health agencies. Those studies were the basis for the current surveillance programs in this country. Numerous pre-Coal Act studies and studies since that time have characterized the respiratory system's response to various levels of respirable coal mine dust, a known fibrogenic dust. Significant levels of adverse lung diseases are continuing to develop in coal miners who have been exposed to respirable coal mine dust at the current standard.

Some commenters stated that x-rays are insensitive for detecting CWP and that surveillance programs suffer from inconsistent reading of the x-rays.

Early changes due to CWP are frequently identifiable on a high quality chest x-ray before the miner seeks medical attention due to symptoms. NIOSH instituted the B-reader program to ensure competency and consistency in radiographic reading by evaluating the ability of readers to classify a test set of radiographs. This creates and maintains a pool of qualified readers having the skills and ability to provide consistent and accurate ILO classifications. B-readers must retest every 4 years to maintain their B-reader status. A reader who fails the retest must take and pass the original approval examination before the expiration of the 4-year approval period in order to retain B-reader status. The implementation of this program in the mid-1970s, the update of the program to adjust to the ILO guidelines in 1980, and the revised ILO guidelines in 2000 and 2011 ensure B-reader consistency in reading x-rays.

In order to preserve continuity and consistency in the classifications, the images used in reproducing the 2011 ILO version of the standard radiographs are identical to those used for the 1980 set of standard radiographs, aside from one image which demonstrates pleural abnormalities. The ILO did endeavor to improve image quality in the 2000 set by using advanced computer imaging techniques. The NIOSH CWXSP requires that readers submit classifications adhering to the 2011 Revised Edition of the Guidelines for the Use of the ILO International Classification of Radiographs of Pneumoconiosis. The sets of standard images used in the 2011 and 1980 classifications are nearly identical, and thus it is the individual reader's choice which of these two sets of standard radiographs to use. However, because the quality of the 2011 standard radiographs has been enhanced by the ILO Guidelines, NIOSH recommends that readers use the 2011 standard radiographs for classifying films for NIOSH programs and studies (

http://www.cdc.gov/niosh/topics/chestradiography/breader-info.html

).

Classifying films can be variable, especially in lower disease categories, with differences of opinion between B-readers and by the same B-reader at different times (Attfield et al., 2007; Naidoo et al., 2004). To account for this

variability, the ILO classification system allows readers to determine profusion severity by indicating the most likely category and also by indicating a neighboring category that might also be valid. For example, a score of 1/2 means the disease state is classified as category 1, but could also be considered category 2. Another means of compensating for variability is to have a panel of readers interpret films by consensus rather than using a single reader. When the ILO system is used for surveillance and screening purposes, it has been demonstrated to be a valid means for identifying trends and disease clusters (Attfield et al., 2007; Naidoo et al., 2004; NIOSH, 2008). The CWXSP uses a profusion score of 1/0+ as indicative of CWP development.

Section 203(a) of the Mine Act specifically requires that operators provide periodic chest x-ray examinations to underground coal miners, and such other tests as the Secretary of Health and Human Services deems necessary to supplement the x-rays (30 U.S.C. 843(a)). In addition to pneumoconiosis apparent on x-rays, miners are at increased risk for the development of COPD. Chest x-rays alone cannot provide a measure of airflow obstruction and, therefore, often miss important lung disease. Spirometry, a simple breathing test, is an additional component of the health assessment of miners that is particularly useful. NIOSH has recommended periodic medical history and spirometry tests for both surface and underground coal miners since 1995, to facilitate preventive actions, increase miners' participation in programs for early detection of disease, and improve the derivation of representative estimates of the burden, distribution, and determinants of occupational lung disease in relation to coal mining in the United States. Final § 72.100 requires spirometry testing of both underground and surface miners.

A few commenters stated that a recent study by Suarthana et al. (2011) states that dust exposure is a poor predictor of CWP prevalence.

In response, MSHA notes that dose-response relationships between cumulative dust exposure and cases of respiratory diseases have been studied by NIOSH as part of the National Coal Study. The Suarthana study stated that: “Epidemiological modeling of CWP prevalence and incidence undertaken on underground coal miners in the USA and elsewhere has shown that the main predictor of CWP is cumulative exposure to respirable coal mine dust.”

As stated previously, NIOSH studies the causes and consequences of coal-related respiratory disease and, in cooperation with MSHA, carries out a program for early detection of coal workers' pneumoconiosis. These activities are administered through the CWXSP.

In the early 2000s, MSHA with assistance from NIOSH piloted the Miners' Choice Program (MCP) to offer all coal miners the opportunity to participate in the CWXSP by having medical staff travel to mines or other areas to conduct medical surveillance of mining populations at no cost to the mine operator. The MCP used a mobile medical examination unit to bring the medical exams, including chest x-rays, to the miners in remote areas to provide early detection of dust-related pulmonary disease. MSHA wanted to determine the state of miner health because participation in the CWXSP decreased from the high of 100% in 1970 to 1974 to a low of 20.6% in 1990 to 1994 (Table III-2). MSHA found that participation rates increased to 25.5% in 1995 to 1999; 34.1% in 2000 to 2004; and 41.7% in 2005 to 2009. MSHA further found that as more miners were screened, the prevalence of CWP detected fluctuated. CWP was detected in 2.0% of the miners who were x-rayed from 1995 to 1999; 3.6% from 2000-2004; and 2.7% from 2005 to 2009 (Table III-1). Although commenters stated that this increase was not real, additional miner participation resulting from the enhanced surveillance identified more cases of CWP that otherwise would have gone undetected.

The Miners' Choice Program was expanded into the Enhanced Coal Workers' Health Surveillance Program (ECWHSP) in March 2006 by NIOSH to continue increasing miner participation by providing additional respiratory health evaluations to coal miners. The ECWHSP uses a mobile medical examination unit to bring the medical exams to the miners in the field to provide early detection of dust-related pulmonary disease and target additional areas for prevention. This program offers lung function testing in addition to chest x-rays as part of the medical examination and asks miners to fill out occupational and health surveys.

The National Coal Workers' Autopsy Study, which is part of the NCWHSP, provides autopsies of deceased coal miners at the request of miners' next-of-kin at no cost to the family. Autopsy results may help support a black lung benefit claim and also help scientists and medical doctors learn more about CWP. Doctors collect standardized lung specimens during autopsies to be used in ongoing scientific research as well as to provide information to the next-of-kin regarding the presence and extent of CWP in the lungs of the deceased miner. Because one basic reason for the post-mortem examination is research (both epidemiological and clinical), a minimum of essential information is collected regarding the deceased miner, including occupational history and smoking history. The data collected are used by scientists for research purposes in defining the diagnostic criteria for pneumoconiosis and in correlating pathologic changes with exposures and x-ray findings.

NIOSH reports overall prevalence of CWP 1/0+ across all MSHA districts, as well as a national prevalence (Table III-1). These numbers are based on the average number of miners employed per time period (1995-1999, 2000-2004, and 2005-2009) and the number x-rayed per time period. When more information is available from complete medical examination records, NIOSH refines the estimates as in the case with reporting CWP prevalence based on tenure, i.e., the length of time worked in coal mining (Table III-2).

During the 2005 to 2009 period, for example, over 18,500 active underground coal miners were screened as part of the CWXSP. As shown in Table III-1, this is approximately 42% of all active underground miners (NIOSH, 2011—Work-Related Lung Disease Surveillance System, CWXSP. ref. no. 2011T02-17, May 2011). Active miners from all MSHA districts participated in this screening.

Some commenters stated that the NIOSH surveillance programs are not “well-established scientific processes for data collection” and that black lung rates have declined since 2000.

NIOSH surveillance of CWP started in 1970 and continues today using the same case definition of CWP 1/0+ (Tables III-1 and III-2). The number of miners participating in the program has fluctuated through the years. NIOSH's active surveillance programs have reached additional miners, as shown in Table III-2; the percentage participating in the period from 2005 to 2009 was 41.7% as compared to a low of 20.6% in the period from 1990 to 1994. In addition, the number of underground coal miners in the United States has declined from over 150,000 in the 1975-1979 time period to under 45,000 in the 2005-2009 time period. The number of miners examined that provided tenure data on the health questionnaire forms was approximately 85,000 in the 1970-1974 time period to approximately 11,000 in the late 2000s.

Miners who stop working in mining are lost to follow-up. Since their health status is not known, surveillance of only

active miners may underestimate the prevalence of disease. Cohen et al. (2008) reported that disease progression continues after exposures stop, increasing lung function impairment and pneumoconiosis levels in miners once they leave employment (i.e., ex-miners and retired miners). Coal mine dust clearance from the lungs is slow and incomplete, allowing continued contact between the cytotoxic dust and lung tissues. This progression of disease after retirement from coal mining (i.e., after exposure ceased) was also observed in other countries (Cohen et al., 2008). Ex-miners displayed higher levels of respiratory disease than current miners illustrating the progression of CWP to PMF even after exposure ceased (Naidoo et al., 2005 and 2006). Miners with advanced disease are forced to retire because they can no longer perform mining tasks (Cohen et al., 2008).

Exposures, as estimated by MSHA inspector samples, have decreased since passage of the 1977 Mine Act from a mean of 0.796 mg/m

3

(with 18.7% of samples above the 2.0 mg/m

3

standard) in 1979 to 0.468 mg/m

3

(with 3.2% of samples above the 2.0 mg/m

3

standard) in 2003 at underground coal mines; and from 0.384 mg/m

3

(5.0% above the 2.0 mg/m

3

standard) in 1979 to 0.148 mg/m

3

(0.8% above the 2.0 mg/m

3

standard) in 2003 at surface coal mines (NIOSH, 2011—Work-Related Lung Disease Surveillance System, CWXSP. ref. no. 2007T02-14;

http://www2.cdc.gov/drds/WorldReportData/FigureTableDetails.asp?FigureTableID=529&GroupRefNumber=T02-14

). As exposures were reduced, the prevalence of CWP 1/0+ was also reduced, on average. Prevalence information on CWP 1/0+ among miners from the NCWHSP, reported on NIOSH's Web site, was 2.0% in the 1995-1999 time period; 3.6% in the 2000-2004 time period; and 2.7% in the 2005-2009 time period (Table III-1). When tenure is considered, however, the prevalence increased to 2.6%, 4.1%, and 4.1%, respectively (Table III-2). Table III-2 shows that disease progression continues even after exposures were reduced.

ER01MY14.000

“−” indicates fewer than five miners examined or with CWP (to protect identification of miners screened who have been diagnosed with disease because of privacy laws).

Note:

The average number employed during the period, based upon quarterly reports by coal mine operators to MSHA. Because of hiring and layoffs, the total number of individuals who worked at underground mines in any period may exceed the average employment.

Source:

CWP data from NIOSH's CWXSP. Coal District codes from MSHA.

http://www2a.cdc.gov/drds/WorldReportData/FigureTableDetails.asp?FigureTableID=2551&GroupRefNumber=T02-17.

Table III-2—CWXSP: Number and Percentage of Examined Underground Miners With CWP (ILO Category 1/0+) by Tenure Information Provided on Medical Questionnaire, 1970-2009

Time Period

1970-1974

1975-1979

1980-1984

1985-1989

1990-1994

1995-1999

2000-2004

2005-2009

*

Average No. Employed at Underground Mines

104,705

150,475

131,113

91,122

69,424

50,319

39,544

44,546

Number of X-rays

105,841

99,610

45,797

19,049

14,283

12,674

16,644

18,563

% of Miners X-rayed

101.1

66.2

34.9

20.9

20.6

25.2

42.1

41.7

% of Miners X-rayed That Reported Tenure Information

80.9

59.1

78.1

67.3

82.1

71.8

82.9

60.4

Tenure (years in underground mining)

Total No. of Miners Examined

85,644

58,864

35,787

12,816

11,727

9,100

13,794

11,211

Total No. with CWP

13,288

2,887

1,083

460

424

233

570

455

Total % with CWP

15.5

4.9

3

3.6

3.6

2.6

4.1

4.1

0-9

No. of Miners Examined

36,303

43,296

23,190

5,063

1,638

806

4,261

4,281

No. with CWP

803

475

186

44

20

7

47

27

% with CWP

2.21

1.1

0.8

0.9

1.2

0.9

1.1

0.6

10-14

No. of Miners Examined

6,464

5,460

7,050

4,345

2,968

642

562

311

No. with CWP

586

328

166

111

68

7

10

**

% with CWP

9.1

6

2.4

2.6

2.3

1.1

1.8

1

15-19

No. of Miners Examined

6,210

2,705

2,253

2,071

4,037

1,778

1,156

235

No. with CWP

910

298

139

118

125

34

37

5

% with CWP

14.7

11

6.2

5.7

3.1

1.9

3.2

2.1

20-24

No. of Miners Examined

8,769

2,044

993

683

2,178

3,475

3,100

958

No. with CWP

1877

380

102

63

115

86

152

47

% with CWP

21.4

18.6

10.3

9.2

5.3

2.5

4.9

4.9

25+

No. of Miners Examined

27,898

5,359

2,301

654

906

2,399

4,715

5,426

No. with CWP

9,112

1,406

490

124

96

99

324

376

% with CWP

32.7

26.2

21.3

19

10.6

4.1

6.9

6.9

*

Number from Table III-1, 2005-2009 number of miners X-rayed.

**

Indicates fewer than 5 miners with CWP.

Source: CWP data from NIOSH's Coal Workers' X-ray Surveillance Program (CWXSP). Ref. No. 2007F02-06, 2011T02-12.

Some commenters stated that the prevalence of disease was overstated in the proposed rule. Annual prevalence data are reported on NIOSH's Web site and summarized in Table III-3 for 1970 through 2009. Prevalence in 1970, the first year of surveillance, was 2,162 cases (30.5%). The respirable dust standard at the time was 3.0 mg/m

3

. As shown in Table III-3, the percent of miners show a downward trend until after 1999. In the last decade, the observed prevalence of CWP 1+ in examined miners has varied from a low of 46 cases (2.6%) in 2004 to 167 cases (5.8%) in 2006. The number of miners examined in 2005 was only 706 miners; 37 of them, or 5.2%, were diagnosed with CWP 1/0+. In comparison in 2000, 6,264 miners were examined and 242 (3.9%) were diagnosed with CWP 1/0+.

Table III-3—CWXSP: Number and Percentage of Examined Underground Miners (Who Provided Tenure Information) With Coal Workers' Pneumoconiosis (ILO Category 1/0+) Yearly Totals, 1970-2009, (Using Data From Table III-2)

Year

Total No. of

Miners

Examined

Total No. with CWP

Total % with CWP

1970

7,085

2,162

30.5

1971

30,703

5,154

16.8

1972

6,916

717

10.4

1973

8,001

961

12.0

1974

32,939

4,294

13.0

1970-1974

85,644

13,288

15.5

1975

8,779

482

5.5

1976

7,581

174

2.3

1977

7,870

194

2.5

1978

10,235

386

3.8

1979

24,399

1,651

6.8

1975-1979

58,864

2,887

4.9

1980

7,532

303

4.0

1981

9,201

234

2.5

1982

4,536

80

1.8

1983

4,833

133

2.8

1984

9,685

333

3.4

1980-1984

35,787

1,083

3.0

1985

3,056

69

2.3

1986

848

30

3.5

1987

2,867

92

3.2

1988

3,589

168

4.7

1989

2,456

101

4.1

1985-1989

12,816

460

3.6

1990

891

61

6.8

1991

1,036

38

3.7

1992

3,578

140

3.9

1993

3,640

95

2.6

1994

2,582

90

3.5

1990-1994

11,727

424

3.6

1995

1,920

57

3.0

1996

607

27

4.4

1997

1,625

32

2.0

1998

883

31

3.5

1999

4,065

86

2.1

1995-1999

9,100

233

2.6

2000

6,264

242

3.9

2001

2,618

104

4.0

2002

1,723

109

6.3

2003

1,423

69

4.8

2004

1,766

46

2.6

2000-2004

13,794

570

4.1

2005

706

37

5.2

2006

2,877

167

5.8

2007

2,923

82

2.8

2008

3,457

111

3.2

2009

1,248

58

4.6

2005-2009

11,211

455

4.1

Source: CWXSP—Coal Workers' X-ray Surveillance Program—Ref. No. 2011T02-12,

http://www2a.cdc.gov/drds/WorldReportData.

Some commenters, who stated that current risks of CWP were overstated in the proposed rule, suggested that recently observed cases were due to high coal ranks and/or excessive silica exposures associated with geographically limited areas within the United States. These commenters stated that the increase in prevalence of CWP is distinctly regional and that the proposed 1.0 mg/m

3

standard should not apply to regions that do not have an increase. Some of these commenters also said that CWP has been eliminated in the Midwest (i.e., Indiana, Illinois, and Western Kentucky) and pointed out that MSHA District 8 has a high participation rate in the CWXSP and the

lowest CWP rate in the country. A few commenters acknowledged that the prevalence of PMF has increased but, citing Wade et al. (2010), attributed the increase to greater silica exposure from drilling through rock. Some commenters also stated that MSHA should have examined its own silica exposure data before concluding that recently observed cases of CWP were caused by respirable coal mine dust exposures under the existing standard.

As noted in the proposed rule (75 FR 64462-64463), MSHA is aware that some cases of rapidly progressive CWP have been detected in a small percentage of miners diagnosed initially with CWP 1/0+; however, these cases are a small proportion of the larger group of miners across the U.S. who have been diagnosed with CWP 1/0+ that need to be studied to determine the reasons for the rapid progression (see Antao et al. 2005, 2006; Attfield and Petsonk, 2007).

The Wade et al. paper cited by commenters reported on a retrospective chart review of a group of 138 coal miners with PMF who were approved for benefits by the West Virginia State Occupational Pneumoconiosis Board between January 2000 and December 2009. The mean age of this group of miners was 52.6 years (40-77 years) and they had an average tenure of 30 years (7.5 to 47 years). Miners who worked as continuous mining machine operators or roof bolting machine operators had the highest occurrence of PMF (41% and 19%, respectively). The time of progression to PMF was studied in a subgroup of these miners when normal x-rays were available for comparison to x-rays showing advanced disease. In this subgroup of 43 miners, the time between the last normal chest x-ray and one showing advanced disease averaged 12.2 years (5 to 27 years). No data on quartz exposure or respirable coal mine dust was provided by Wade et al.

McCunney et al. (2009) noted in their review of epidemiology literature that coal dust has been described as “able to mask the fibrogenic activity of quartz” and that there are “distinct pathological differences between simple pneumoconiosis of CWP and silicosis.” Researchers initially thought that the active agent in respirable coal mine dust that was responsible for CWP development was quartz. However, research reported a poor correlation between radiological evidence of CWP and quartz concentration in the corresponding coal dust; there was no pattern between the quartz content of mixed dust and the probability of developing simple pneumoconiosis at quartz levels averaging 5 percent. Based on the collective weight-of-evidence of human epidemiology studies, animal investigations and

in vitro

evaluations contained in the preambles to the proposed rule (75 FR 64458, October 19, 2010) for this final rule and to the 2003 proposed rule on Verification of Underground Coal Mine Operators' Dust Control Plans and Compliance Sampling for Respirable Dust (68 FR 10837, March 6, 2003), it is apparent that quartz is not the predominant factor in the development of CWP. In fact, the results of large-scale epidemiological studies in Germany, the United Kingdom, France, and the United States indicate varying levels of risk of CWP, based on the type of coal regardless of silica content.

McCunney et al. (2009) also reported on the results of research conducted by Miller et al. (1995) in British coal miners. These miners participated in the Pneumoconiosis Field Research (PFR) program. As reported in the preamble to the proposed rule (75 FR 64462), that program, in addition to periodic chest x-rays, also collected separate industrial hygiene data that quantified typical concentrations of respirable dust and quartz for a variety of occupations within the mines. These exposure measurements were used to determine individual exposure profiles for participating miners. Miller et al. suggested that the rapid progression in radiological abnormalities, their relationship with quartz exposure estimates, and the strength of their relationship with lung function decrements resembled classical silicosis rather than CWP in a subpopulation exposed to quartz concentrations of about 10% at one specific mine. According to McCunney et al., however, recorded progressions of CWP to PMF in such cases may have resulted from misdiagnosing silicosis as CWP. McCunney et al. also reported similar findings of misdiagnosis in a case/control study of British coal miners that showed an effect of unusually high levels of quartz exposure on rapid CWP-progression.

The preamble to the proposed rule reported that NIOSH researchers determined that cases of rapidly progressive CWP are sentinel health events (75 FR 64468). Antao et al. (2005) identified a total of 886 cases of CWP among 29,521 miners examined from 1996 to 2002 in the CWXSP. CWP progression was evaluated in 783 of these miners; 277 (35.4%) were cases of rapidly progressive CWP, including 41 with PMF. The miners with rapidly progressive CWP were younger than miners without rapid progression, worked in smaller mines, and reported longer mean tenure in jobs involving work at the face (production area) of the mine. Many of these cases of rapidly progressive CWP developed in miners from eastern Kentucky and western Virginia. Eight cases showed progression of one subcategory over 5 years, 156 cases had progression equivalent to two or three subcategories over a 5-year period, and 72 cases had progression equivalent to more than three subcategories over a 5-year period.

Rounded opacities were the primary shape/size in 73% of the rapidly progressive cases compared to 50% in the non-rapidly progressive cases. Overall, the miners with rapidly progressive CWP were somewhat younger (mean age 48) than the remaining miners evaluated (mean age 51), but were similar in mean work tenure (27 to 28 years). Rapidly progressive cases were more likely to have worked in smaller mines than in larger mines. Rapidly progressive CWP cases reported longer mean tenure in jobs involving work at the face of the mine (19 years), compared to miners without rapid progression (17 years). These particular cases occurred in miners from eastern Kentucky and western Virginia (Antao et al., 2005).

Clusters of newly identified cases of advanced pneumoconiosis were surveyed in 2006 by ECWSHP teams that visited two counties in Virginia (Antao et al., 2006) and in eastern Kentucky and southwestern Virginia (Attfield and Petsonk, 2007). In March and May of 2006, a total of 328 underground coal miners employed in Lee and Wise counties in Virginia were examined. This was 31% of the estimated 1,055 underground miners in those counties. The mean age of examined miners was 47 years, and their mean tenure working in underground coal mines was 23 years. A total of 216 (66%) had worked at the coal face for more than 20 years; and 30 of the 328 miners (9%) had radiographic evidence of pneumoconiosis (i.e., category 1/0 or higher profusion of small opacities). Of these, 11 miners had advanced cases of CWP, including five with large opacities consistent with PMF and six with coalescence of small opacities on a background profusion of category 2. Among the 11 miners with advanced cases, the mean age was 51 years (range: 39-62 years), the mean tenure in underground coal mines was 31 years (range: 17-43 years), and the mean number of years working at the coal face was 29 years (range: 17-33 years). All 11 advanced cases met the radiographic criteria for rapidly progressive CWP. All reported at least one respiratory symptom (i.e., productive cough, wheeze, or shortness

of breath), the most common being shortness of breath (dyspnea). Four of the nine who underwent spirometry testing had abnormal results (Antao et al., 2006).

In a separate ECWSHP survey in 2006, pneumoconiosis rates were determined for 26 sites in seven counties in eastern Kentucky and southwestern Virginia (Attfield and Petsonk, 2007). A total of 975 (20%) of the 4,897 active underground miners in the counties participated; 37 (4%) of those tested had advanced pneumoconiosis. Medical records indicated that all 37 miners with advanced disease had worked underground for at least one interval of 10 years without a chest x-ray; 22 (59%) had worked for at least one interval of 20 years without a chest-ray, and 2 others had worked for more than 30 years without a chest x-ray. Attfield and Petsonk found that miners who worked at the coal face (not typically associated with silica dust exposure) and roof bolting machine operators (typically associated with higher silica dust exposure) with similar tenure underground (about 30 years) developed PMF at high rates. PMF was identified in 64% of the face workers and 42% of the roof bolting machine operators. Attfield and Petsonk examined disease development patterns in this population of miners since silicosis can develop faster than CWP. They found that 1 of 26 roof bolting machines operators (4%) progressed to PMF in less than 10 years, compared with 2 of 11 coal-face workers (18%).). Silica exposure was identified as only one of several factors possibly related to rapid disease progression in this population. The authors listed various potential explanations for the continued occurrence of advanced pneumoconiosis: The respirable dust standard may have been too high; failure to comply with or enforce respirable dust regulations; lack of adjusting disease prevention practices to accommodate changes in mining practices; and missed opportunities for miners to be screened for early disease. The 3 mm rounded opacities may or may not be associated with silica.

Suarthana et al. (2011) cited references by Laney et al. (2009) and Laney and Attfield (2010). These papers attempted to further illustrate what factors may be involved in the rapid progression of CWP to PMF by focusing on the presence of a specific type of x-ray findings frequently associated with silicosis (rounded pneumoconiotic opacities exceeding 3 millimeter (mm)—r-type) (Laney et al., 2009) and mine size (Laney and Attfield 2010) in U.S. coal miners who participated in the CWXSP. Laney examined NIOSH CWXSP data between 1980 to 2008 (2,868 radiographs showing ILO category 1 or greater small opacities out of a total of 90,973 available) found that r-type opacities, frequently associated with silica exposure, occurred in 201 radiographs representing 0.22% of the total number of radiographs examined. The 3 mm rounded opacities may or may not be associated with silica. It is a matter of sensitivity and specificity. It is not a silica-specific finding, but is often or frequently associated with silica exposure. Laney and Attfield examined NIOSH CWXSP data collected between 1970 and 2009 and evaluated the effect of mine size on the development of CWP and PMF. They found that miners working in small mines (fewer than 50 employees) had a significantly higher prevalence of CWP compared to miners who worked in large mines (with 50 or more employees). They reported that miners from small mines were five times more likely to have radiographic evidence of PMF (1% of miners) compared to miners from larger mines (0.2%). The Laney and Attfield (2010) study was the first to directly examine the relationship between miners' respiratory health and mine size in the U.S. They concluded that: there are distinct differences between large and small mines that potentially influence the amount and type of exposures; and the effect of small mine size on development of CWP risk was consistent across all mining states and was not confounded with coal rank or geographical region. They also found the small mine effect on CWP in other states, not just in thin seam mines that are primarily concentrated in Kentucky, Virginia, and West Virginia.

Other epidemiological studies on U.S. coal miners, discussed in the proposed rule (75 FR 64459), conclude that the rank of coal mined influences CWP rates among coal workers, suggesting that coal's carbon content is a factor in CWP risk (Huang et al., 2005, McCunney et al., 2009). According to these studies, coal from districts with lower rates of CWP (while considering similar levels of exposure to coal, both in concentration and duration) show that coal high in bioavailable iron (BAI) is associated with the highest risk of CWP. Results of

in vitro

studies with human and animal cell lines are consistent with the epidemiological data that suggest that risk of CWP is not based on quartz, but most likely due to the concentration of BAI.

In vitro

studies provide further support for the role of iron in the inflammatory process associated with CWP. (Huang et al., 2005; Zhang and Huang 2005; Zhang et al., 2002).

Huang evaluated the quality of coal, including BAI, as determined by the U.S. Geological Survey database of coal quality, across seven regions of the U.S. These data were compared to data from the first National Study of Coal Workers' Pneumoconiosis. The authors found that CWP prevalence was correlated with pyritic sulfur or total iron in the coals but not with coal rank or silica. They concluded that a significant correlation between CWP prevalence and levels of BAI exist, moderated by certain minerals in the coals that can interact and contribute to different levels of BAI and, therefore, different levels of CWP and associated COPD.

Although CWP and silicosis may have some similar clinical patterns, their etiology is different (McCunney et al., 2009; 75 FR 64458, October 19, 2010). Recent studies on U.S. coal miners illustrate this point (Antao et al., 2006; Attfield and Petsonk 2007; Laney et al., 2009, Laney and Attfield 2010, and Wade et al., 2011).

Miller et al. (1997, 2007) and Miller and MacCalman (2009) reported on the results of mortality research conducted in a group of British coal miners. These miners participated in the Pneumoconiosis Field Research (PFR) program. As reported in the preamble to the proposed rule (75 FR 64462), industrial hygiene data was collected as part of that program to quantify typical concentrations of respirable dust and respirable quartz for a variety of occupations within the mines. The data was used to determine individual exposure profiles for participating miners. The mortality of this large cohort of 17,820 coal miners was followed from 1970 through 2006 (Miller et al. 2007). The researchers presented alternative regression analyses to predict risk of mortality in relation to time-dependent estimates of individual exposures to respirable dust and respirable quartz. The researchers concluded that CWP mortality is directly related to exposure to respirable coal mine dust, which is a better single predictor of CWP risk than is respirable quartz exposure. These results are consistent with earlier findings (Hurley et al. (1982); Miller et al. (1997)) that respirable coal mine dust exposure is more closely associated with the development of pneumoconiosis than is quartz. Based on all of the available evidence, MSHA believes that respirable coal mine dust has a fibrogenic effect on the development of CWP in coal miners independent of the quartz or silica content of the coal. High silica content may accelerate the progression of CWP to PMF, the most severe form of CWP, but there is no evidence to suggest that

the presence of silica is a necessary condition for CWP, PMF, severe emphysema, or NMRD mortality.

Exposure to respirable coal mine dust from high rank coal is associated with greater risks of CWP and nonmalignant respiratory disease (NMRD) mortality. However, evidence of high risks in identified hot spots does not imply that risks in other areas are insignificant. Exposure to respirable coal mine dust from lower rank coal still places miners at significant excess risk for CWP and NMRD mortality. MSHA's Quantitative Risk Assessment (QRA) for the final rule shows that significant excess risks of CWP and NMRD mortality under the existing standard are present for miners at low rank coal mines—i.e., outside the geographic “hot spots” identified by some commenters. (See QRA, Tables 13, 14, 15, 17, and 18).

The CWXSP data from 2005-2009 published by Suarthana et al. show that some regions with lower rank coal, i.e., regions not identified as hot spots, also tend to have younger miners with less tenure. For example, in MSHA Districts 8, 9, and 10, tenure underground was less than 5 years for 49.1%, 47.0%, and 49.4% of the miners, respectively. Surveillance of underground coal miners in these regions indicates that CWP is occurring, though at lower rates, primarily due to the age and tenure profile of the miners. In the remaining Districts that mine bituminous coal, the median tenure was over 20 years (Table III-4).

Suarthana did not publish data from MSHA District 1, which mines anthracite, the highest ranked and most fibrogenic coal. District 1 surveillance data from NIOSH (USDHHS, CDC, NIOSH, Statistics for Underground Miners Working in MSHA District 01 (Anthracite Coal Mining Regions in Pennsylvania, 2011b) shows that during the period of 2004-2008, 67 anthracite miners participated in the ECWHSP. Age information was available for 58 miners. Mean age was 41 (range 18-69 years). Tenure information was available on 55 of these miners. The mean tenure was 17 years (range 0-45 years). Information on tenure at the face (production area) was available for 51 miners; mean years of face work was 17 years (range 1-45 years). The prevalence of CWP 1+ in 58 examined miners was 6 cases (or 10%). Commenters did not include anthracite coal mines in MSHA District 1 in their discussions of regional hot spots or suggest that silica was responsible for CWP at anthracite coal mines. Nevertheless, at exposure levels experienced over a 45-year occupational lifetime under the existing standard, anthracite coal mines present significant excess risks of CWP and NMRD mortality. (See QRA, Tables 13, 14, 15, 17, and 18). In the case of NMRD mortality, risks for anthracite coal miners are estimated to be far greater than for miners in the same occupations at high rank bituminous coal mines (QRA, Tables 17 and 18).

Overall, NIOSH surveillance data indicate that pneumoconiosis at the CWP 1/0+ level is occurring in underground coal miners across each MSHA Coal District in the United States; not just in the “hot spot” areas of southern West Virginia, eastern Kentucky, and western Virginia highlighted by some commenters.

Table III-4 shows that almost 50 percent of CWXSP participants in Districts 8, 9, and 10 have tenure of less than five years; and, yet, miners in those districts continue to develop CWP 1/0+ at 0.6% (16 cases), 1.2% (28 cases), and 2.3% (27 cases) respectively. As shown in Table III-1, miners continue to develop CWP in all MSHA Districts.

The commenters who questioned the validity of the reduction in the existing 2.0 mg/m

3

standard focused on the dose-response relationship and asserted that data generated from pre-1970 were out-of-date and should not be used for risk assessment purposes. MSHA's QRAs for the proposed and final rules assessed risk at current exposure levels. Data shown in Tables III-1 and III-2 indicate that CWP is continuing to develop, especially in miners with more underground tenure, as stated in MSHA's QRA. Almost all of these miners have worked only during the period while the existing 2.0 mg/m

3

standard has been in effect. While average exposures have been reduced, current exposure conditions place miners at significant risk of incurring material impairment of health or functional capacity over their working lives.

Other commenters suggested that MSHA selectively chose CWP data to include in the health effects assessment. They suggested that CWP prevalence is not increasing. In response, MSHA notes the data show that there was a reduction in prevalence of CWP in the 1990s until continued surveillance indicated that many cases of CWP were missed or newly developed (Attfield et al., 2009). Also, the prevalence of CWP increased with age and tenure. (See Tables III-1, III-2, III-3, and III-4.)

Table III-4—Coal Workers' X-Ray Surveillance Program (CWXSP)—Underground Coal Mining Survey Summaries of Observed Prevalence of CWP—2005-2009

1 2

Parameters

MSHA District

2

3

4

5

6

7

8

9

10

11

Median Dust

(in mg/m

3

)

0.79

(0.54-1.05)

0.96

(0.46-1.20)

0.80

(0.31-3.08)

0.55

(0.18-2.34)

0.75

(0.36-1.17)

0.69

(0.28-1.12)

1.14

(0.73-1.70)

0.98

(0.30-1.30)

1.14

(0.76-1.21)

0.99

(0.52-1.12)

Number of Miners

911

1,504

1,280

689

423

522

2,713

2,351

1,190

825

Age of Miners Examined:

≤19

1

10

0

0

0

6

43

73

28

3

20-29

84

148

106

29

29

67

682

686

339

64

30-39

129

207

216

79

70

103

613

529

346

91

40-49

142

218

282

242

174

192

564

524

222

175

50-59

471

785

607

316

132

143

729

464

240

424

≥60

84

136

69

23

18

11

82

75

15

68

Median Tenure (range)

25

(0-44)

22

(0-50)

25

(0-44)

27

(0-42)

24

(0-44)

20

(0-42)

5

(0-45)

5

(0-42)

5

(0-40)

24

(0-50)

Tenure %:

0-4 years

20.1

20.6

11.0

7.8

8.5

14.0

49.1

47.0

49.4

25.5

5-10 years

11.5

12.9

12.1

6.5

10.9

11.5

14.1

14.6

16.2

6.6

11-20 years

11.5

14.0

18.9

14.7

19.4

24.7

12.9

14.8

14.1

10.6

21-30 years

28.2

25.3

26.7

44.0

40.9

33.3

17.6

18.0

13.4

40.1

41-40 years

28.3

26.5

30.6

26.6

19.6

16.3

6.2

5.4

6.9

17.0

> 40 years

0.3

0.7

0.7

0.4

0.7

0.2

0.1

0.1

0.0

0.4

Observed Prevalence of X-ray Findings:

CWP 1/0+

22 (2.4%)

39 (2.6%)

125 (9.8%)

62 (9.0%)

58 (13.7%)

49 (9.4%)

16 (0.6%)

28 (1.2%)

27 (2.3%)

20 (2.4%)

Age of Cases:

≤19

0

0

0

0

0

0

0

20-29

1

1

0

0

0

0

2

1

2

0

30-39

0

0

1

1

0

1

2

5

2

0

40-49

3

8

23

25

28

19

1

8

10

4

50-59

14

23

89

30

29

28

10

13

12

10

≥60

4

7

12

6

1

1

1

1

1

6

1

Inspector-measured coal mine dust concentration data at mine level 1970-2008.

2

Observed prevalence is reported; Suarthana et al. estimated predicted CWP prevalence by using the 1992 Attfield and Morring (1992b) model. Attfield and Morring used mean job-specific dust levels used in the 1992 estimates, not mean mine specific dust levels. The paper reported median dust levels.

Source: Suarthana et al., 2011.

NIOSH reports prevalence in 5-year intervals for miners who voluntarily participate in the CWXSP. The numbers of miners who volunteer for medical surveillance vary over time (Table III-2) and the degree of detailed information provided also varies over time. Participation rates are dependent, in part, on availability of screening resources. NIOSH screens as many miners as possible through both the CWXSP (regular screening program) and the ECWHSP (enhanced screening program). Over time, the percentage of actively employed miners who volunteered for medical surveillance varied from 26% for the 1995-1999 time period to 34% for the 2000-2004 time period to 42% for the 2005-2009 time period, across all MSHA Districts (Table III-1). The requirements in final § 72.100 will increase participation rates. Final § 72.100 requires that each operator provide to each miner, including each surface coal miner, who begins work at a coal mine for the first time, an initial examination consisting of chest x-rays, spirometry, symptom assessment, and occupational history, and the opportunity to have the medical examinations at least every 5 years thereafter. MSHA expects that participation rates will increase due to the inclusion of surface miners in the screening/surveillance program. Other commenters suggested that more studies need to be completed before a revised standard can be developed since MSHA did not demonstrate that cases of CWP can be prevented under the proposed standard.

The QRA to the proposed rule demonstrated that cases of CWP, along with emphysema, silicosis, and chronic bronchitis, known collectively as “black lung,” could be prevented under the proposed respirable dust standards. The QRA relied on MSHA inspector and operator sampling data collected during the 5-year period 2004-2008 and predominantly relied on 4 epidemiologic studies from 1995, 2007, 2008, and 2009. These studies relied on coal mine dust samples and data collected from 1968 to 1988. The researchers, who conducted the studies that MSHA relied on for the proposed rule, took steps to mitigate biases in the data used to estimate the health effects of miners' exposure to respirable coal dust. The relationship between exposure to respirable coal mine dust and disease prevalence is essentially unchanged since the studies that MSHA relied on were conducted. In addition, MSHA upwardly adjusted operator samples and excluded abatement samples taken by MSHA to mitigate biases in the MSHA data. The QRA showed that exposures under the existing respirable coal mine dust standards are associated with cases of CWP, chronic obstructive pulmonary disease (COPD) including severe emphysema, and death due to non-malignant respiratory disease (NMRD). All of these outcomes constitute material impairments to a miner's health or functional capacity.

The QRA also analyzed and quantified the excess risk of miners incurring CWP or COPD, or dying due to NMRD, after 45 years of full-shift occupational exposure at levels currently observed in various exposure categories. Miners having different occupations and working at different locations face significantly different levels of respirable coal mine dust exposure. In every exposure category, including clusters of occupational environments showing the lowest average dust concentrations, current exposure conditions place miners at significant risk of incurring each of the material impairments considered.

Finally, the QRA projected the risk of material impairments after the proposed respirable dust standards were applied to each shift. Several provisions in this final rule will singularly lower coal miners' exposure to respirable dust and reduce their risks of disease and disease progression. These provisions include lowering the respirable dust standard, full-shift sampling to account for occupational exposures greater than 8 hours per shift, changing the definition of normal production shift, use of CPDMs for sampling, basing noncompliance determinations on MSHA inspectors' single shift sampling, revising the sampling program, requiring operator corrective action on a single full-shift operator sample, and changing the averaging method to determine compliance on operator samples. MSHA's QRA estimates the reduction in health risks when two provisions of the final rule are implemented—the final respirable dust standard and single shift sampling. The QRA shows that these two final provisions would reduce the risks of CWP, severe emphysema, and death from non-malignant respiratory disease (NMRD). For instance, the QRA for the final rule projects, over a 45-year occupational lifetime, significant improvements in almost every underground job category and at least 6 surface categories. Large aggregated improvements are also projected for longwall tailgate operators and continuous mining machine operators.

While the final 1.5 mg/m

3

standard will reduce the risk of impairment, disease, and premature death, estimates from MSHA's revised QRA reveals remaining risk at the final standard. However, MSHA believes that other provisions of the final rule will diminish these risks. The impacts of these other final provisions were not considered in the QRA. Cumulatively, MSHA expects that the final provisions will reduce the continued risks that miners face from exposure to respirable coal mine dust and would further protect them from the debilitating effects of occupational respiratory disease.

It has been over 40 years since the 1969 Coal Act was enacted. Exposures to respirable coal mine dust have been reduced with resultant reduction in disease prevalence. Table III-2 shows that: In the time period from 2005 to 2009 miners with over 25 years of tenure in underground coal mining have a CWP 1/0+ prevalence of 6.9%; and miners with only 0-9 years of tenure have CWP 1/0+ prevalence of 0.6% for that same time period. These miners are younger and have less cumulative exposure to respirable coal mine dust. The average prevalence of CWP 1/0+ for the period 2005 to 2009 was 4.1%.

The overall prevalence of CWP 1/0+ in all miners was 2.7% (See Table III-1) for the 2005-2009 time period. However, NIOSH data show that CWP 1/0+ is still occurring at significant levels in the active mining population. With continued surveillance over time, the number of CWP 1/0+ cases detected annually fluctuates; however, significant risk of material impairment of coal miners' health still remains, as noted in the QRA for this final rule.

Smoking in miners was mentioned by some commenters as a causative factor for observed lung disease in miners.

Exposure to coal mine dust is an independent factor in the development of CWP. Smoking is a risk factor for the development of lung disease, including cancer, COPD, and emphysema. Smoking and exposure to respirable dust have an additive effect on the development of COPD in miners. However, as shown in the Health Effects section of the preamble to the proposed rule, significant levels of NMRD, such as COPD and emphysema, occur in nonsmoking miners caused by their exposure to respirable coal mine dust.

In the first round of the CWHSP, 54.4% of underground coal miners were smokers, 25.5% were former smokers, and 20.1% were never smokers (Beeckman, et al., 2001; Beeckman, et al., 2002). Estimates of the current prevalence of smoking in coal miners (by MSHA District) are shown in Table III-5. This data set was reported as part

of the ECWHSP data on NIOSH's Web site. Smoking status among surveyed coal miners is currently estimated to be 22% smokers, 27% former smokers, and 51% never smoked. Again, since respirable coal dust exposure and smoking have an additive effect on the occurrence of COPD in smoking miners, MSHA believes the reduction in respirable dust levels in mining due to implementation of the final rule, coupled with the reduction in smoking in the mining population, also would have a beneficial effect on reducing the occurrence of NMRD in this population over time. (See Section IV, Health Effects, in the preamble to the proposed rule (75 FR 64458), Green et al., 1998a, and Kuempel et al., 2009b.)

Table III-5—Smoking Prevalence Among Coal Miners Participating in the ECWHSP, 2006-2010

MSHA district

Number of miners

Smoking status

Never (%)

Former (%)

Current (%)

1

58

22 (38)

8 (14)

28 (48)

2

664

356 (54)

200 (30)

108 (18)

3

1,019

531 (52)

264 (26)

224 (22)

4

1,059

573 (54)

250 (24)

236 (22)

5

629

314 (50)

170 (27)

145 (23)

6

374

182 (49)

79 (21)

113 (30)

7

443

205 (46)

109 (25)

128 (29)

8

667

312 (47)

205 (31)

150 (22)

9

879

462 (53)

262 (30)

155 (18)

10

135

78 (58)

39 (29)

18 (13)

11

565

299 (53)

158 (28)

108 (19)

Total

6,492

3,334 (51)

1,744 (27)

1,413 (22)

Source: USDHHS, CDC, NIOSH, CWHSP, Statistics for Underground Miners, Districts 1 to 11, 02/13/2011.

MSHA's existing standard permits overexposures above the respirable coal mine dust standard due to averaging samples. Some commenters expressed concern that the proposed single sample provision would increase the number of citations that a mine operator receives, but would not affect a miner's long-term exposure and the subsequent development of chronic health effects.

The single sample provision in this final rule is changed from the proposal and only applies to MSHA inspector samples. MSHA does not anticipate that this final provision will, over the long term, increase the number of operator citations. A single sample that exceeds the standard would not cause or significantly contribute to disease. However, cumulative overexposures—masked when used as part of an average based on multiple samples—could cause or significantly contribute to development or progression of diseases, with each overexposure being an important factor contributing to disease. Compared to the current method of dust sampling, single full-shift samples will reduce a miner's cumulative exposure to respirable coal mine dust and the risk of developing occupational respiratory disease. For these reasons, single full-shift samples above the standard must be controlled so that miners' cumulative exposure is not increased beyond the level that will induce disease.

Final § 72.800 provides that the Secretary will use a single, full-shift measurement of respirable coal mine dust to determine the average concentration on a shift since that measurement accurately represents atmospheric conditions to which a miner is exposed during such shift. Additional discussion on single full-shift sampling is located elsewhere in this preamble under § 72.800.

Some commenters questioned the relationship between respirable coal mine dust exposure and development of NMRD, such as COPD and chronic bronchitis. Epidemiological studies that were discussed in the Health Effects section of the preamble to the proposed rule (75 FR 64460) found that coal miners from the United States, Great Britain, Australia, France, Asia, and South Africa developed decreased lung function that was proportional to the miners' cumulative respirable coal mine dust exposure. Exposure to higher respirable coal mine dust levels over a working lifetime resulted in more miners experiencing a significant loss of lung function. These studies illustrate a strong dose-dependent relationship between respirable coal mine dust exposure and subsequent development of obstructive lung diseases, such as lung function impairment, chronic bronchitis, and emphysema (75 FR 64465). The decline in lung function is not linear; studies indicate that there may be some recovery following a year or two of exposure. But, the recovery can be temporary and is affected by continued exposure. As the number of years working in mining grows, the adverse effect on lung function does as well.

Chronic exposure to respirable coal mine dust causes chronic bronchitis, as was found in 35% of a mining population in the United States. This disease is different from that caused by tobacco smoke. Coal mine dust-related bronchitis is associated with deposits of fibrous tissue, mineral pigment, and inflammatory cells in the walls of membranous and respiratory bronchioles and alveolar ducts. This condition is referred to as mineral dust airways disease. Emphysema is caused both by smoking and coal mine dust exposure. Severity of disease has been related to dust content of the lungs and cumulative lifetime coal mine dust exposure. Kuempel et al. (1997b) showed that significant decrements in lung function occur by the age of 65 years in long-term nonsmoking miners exposed to an average respirable coal mine dust concentration of 0.5 mg/m

3

.

One commenter stated that for proper evaluation of the health effects studies, more information is needed; such as miner jobs, number of job changes, time spent on specific jobs, number and size of mines, and employment in different mines.

Many of the studies reported in the proposed rule had this type of detail in the data collected from certain mining populations, although only summary data were reported in the published papers. This type of detail was available in the industrial hygiene (IH) surveys conducted by British researchers as part of the Pneumoconiosis Field Research (PFR) program established in the early

1950s and explained in the proposed rule (75 FR 64462). Concurrent with the health surveys, a separate IH assessment was conducted as part of the PFR program that quantified typical concentrations of respirable dust and quartz for a variety of occupations within the mines. These exposure measurements were linked to data from payroll systems on the times worked by each miner in the same occupations. This IH assessment produced individual and period-specific estimates of exposure to respirable dust and quartz (MacCalman and Miller, 2009; Attfield and Kuempel, 2003; Scarisbrick and Quinlan, 2002).

In addition, the U.S. National Coal Study (NCS) is a long-term epidemiologic study, limited to miners in a selected group of mines with various seam heights, mining methods, coal types, and geographic locations. Many of the published peer-reviewed epidemiological studies reported in the proposed rule's health effects section are based on data from the NCS. In those studies, estimates of cumulative dust exposures were given. Examples of these studies include Henneberger and Attfield (1997) and Kuempel et al. (1997b). These papers were reviewed in the development of the proposed rule (75 FR 64460).

Similarly, some commenters identified seam height or mine size as potential factors that were not modeled in the regression analyses but could potentially contribute to the observed frequency of adverse health effects. To date, there are some epidemiological studies that have directly explored the association of coal seam height or mine size and CWP, PMF, non-malignant respiratory diseases, emphysema, or FEV

1

declines. However, no epidemiological coal miner studies have modeled respirable coal mine dust and non-malignant respiratory diseases while examining the confounding effect of coal seam height. The available studies are described below.

Peters et al. (2001) studied the influence of coal seam height on lost-time injury and fatality rates at small underground bituminous coal mines. Nonetheless, Peters did not examine the association of coal seam height and NMRDs or FEV

1

declines among coal miners.

Suarthana et al. (2011) stated that low seam height likely contributed to excess CWP cases. It was also noted that thin seam mining poses difficulties because the rock surrounding the coal seam often has to be cut to permit equipment to be employed effectively (also see Pollock et al., 2010). Suarthana et al. (2011) noted that the average coal seam height was lower in central Appalachia than in other regions (median seam height 60 (range 26-138) inches versus 79 (range 31-168 inches; p<0.001). Data on seam height were obtained from the MSHA Standardized Information System (MSIS) for the time period of 2005-2009. Suarthana concluded that the observed prevalence of CWP substantially exceeded predicted levels in central Appalachia. Therefore, coal seam height was reported as a likely factor contributing to the observed elevated CWP rates. However, Suarthana stated that further study is needed to characterize the factors responsible for elevated CWP rates. Overall, no direct association between CWP and coal seam height was observed.

Cowie et al. (2006) found FEV

1

deficits in 1,267 (18%) British coal miners. Cumulative respirable dust exposure ranged up to 726 gh/m

3

(gram hours per cubic meter) with a mean of 136 gh/m

3

; on average an exposure to cumulative respirable dust of 100 gh/m

3

was associated with a reduction in FEV

1

of 0.0631. In addition, an increase of 50 gh/m

3

was associated with an increase of about 2% in the proportion of men with small deficits in FEV

1

(−0.367 deficit); 1.5% to 2% for medium deficits (−0.627) depending on age; and a similar pattern was observed for large deficits (−0.993), but with smaller increases. Cowie stated that these results may be due to differences in seam height, mechanical breathing efficiencies, or the workload associated with limb size or body mass. Yet, the association of FEV

1

deficits among coal workers and seam height was not explored.

In terms of FEV

1

declines, Wang et al. (1999) investigated the association between occupational exposure to dust and clinically important FEV

1

declines in a group of 310 underground coal miners (cases) and their matched mining referents with stable lung function. This study defined a seam height <50 inches as a low seam mine, and compared the total years worked in low seam mines between two groups 1) cases (310 underground coal miners) and 2) matched partners (referents); cases and referents averaged 7.2 and 5.4 total years worked (p=0.21), respectively. However, the authors did not investigate the association between clinically important FEV

1

declines and mine seam height and mine size. Overall, logistic regression models conducted in this analysis did not explore the relationship between clinically important declines in FEV

1

and seam height.

Laney et al. (2010) acknowledged that their study is the first to directly examine miner respiratory health and mine size. Laney also highlighted that the prevalence of CWP and PMF increased between the 1900s and the 2000s for mines of all sizes. The prevalence of CWP is 6.5% in the 1970s, 2.5% in the 1980s, 2.1% in the 1990s and 3.2% in the 2000s. The prevalence of PMF was higher in larger mines (50+ miners) in the 1970s and 1980s; whereas, the prevalence was higher in smaller mines (<50 miners) in the 1990s and 2000s.

Laney and Attfield (2010) examined NIOSH CWXSP data collected between 1970 and 2009 and evaluated the effect of mine size on the development of CWP and PMF. They found that miners working in small mines (fewer than 50 employees) had a significantly higher prevalence of CWP compared to miners who worked in large mines (with 50 or more employees). They reported that miners from small mines were five times more likely to have radiographic evidence of PMF (1% of miners) compared to miners from larger mines (0.2%).

Suarthana et al. (2011) found that mine size (e.g., number of employees in a mine) may be associated with higher CWP prevalence levels. The researchers used the Attfield and Morring (1992b) exposure response model versus the original Attfield and Morring (1992a) model that used mean job-specific dust levels. The researchers stated that they did not have the dust level information specific to all jobs; instead, the researchers estimated dust exposure using the mean mine-specific dust level based on MSHA compliance data. The median measured dust concentration and range are reported at the mine level. However, the QRA for the proposed rule estimated CWP risk based on mean job-specific dust levels. The authors excluded underground coal miners from MSHA district 1 due to the small number of participants (n=55) and difference in coal type (anthracite) compared to the other districts in the analysis (bituminous). In addition, the authors state that further study is needed to characterize the factors responsible for elevated CWP rates; the results point to a need for greater vigilance in controlling coal mine dust, especially that which arises from rock cutting.

One commenter said that MSHA failed to consider in the proposed rule other factors that NIOSH discussed in its 2011 Current Intelligence Bulletin 64, such as free radicals, particle occlusion, and bioavailable iron.

MSHA did not use the 2011 NIOSH literature update in the development of the proposed rule because it was not final when the rule was published on October 19, 2010. However, the Health Effects section in the preamble to the proposed rule included a section called Hazard Identification (75 FR 64458) that discussed these factors and how they affect the toxicity of coal particles.

One commenter stated that MSHA analyzed only part of the NIOSH data. This commenter, however, did not provide detail about what data were missing.

The preamble to the proposed rule stated that it summarized the health effects from occupational exposure to respirable coal mine dust. This summary included a literature review on this same subject published in its proposed rule on Plan Verification, which was published on March 6, 2003 (68 FR 10784). The literature referenced in that document pre-dated 1999. The October 19, 2010, proposed rule updated the health effects information that was published in 2003 and discussed the more recent literature dating from 1997 to mid-2009 (75 FR 64458). MSHA reviewed extensive literature not only published by NIOSH but also published by researchers in other countries, such as France, Britain, Taiwan, Netherlands, Germany, China, and South Africa.

One commenter stated that during the 2009 spot inspections, MSHA personnel routinely observed improper sampling procedures for dust collection, improper handling of sampling devices, and improper maintenance and calibration of approved sampling devices. This commenter stated that improper procedures must be corrected before lowering the respirable dust standards.

In response, MSHA points out that the QRA to the proposed rule was based on both MSHA inspector samples and operator samples during 2008 and 2009. MSHA's enforcement experience is that most mine operators attempt to be in compliance with the existing respirable dust standards during MSHA inspector sampling. However, even if proper sampling procedures, proper handling of sampling devices, and proper maintenance and calibration of approved sampling devices had been used, this Health Effects section and the QRA to the proposed rule establish that at the existing standard of 2.0 mg/m

3

, cases of CWP and COPD continue to occur.

A commenter stated that MSHA does not really know how much dust that miners are exposed to and therefore needs to conduct a study using the CPDM to determine the exposure before reducing the exposure level.

Dose-response relationships have been determined by using the approved sampling device (gravimetric or CMDPSU) over the last 35 years. NIOSH and MSHA will continue to study the effects of respirable coal mine dust; however, the relationship between exposure and effect is well established. The final rule will lower miner exposure to respirable coal mine dust thus resulting in less respiratory disease in the miner population.

B. Quantitative Risk Assessment (QRA)

Below is a summary of the quantitative risk assessment (QRA) in support of the final rule. The QRA for the final rule revises the QRA in support of the proposed rule. The QRA for the proposed rule (US Department of Labor, Quantitative Risk Assessment in Support of Proposed Respirable Coal Mine Dust Rule, September 2010) addressed the proposed respirable coal mine dust standard of 1.0 mg/m

3

, and 0.5 mg/m

3

for intake air and for part 90 miners. The QRA for the final rule addresses the final 1.5 mg/m

3

respirable coal mine dust standard as well as the 0.5 mg/m

3

standard for intake air and part 90 miners. In response to public comments, it also includes an uncertainty analysis.

The QRA for the proposed rule was peer reviewed by independent scientific experts at NIOSH and OSHA. The full text of that QRA and the peer reviewers' reports can be accessed electronically at

http://www.msha.gov/regs/QRA/CoalDust2010.pdf

and

www.regulations.gov

. MSHA posted all comments on the QRA for the proposed rule at

http://www.msha.gov/REGS/Comments/2010-25249/CoalMineDust.asp

and on

www.regulations.gov

. The full text of the QRA for the final rule can be accessed electronically at

http://www.msha.gov/regsqra.asp

and

www.regulations.gov

.

The QRA for the final rule, like the QRA for the proposal, addresses three questions: “(1) whether potential health effects associated with current exposure conditions constitute material impairments to a miner's health or functional capacity; (2) whether current exposure conditions place miners at a significant risk of incurring any of these material impairments; and (3) whether the final rule will substantially reduce those risks.”

After summarizing respirable coal mine dust measurements for miners in various occupational categories, Part 1 of the QRA for the final rule shows that exposures at existing levels are associated with CWP, COPD including severe emphysema, and death due to NMRD. All of these outcomes constitute material impairments to a miner's health or functional capacity.

Part 2 of the QRA for the final rule analyzes and quantifies the excess risk of miners incurring CWP or COPD, or dying due to NMRD, after 45 years of full-shift occupational exposure at levels currently observed in various exposure categories. Miners having different occupations and working at different locations face significantly different levels of respirable coal mine dust exposure. In every exposure category, including clusters of occupational environments showing the lowest average dust concentrations, current exposure conditions place miners at a significant risk of incurring each of the material impairments considered.

Part 3 of the QRA for the final rule projects the risk of material impairments after the final respirable coal mine dust standards are applied to each shift. It estimates the reduction in health risks when two provisions of the final rule are implemented—the final respirable dust standard and single shift sampling. The QRA shows that these two provisions would reduce the risks of CWP, severe emphysema, and death from NMRD. Additionally, MSHA believes that other provisions of the final rule (e.g., full-shift sampling, changing the definition of normal production shift, use of CPDMs for sampling, revising the sampling program, and requiring operator corrective action based on a single full-shift operator sample will further diminish these risks.

The final rule is projected to have a greater impact on reducing risk for underground miners than for surface miners. Although the final rule will benefit coal mine workers who are exposed to average respirable dust concentrations both above and below the final 1.5 mg/m

3

and 0.5 mg/m

3

standards, it is projected to have its greatest impact on workers who currently experience frequent exposures to dust concentrations above the final standards. Underground work locations exceed the final respirable dust standards on many more shifts than surface locations and also tend to experience higher average dust concentrations.

The final rule is expected to reduce the risks of CWP, severe emphysema, and NMRD mortality attributable to respirable coal mine dust exposures. Table 28 of the QRA for the final rule contains the projected reduction in these risks for each occupational category. For progressive massive

fibrosis (PMF), the most severe stage of CWP considered, reductions of up to 56 excess cases per thousand are projected for underground workers at age 73, depending on occupation. For severe emphysema at age 73, the projected improvements for underground workers range up to a reduction of 34 cases per thousand depending on occupation. Again for underground workers, the reduction in excess cases of death due to NMRD by age 85 is projected to range up to 6 per thousand, depending on occupation. For surface workers, reductions exceeding 1 case per thousand exposed miners are projected for PMF and severe emphysema in several occupational categories. Excess risks per thousand part 90 miners are projected to decline by 19 cases of PMF at age 73, 14 or 22 cases of severe emphysema at age 73 (depending on race), and 4 cases of NMRD mortality by age 85.

Part 4 of the QRA for the final rule contains an analysis of uncertainties in the projected reductions in risk. This includes both a quantitative analysis of sensitivity to the assumptions and methods used and a qualitative discussion of the maximum range of credible estimates for projected reductions in respirable coal mine dust exposures. MSHA's best estimates were found to lie near the middle of the range produced by alternative assumptions.

In all of its calculations, the QRA assumes that miners are occupationally exposed to respirable coal mine dust for a total of 86,400 hours over a 45-year occupational lifetime (e.g., either 48 weeks per year at 40 hours per week, 32 weeks per year at 60 hours per week, or any other work pattern that amounts to an average of 1,920 exposure hours per year). Current health risks are greater than those shown in the QRA for miners working more than 1,920 hours per year.

In addition, the final rule also tightens the requirement for normal coal production necessary for a valid dust sample, requires the use of CPDMs, revises the dust sampling program, and requires operator corrective action on a single, full-shift operator sample. These provisions are expected to further reduce respirable dust exposures, thereby resulting in improvements greater than those shown in the QRA. For a discussion of the benefits of the final rule, see Chapter V of the REA.

Public comments on the QRA for the proposed rule addressed five issues: (1) Hazard identification, (2) exposure-response models and possible threshold effects, (3) reliance on mean and cumulative exposures, (4) method of projecting exposures and risk reductions under successful implementation of final rule, and (5) uncertainty in the QRA's results.

1. Hazard Identification

Some commenters stated that the QRA for the proposed rule did not contain a hazard identification section, consisting of toxicological, epidemiological, or clinical evidence addressing whether the existing standard of 2.0 mg/m

3

causes incremental harm to miners' health.

MSHA provided a comprehensive evaluation of the critical scientific evidence supporting a causal connection between respirable coal mine dust exposures at the current level and adverse health effects in Section IV, Health Effects, of the preamble to the proposed rule, and in Section 1(d) of the QRA for the proposal which pertained to health effects and material impairment under current exposure conditions.

MSHA agrees with the commenters that the hazard identification step should reflect current biological understanding of the inflammatory mode of action for lung diseases induced by inhalation of coal mine dust. Section IV.B.4 of the preamble to the proposed rule discussed a variety of biological mechanisms including inflammation.

A few commenters stated that the QRA relied on spurious associations among historical trends to establish a causal relationship between respirable coal mine dust exposures and adverse health effects. Associations among historical trends played no role in the QRAs for the proposed or final rules. None of the three published regression analyses on which the QRAs rely regress one time trend against another. Instead, they quantify the relationship between varying levels of accumulated respirable coal mine dust exposure and the relative frequency of CWP (CWP1+, CWP2+, and PMF), severe emphysema, and premature death due to NMRD.

5

The subjects, i.e., data points, of these regression analyses are not rates of disease corresponding to aggregated exposure levels in particular years. Rather, the data points of the regression models are individual miners who were more or less simultaneously exposed to different levels of respirable coal mine dust. Thus, those miners who were exposed to low cumulative exposures serve as an internal control group compared to miners who were exposed to higher cumulative exposures.

5

See Appendices I, J, and K of the QRAs for the proposed and final rules.

Since the pertinent studies included miners whose lifetime cumulative exposures fell well below the existing standards, these studies provide MSHA with a basis for determining whether exposure levels under the existing respirable coal dust standards cause incremental harm to miners' health. This topic was addressed in sections 1(d) and 2 of the QRA for the proposal. The conclusion, subject to assumptions described in Section 2(f) of the QRA, is that current exposure conditions which, as shown in Tables 6 and 12 of the QRA for the proposal, are generally below the existing 2.0 mg/m

3

and 1.0 mg/m

3

standards, place miners at a significant risk of incurring each of the material impairments considered. MSHA reaches the same conclusion in the QRA to the final rule.

A few commenters stated that MSHA improperly relied on estimates of current disease prevalence from the NCWHSP, which was initiated in 1970 and is administered by NIOSH. These commenters stated that the NCWHSP surveillance data is biased due to issues related to the accuracy and precision in the diagnosis of CWP and PMF, low miner participation rates, limited exposure data, and other design and analysis limitations, e.g., participant self-selection.

MSHA did not rely on the NCWHSP surveillance data in its QRAs for either the proposed or final rules. The relatively low participation rates, potential self-selection biases, and a lack of correspondent exposure histories for the individual miners involved limit the use of the surveillance data as support for the QRAs. The QRAs primarily relied on three epidemiologic studies: Attfield and Seixas (1995); Kuempel et al. (2009a); and Attfield and Kuempel (2008). These three studies are consistent with the commenters' statement that estimates of current disease prevalence should characterize historical exposures of individual miners and incorporate cumulative exposure metrics in the analyses to check for a pattern of increasing disease risk with increased dust exposure level.

However, NCWHSP surveillance data are useful in establishing that significant health hazards persist under existing respirable coal dust exposure conditions. Although the utility of these data for quantitative risk assessment is limited, they do show there is an unacceptably high incidence of respirable coal mine dust-related disease among miners whose exposure came entirely after adoption of the existing respirable coal dust standards. (See Section III.A., Health Effects, in this preamble.)

Sections 1(d) and 2 of the QRAs for the proposed and final rules use the

National Study of Coal Workers' Pneumoconiosis (otherwise known as NCS) data to address the question of whether a lifetime of occupational respirable coal mine dust exposure at the existing standard presents a significantly increased risk of adverse health effects (also see Goodwin and Attfield (1998) and Brower and Attfield (1998)). Unlike the surveillance data, the NCS data contain information on both the health and the respirable coal mine dust exposure of individual miners.

Dust exposure estimates are calculated by summing the products of time worked in each job within an individual miner's work history with dust concentration data from the exposure matrix derived by Seixas et al. (1991). Brower and Attfield (1998) found that the self-reported occupational history information on standardized questionnaires in the NCS collected from U.S. underground coal miners is reliable and that the amount of bias introduced by recalling past employment history is minimal. The NCS is further described in Section III.A of this preamble.

Some commenters discussed possible radiological misclassification in the NCS data.

6

However, these commenters did not dispute the appropriateness of using this type of study to establish a dose-response relationship that can be used effectively in a quantitative risk assessment.

6

Uncertainty due to radiological misclassification is addressed separately in Section 2, Exposure-Response Models and Possible Threshold Effects, (b) Bias due to Errors in Diagnosis and (c) Bias due to Errors in Exposure Estimates. See Wagner et al., 1992.

Some commenters challenged the QRA's findings of significant health risks from exposure at the existing 2.0 mg/m

3

standard over an occupational lifetime. MSHA addresses issues raised by these commenters in the following subsections: (a) CWP, including PMF; (b) severe emphysema; and (c) mortality due to NMRD.

a. CWP, including PMF

Some commenters acknowledged that the exposure-response analyses of respirable coal mine dust and CWP2+ show strong associations for high rank coal, with increased prevalence below the existing standard. However, these commenters maintained that there are no apparent increases in CWP2+ for low rank coals at exposures below the existing 2.0 mg/m

3

standard. According to the commenters, the prevalence of CWP2+ and PMF predicted by the exposure-response models for miners experiencing an occupational lifetime of exposure to respirable coal dust at 2.0 mg/m

3

from low or medium rank coal is less than the “background” rate, or prevalence, of positive radiographic findings among workers with no occupational exposure to respirable coal mine dust.

The commenters assumed, in reaching their conclusion, that the background prevalence, which had been shown to be approximately five percent for CWP1+ among 60-year-old non-exposed workers, was also five percent for CWP2+ and PMF. MSHA stated during one of the public hearings on the proposed rule that it is not appropriate to compare predictions of CWP2+ prevalence to the background prevalence for CWP1+.

The 1995 Attfield/Seixas study provides a formula, shown in Appendix I of the QRAs for the proposed and final rules, that enables estimation of the background prevalences for CWP1+, CWP2+, and PMF. Based on this formula, Table III-6 below shows the estimated background prevalences specific to CWP1+, CWP2+, and PMF, along with the corresponding prevalences predicted for miners exposed to respirable coal mine dust concentrations averaging 2.0 mg/m

3

for an occupational lifetime of 45 years. The predicted prevalences of CWP1+, CWP2+, and PMF for miners exposed to respirable coal mine dust from low/medium rank coal are all far greater than the corresponding background prevalence. For miners exposed to high rank coal, the difference is even greater.

All of the estimated excess risks shown in both QRAs for exposed miners are denoted as “excess” risks precisely because the background prevalence has been subtracted from the predicted prevalence among exposed miners. Therefore, the calculation of excess risk always yields zero when exposure equals zero (i.e., no known occupational exposure); and, for exposed miners, excess risk is the increase in predicted prevalence from background. For example, at age 73, the center graph in Figure 10 of the QRAs for the proposed and final rules shows an excess risk of 156 cases of CWP2+ per thousand miners exposed for 45 years to respirable coal mine dust from low/medium rank coal at an average concentration of 2.0 mg/m

3

. The same result is obtained from Table III-6 below by subtracting the background prevalence of 6.2 percent (62 cases per thousand) from the prevalence of 21.8 percent (218 cases per thousand) shown for exposed miners (i.e., 21.8%-6.2%=15.6%: 156 cases per thousand miners, compare with Figure 10 in both QRAs).

Table III-6—Expected Prevalence (Percentage) of Radiographic Findings Indicating CWP and PMF, Based on Attfield/Seixas Logistic regression model

Age

Background

(zero exposure)

CWP 1+

CWP 2+

PMF

45-year exposure at 2.0 mg/m

3

top entry is for low/medium rank coal

bottom entry is for high rank coal

CWP 1+

CWP 2+

PMF

60

5.3

1.1

0.7

17.8

4.7

2.2

32.7

14.7

9.3

65

7.6

2.2

1.3

24.1

8.7

4.2

41.7

25.2

16.9

73

13.3

6.2

3.9

37.1

21.8

11.6

57.0

49.6

37.8

Moreover, systematic error or bias due to systematic misinterpretation of radiographic data would be equally present in the results for both exposed and unexposed miners. Therefore, the effect, if it exists, of such misinterpretations should be canceled when background prevalence is subtracted from predicted prevalence to form the estimates of excess risk provided in the QRAs for the proposed and final rules. Some commenters

emphasized potential biases of this type but failed to mention that comparing the frequency of positive radiographic findings for exposed miners with the appropriate background rates serves to control for such biases.

b. Severe Emphysema

Some commenters stated that the weight of the epidemiological evidence fails to support any clinically significant deficits in forced expiratory volume (FEV

1

) or any increased occurrence of chronic obstructive pulmonary disease (COPD) at cumulative respirable coal mine dust exposures equivalent to an occupational lifetime at the existing standard. [See the proposed rule discussion on emphysema; Green et al., 1998a; Kuempel et al., 2009a and 1997b]. However, the only metric used to support this assertion was the average loss in FEV

1

attributable to respirable coal mine dust exposure, across the entire population of exposed miners. Section 1(d)(ii) of the QRAs for the proposed and final rules points out that averaging FEV

1

loss across a population can mask the effects of exposure on susceptible sub-populations. Averaging fails to reveal the risk of FEV

1

reductions that exceed the average by a clinically significant amount.

7

Dust exposure at a given level may affect susceptible individuals to a far greater extent than what is suggested by the average effect. This type of masking is avoided when, as in NIOSH's 1995 Criteria Document, findings are expressed in terms of the prevalence of clinically significant outcomes.

7

The term “clinical significance” is defined as a difference in effect size considered by experts to be important in clinical or policy decisions, regardless of the level of statistical significance (Last, John M., ed. 2001.

A Dictionary of Epidemiology,

Fourth Edition. New York: Oxford University Press, Inc.

For example, the average reduction in FEV

1

predicted by the Soutar/Hurley (1986) estimate is less than 140 ml after 45 years of occupational exposure to respirable coal mine dust at 2.0 mg/m

3

. However, this average reveals little or nothing about the effects on individual miners. If the exposure effects were clinically significant in as little as one percent of all cases (10 cases per thousand), then this would constitute a significant increase in risk associated with exposure. An average reduction in FEV

1

of 140 ml or less does not preclude the possibility that the reduction exceeds 300 ml or even 1,000 ml in a substantial portion of the exposed population. Instead of solely focusing on the average loss in pulmonary function associated with respirable coal mine dust exposure, MSHA also considers the rate at which clinically significant lung function deficits have occurred. Table III-7 (reproduced from Table 7-3 of the NIOSH Criteria Document) provides estimates of the excess risk, i.e., the number of miners expected to develop a clinically significant deficit in FEV

1

per thousand exposed miners after an occupational lifetime of exposure to various concentrations of respirable coal mine dust.

8

Although the commenters correctly counted the Attfield and Hodous (1992) study that showed no clinically significant average reduction in FEV

1

, Table III-7 shows that the average reduction is not the only outcome of interest. As shown in Table III-7, the Attfield and Hodous (1992) study also shows clinically significant reductions in FEV

1

in a substantial number of cases per thousand exposed miners. Specifically, for miners at age 65 occupationally exposed to a mean respirable coal mine dust concentration of 2.0 mg/m

3

over a 45-year working lifetime, the estimated excess risk of FEV

1

< 65% of the predicted normal value is 9 per 1,000 for never smokers in the western region and 12 per 1,000 for the eastern region.

9

8

The values shown in Table III-7 represent excess risks because they are adjusted to discount background rates of clinically significant deficits in FEV

1

for unexposed workers at age 65.

9

Table III-7 is based on two studies: Attfield and Hodous (1992) and Seixas et al. (1993). The commenters indicated that the first study is a sound study methodologically—except for the exposure estimates that are biased to increase the exposure-response slope of the study group of pre-1970 miners exposed to high and unregulated respirable coal mine dust levels. MSHA discusses the comments on bias in the exposure estimates in Section III.B.2.c of this preamble.

ER01MY14.001

Source: Reproduced from Table 7-3 of the NIOSH Criteria Document.

Similarly, the QRAs for the proposed and final rules focus on excess risk, rather than mean response, to show that respirable coal mine dust exposures for an occupational lifetime at the existing standard can significantly increase the risk of FEV

1

reductions associated with severe emphysema. Based on the exposure-response model described in Kuempel et al. (2009a), Figure 14 in both QRAs shows that among never-smoking white coal miners, the excess risk at 2.0 mg/m

3

ranges from approximately 12 percent (117 cases per 1,000) at age 65 to approximately 16 percent (162 cases per 1,000) at age 80. These percentages represent the estimated probability that a miner exposed to an average respirable coal mine dust concentration of 2.0 mg/m

3

over a 45-year occupational lifetime will develop severe emphysema attributable to that exposure.

The QRAs for the proposed and final rules use the pulmonary response model described in Kuempel et al. (2009a) as the basis not only for the estimates discussed previously, but also for the calculation of all current and projected excess risks of severe emphysema attributable to respirable coal mine dust exposures.

10

10

See QRA for the proposed rule, Tables 16, 24, and Appendix J.

Some commenters criticized the Kuempel et al. (2009a) study and the related study, Kuempel et al. (2009b) which relied on the same study population of 722 autopsied miners and non-miners. These commenters stated that the Kuempel et al. studies had little to no relevance to the existing or proposed dust standards because the exposures of the autopsied miners studied were pre-1970 and likely to have been much higher than current exposures. The commenters did not provide evidence to support their criticism of the Kuempel et al. (2009a and 2009b) studies.

Table 1 of the Kuempel et al. 2009b study and section 1(d)(ii) of the QRAs for the proposed and final rules show that the study group in question consisted of 616 deceased coal miners and 106 deceased non-miners (who presumably had no respirable coal mine dust exposure but functioned as internal controls in the statistical analysis).

11

Among the coal miners, the mean cumulative respirable coal mine dust exposure was 103 mg-yr/m

3

, with a standard deviation (σ) of 40.6 mg-yr/m

3

.

11

The commenters stated that the study population in Kuempel et al., 2009a “is comprised of 116 individuals with spirometry drawn from the same 722 autopsied miners and non-miners just discussed [in connection with Kuempel et al., 2009b].” In response to commenters, although 116 subjects with FEV

1

data were used to define cutoff points for clinically significant emphysema severity, the logistic regression models relating respirable coal mine dust exposure to the probability of meeting these cutoff points used all 342 members of the study population with complete data. (See Kuempel et al., 2009a, Tables 1 and 2).

Since miners in the study had an average tenure of 34.3 years, they were exposed to an average respirable coal mine dust concentration of 3.0 mg/m

3

(i.e., 103 mg-yr/m

3

/34.3 yr) over their occupational lifetimes, with σ = 1.184. Assuming an approximately lognormal distribution,

12

this would suggest that approximately 58% of these miners experienced average respirable coal mine dust concentrations less than 3.0 mg/m

3

and 19% of them averaged less than 2.0 mg/m

3

.

12

If X is Lognormally distributed with mean = 3.0 and standard deviation = 1.184, then Log

e

(X) is Normally distributed with mean = 1.026 and standard deviation = 0.380.

The QRAs for the proposed and final rules are designed to evaluate risks expected for exposures accumulated over a 45-year occupational lifetime. Therefore, it is also relevant to examine the distribution of respirable coal mine dust concentrations that would, after a 45-year occupational lifetime, give rise to the same exposure totals as those experienced by miners in the Kuempel et al. 2009b study. This result in an average respirable coal mine dust concentration of 2.3 mg/m

3

, with σ = 0.902 mg/m

3

. In this case, again assuming an approximately lognormal exposure distribution,

13

approximately 82% of the miners would experience average respirable coal mine dust concentrations less than 3.0 mg/m

3

, 43% would average less than 2.0 mg/m

3

, and 18% would average less than 1.5 mg/m

3

.

13

If X is Lognormally distributed with mean = 2.3 and standard deviation = 0.902, then Log

e

(X) is Normally distributed with mean = 0.756 and standard deviation = 0.380.

Consequently, considering either the 34.3-year average tenure of miners in the study group (Kuempel et al., 2009b), or the 45-year occupational lifetime MSHA uses to evaluate occupational risks, it appears that the Kuempel et al., 2009a, 2009b reports are relevant to exposure conditions under the existing respirable coal mine dust standard.

14

Table 8 of the QRAs for the proposed and final rules show that MSHA's enforcement of the existing respirable dust standard has not eliminated work locations exhibiting average respirable coal mine dust concentrations greater than 1.5 mg/m

3

or even 2.0 mg/m

3

. At the very least, these studies are highly relevant to risks at such work locations.

14

Since these studies used the same methods for estimating pre-1970 exposures as the NCWHSP studies, the comments on possible biases in these exposure estimates also apply here. Comments on bias in the exposure estimates are addressed in the Section III.B.2.c.

The commenters, in referring to the Kuempel et al. (2009a and 2009b) study population, identified self-reporting of smoking histories as a potential source of bias and rejected a suggestion by the studies' authors that the timing of self-reported data collection on smoking added to the studies' strengths. According to the studies' authors, data collection had occurred in the 1960s and 1970s, when smoking was not a contentious issue and Federal compensation programs for smoking-related illnesses had not yet been introduced. The commenters, however, contended that the authors' mention of possible smoking exposure misclassification “tends to negate” their claim that non-contentious smoking histories comprised a strength of the study. The commenters further argued that the studies' finding that dust exposure had a greater effect than smoking was unconvincing and that both of these factors were questionable for the study cohort because smoking histories were self-reported and “when compensation matters are involved, smoking histories are likely to be unreliable.” Commenters further stated that occupational dust exposure can have an effect on the development of emphysema and COPD, but the general literature still considers “ordinary” levels of occupational pollution to be minor compared to cigarette smoking and aging.

First, in response to commenters, as suggested by the studies' authors, MSHA points out that the reliability of the miners' smoking histories is unlikely to have been compromised by compensation programs in that the programs did not exist at the time of the studies. Kuempel et al. (2009a and 2009b) mention misclassification of smoking history only in a list of “potential limitations” and make no suggestion that this has anything to do with compensation incentives. Second, as demonstrated in the preceding discussion, respirable coal mine dust exposures for the autopsied miners were not “far in excess of today's standard”, 2.0 mg/m

3

, as the commenters state. Third, respirable coal mine dust exposure estimates were not biased to overestimate high exposures and underestimate low exposures. (See discussion in the subsequent preamble section on bias due to errors in exposure estimates, Section III.B.2.c.). Finally, the commenters interpreted the finding that each mg-year/m

3

of respirable coal mine dust exposure is, on average, similar in effect to each “pack-year” of cigarette

smoking as somehow undermining the studies' credibility.

15

The commenters did not provide any references to support their view that the general literature still considers adverse health effects of ordinary levels of occupational pollution to be minor relative to those from cigarette smoking; nor did they provide evidence that this generalization applies specifically to respirable coal mine dust and emphysema.

16

15

With regard to the probability of developing clinically relevant emphysema (i.e., emphysema associated with FEV

1

less than either 80% or 65% of predicted normal values, “the contribution of cumulative dust exposure was greater than that of cigarette smoking at the cohort mean values,

although not significantly so

. . . [emphasis added]” In the cohort used for the logistic regression analysis supporting this part of the analysis, mean cumulative respirable coal mine dust exposure was 87 mg-year/m

3

among miners and mea

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