Mine Safety: Basis for Proposed Exposure Limit on Respirable Coal Mine Dust and Possible Approaches for Lowering Dust Levels
Published: 2014-04-09T00:00:00

Fast Facts:

Highlights:
section_title: Why GAO Did This Study
paragraphs: Underground coal miners face the threat of being overexposed to coal mine dust, which can cause CWP and other lung diseases, collectively referred to as black lung disease. In October 2010, MSHA—the federal agency responsible for setting and enforcing mine safety and health standards—proposed lowering the exposure limit for respirable coal mine dust to reduce miners' risk of contracting black lung. In August 2012, GAO reported that the evidence MSHA used supported its conclusion that lowering the exposure limit on coal mine dust would reduce miners' risk of disease. However, some have questioned whether and how recent NIOSH trend data on CWP were used in developing the proposed limit.
In May 2013, GAO was asked to provide additional information on MSHA's proposal. 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 level of dust in coal mines, including their associated advantages, disadvantages, and cost. GAO reviewed MSHA's proposal and related documents; updated a previous GAO literature search; interviewed MSHA and NIOSH officials; and, with the help of the National Academies, convened a group of experts knowledgeable about underground coal mining and methods for reducing coal mine dust. GAO is not making any recommendations in this report, and MSHA and NIOSH both generally concurred with the findings.
section_title: What GAO Found
paragraphs: The Department of Labor's Mine Safety and Health Administration (MSHA) appropriately did not use recent trend data on coal workers' pneumoconiosis (CWP) as a basis for its proposal to lower the permissible exposure limit for respirable coal mine dust. These recent data from the Department of Health and Human Services' National Institute for Occupational Safety and Health (NIOSH) are 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. MSHA primarily based its proposed new limit on two reports and six epidemiologic studies, which each concluded that lowering the limit on exposure to coal mine dust would reduce miners' risk of developing disease. MSHA's proposed coal mine dust limit was supported by these reports and studies because, unlike recent CWP trend data, they included information needed to conduct a reliable epidemiological analysis of disease risks associated with different levels of exposure to coal mine dust.
Experts identified various approaches that could incrementally reduce overall coal mine dust levels as well as individual miners' exposure to dust. They said that air and water are the primary engineering controls used to reduce overall coal mine dust levels in the mine environment, which are used in various mining equipment, such as sprays. The experts also said that no one technology or approach would result in substantially lower dust levels, but instead could have a cumulative impact if used together. They also noted that all the approaches may not be effective in all types of mines, and that there are a number of cost drivers that would have to be considered, such as machine maintenance and training. The experts also identified other approaches, such as personal protective equipment and administrative controls, which could reduce individual miners' exposure to dust. Personal protective equipment includes respirators and air stream helmets; administrative controls include rotating workers and using remote control devices. However, they noted that these approaches would not help mine operators comply with MSHA's exposure limit because they would not reduce the overall level of coal mine dust in the mine environment.

section_title: Letter
paragraphs: Coal mine dust is one of the most serious occupational hazards in the  coal mining industry, and overexposure can cause coal workers’  pneumoconiosis (CWP) and a number of other lung diseases collectively  referred to as black lung disease. CWP has been the underlying or  contributing cause of death for more than 75,000 coal miners since 1968,  according to the Department of Health and Human Services’ National  Institute for Occupational Safety and Health (NIOSH), the federal agency  responsible for conducting research on work-related diseases and injuries  and recommending occupational safety and health standards. Since  1970, the federal government has paid more than $45 billion in benefits to  miners totally disabled by respiratory diseases (or to their survivors),  including CWP, through the Black Lung Benefits Program.
In October 2010, the Department of Labor’s (DOL) Mine Safety and  Health Administration (MSHA)—the federal agency responsible for setting  and enforcing mine safety and health standards—proposed lowering the  existing concentration limit for respirable coal mine dust from 2.0  milligrams of dust per cubic meter of air (mg/m) to 1.0 mg/m In  commenting on the proposed rule, representatives of the coal mining  industry raised concerns about the feasibility and cost of reducing  respirable coal mine dust concentrations to the proposed limit of 1.0  mg/m Consistent with this requirement, in August 2012, we issued  a report in which we assessed the strengths and limitations of the data  and the analytical methods MSHA used to support its proposal to lower  the exposure limit for coal mine dust. In that report, we concluded that  the evidence MSHA used supported its conclusion that lowering the  exposure limit as proposed would reduce miners’ risk of disease.
In May 2013, you requested that we conduct an additional analysis of the  data MSHA used to support its proposal and provide information on  existing technologies that could be used to reduce dust levels in coal  mines. In this report, we address the following questions:  1.  To what extent did MSHA use recent CWP trend data as a basis for  its proposed exposure limit on coal mine dust?  2.  What are experts’ views on ways to lower the level of dust in coal  mines, including their associated advantages, disadvantages, and  cost? any additional recent studies on the prevalence of coal worker respiratory  diseases and reviewed additional information on the strengths and  limitations of CWP trend data. To gather experts’ views on the options  that exist to lower the level of dust in coal mines and their associated  advantages, disadvantages, and cost, we worked with the National  Academies to convene a group of experts that included mine operators,  equipment manufacturers, researchers, and other stakeholders. For  more details on our scope and methodology, see appendix I. We  conducted this performance audit from July 2013 to April 2014 in  accordance with generally accepted government auditing standards.  Those standards require that we plan and perform the audit to obtain  sufficient, appropriate evidence to provide a reasonable basis for our  findings and conclusions based on our audit objectives. We believe that  the evidence obtained provides a reasonable basis for our findings and  conclusions based on our audit objectives.
subsections: section_title: Background
paragraphs: Inhaling excessive amounts of coal mine dust can cause CWP and other  debilitating lung diseases, including chronic obstructive pulmonary  disease, which encompasses chronic bronchitis and emphysema.  According to NIOSH, it usually takes about 10 to 15 years of exposure to  coal mine dust to develop CWP, although cases involving fewer years of  exposure have been observed. Once contracted, CWP cannot be cured,  making it critical to prevent the development of this disease by limiting  miners’ exposure to coal mine dust.
MSHA is responsible for protecting miners by enforcing the provisions of  the Federal Mine Safety and Health Act of 1977 (Mine Act), as amended.  Under this law, MSHA has a number of responsibilities, including setting  new safety and health standards and revising existing standards,  approving training programs for mine workers, and developing regulations  regarding training requirements for rescue teams, among other things.
MSHA also conducts periodic inspections of coal mines and, along with  coal mine operators, periodically collects samples of coal mine dust to  determine compliance with the exposure limit. MSHA set the current  exposure limit for coal mine dust at 2.0 mg/m. This limit applies to the  overall level of dust in the mine environment; specifically, it provides that  each mine operator “shall continuously maintain the average  concentration of respirable dust in the mine atmosphere during each shift  to which each miner in the active workings of each mine is exposed” at or  below that level. To measure the level of dust in the mine environment,  MSHA requires that mine operators collect samples of dust in specific  areas of the mine and for designated occupations. Designated  occupations are those that have the greatest concentration of coal mine  dust, as determined through MSHA sampling. then took effect.  Pub. L. No. 91-173, § 202(b), 83 Stat. 742, 760-61 (1970). The 1977 Mine Act did not  change the 2.0 mg/m. 45 Fed. Reg. 23,990,  24,001 (Apr. 8, 1980) (codified at 30 C.F.R. § 70.100). incurring any disability from… occupation-related disease during or at  the end of such period.”
NIOSH shares some responsibility with MSHA for improving mine safety  and protecting miners’ health. For example, NIOSH conducts research on  the causes of work-related diseases and injuries; researches, develops,  and tests new technologies and equipment designed to improve mine  safety; and recommends occupational safety and health standards, such  as the exposure limit for coal mine dust. NIOSH also administers the Coal  Workers’ X-ray Surveillance Program—a medical monitoring and  surveillance program designed to detect and prevent lung disease. This  program requires mine operators to provide up to three initial chest x-rays  for coal miners within specified time frames after their employment  begins. Miners then can opt to have periodic chest x-rays approximately  every 5 years thereafter. NIOSH uses this program for disease  surveillance, which includes tracking trends, setting prevention and  intervention priorities, and assessing prevention and intervention efforts.  In addition, to estimate the prevalence of lung disease among  underground coal miners and to study the relationship between miners’  lung disease and their level of exposure to coal mine dust, NIOSH  developed the National Study of Coal Workers’ Pneumoconiosis. In this  study, NIOSH collected and analyzed epidemiological data—including  findings from chest x-rays, results of lung function tests, and occupational  and smoking histories—from a sample of coal miners across all major  coalfields in the United States between 1969 and 1988. The data also  allowed researchers to link to results of coal mine dust sampling over  approximately the same period to estimate dust exposures for individual  miners. According to NIOSH, epidemiological studies examining the  relationship between coal mine dust and disease must contain a  sufficiently large body of data over a time period that is adequate to  derive reliable findings.
There are two primary types of underground coal mining in the United  States: continuous mining and longwall mining. In continuous mining, a  machine called a continuous miner cuts out rooms of coal from the coal  bed leaving a series of pillars of coal to help support the mine roof. In  addition to the pillars of coal, bolts are driven into the roof of the mine to  help support the mine. The extracted coal from the continuous miner is  loaded into shuttle cars for transport out of the mine. In longwall mining, a  machine called a shearer moves back and forth across a wall of coal.  After the coal is cut, a machine crushes it into small pieces and a  conveyer belt removes it from the mine. While the shearer cuts the coal  and the coal is extracted, the roof is held up temporarily with self- advancing hydraulic supports. While both types of mining produce dust,  certain pieces of machinery produce more coal mine dust than others. For  example, in continuous mining, the continuous miner, roof bolting  machines, and shuttle cars generate the most dust. Major sources of dust  in longwall mining include the shearer and crusher.
section_title: MSHA Did Not Use Recent CWP Trend Data as a Basis for Its Proposed Exposure Limit on Coal Mine Dust, Which Was Appropriate
paragraphs: Appropriately, MSHA did not use NIOSH’s surveillance data as the basis  for its proposed new coal mine dust limit, although the data served to  inform MSHA’s decision to take action. In the preamble to its proposed  rule, MSHA cited an increase in the prevalence of CWP among  underground coal miners based on NIOSH surveillance data, which may  have led many to believe that these data were part of the basis for  MSHA’s proposed change in the exposure limit. The surveillance data  showed that the prevalence of CWP, which declined substantially  between 1970 and the late 1990s, increased for several years in the early  2000s before declining again between 2005 and 2009. According to  MSHA and NIOSH officials, information about the increasing prevalence  of CWP based on the surveillance data was mentioned in the preamble to  the proposed rule to show that black lung disease still exists among  active underground coal miners, thus helping to compel MSHA to take  action to reduce miners’ exposure to dust, in accordance with its duties  under the Mine Act. However, as we reported in August 2012, the data  MSHA used to support its proposal were from two reports, which relied on  six epidemiological studies, not the surveillance data. In addition, in a  1996 notice in the Federal Register, well before the increase in the  prevalence of CWP shown by the surveillance data, MSHA stated its  intent to respond to a 1995 NIOSH recommendation to lower the  exposure limit for coal mine dust by developing a proposed rule. dust because of some important limitations of the data. For example,  because the data do not include individual miners’ past exposures to coal  mine dust, they cannot be used to estimate disease risk for individual  miners. Based on principles of epidemiology and statistical modeling,  measures of past exposures to coal mine dust are critical to assessing  the relationship between miners’ cumulative coal mine dust exposure and  their risk of developing CWP. Also, because there is no active selection of  miners by researchers and participation in the surveillance program is  voluntary, miners who choose to participate may differ in unknown ways  from those who choose not to participate, which could result in an  overestimation or underestimation of the prevalence of disease. This  methodological limitation is known as participation bias, and there are  many ways it could affect the prevalence of disease indicated by the  surveillance data. For example, the prevalence of CWP could be  underestimated because some miners may decline further x-ray  screenings once CWP is detected. Alternatively, the prevalence of CWP  could be overestimated because miners may be more likely to participate  after years of dust exposure, when they believe they are at risk of  developing CWP.
section_title: Experts Identified Various Approaches that Could Reduce Overall Coal Mine Dust Levels, as Well as Individual Miners’ Exposure to Dust
subsections: section_title: Experts Identified Various Engineering Controls That Could Help Reduce Overall Coal Mine Dust Levels
paragraphs: Experts identified various engineering controls that could further reduce  the overall level of coal mine dust, but they said reductions would likely be  incremental. Since 1968, the mining industry has achieved significant  reductions in the level of dust in underground coal mines. Average dust  levels declined from about 7 mg/m in 1968 to below 2 mg/mreplace contaminated air with fresh air, which also helps reduce the level  of coal mine dust in the air.
The experts also described ways that operators use water to prevent dust  from being generated in mining operations. For example, operators spray  water on the surface of the coal and on the machines’ cutting surfaces as  the coal is being cut to reduce the amount of dust generated. In some  cases, operators also infuse water into the coal prior to cutting, but the  experts reported limited success with that approach. Operators also use  hygroscopic salts on mine floors to help maintain the moisture content of  the mine floor, which in turn absorbs coal mine dust. The experts said  that, with the increased productivity of mines in recent years, the water  quantity and pressure for sprays may need to be increased. From 1978 to  2007, the amount of coal produced per work hour has more than tripled.  The experts cautioned, however, that using too much water could have  adverse impacts, such as causing conveyor belts to slip, which would  affect production.
The experts pointed to a number of factors that could limit mine operators’  use of engineering controls aimed at reducing coal mine dust in the mine  environment. The experts said that fundamental differences between  continuous mining and longwall mining operations render some  technological approaches useful for one type of mining, but not both. For  example, while scrubbers were cited as an effective tool for reducing dust  in continuous mining operations, the experts cautioned that they may not  be as effective for mines that require a lot of ventilation, such as longwall  mines, because the amount of air flowing through the mine can  overwhelm the scrubber. An expert noted that one way to reduce dust  levels is to operate only one continuous mining machine at a time in a  section of a mine instead of more than one. However, he estimated that  this could significantly decrease the productivity of the mine and increase  the cost of producing the coal. Another expert noted that controlling dust  in a cost-effective manner requires some flexibility.
The experts did not quantify the cost of some of the technologies used in  reducing dust levels because dust control is not the only purpose of some  of the technologies, and future technologies have not been developed  enough to fully determine their costs. However, they did identify primary  cost drivers. For example, mines that contain high levels of gas must  ventilate significant amounts of fresh air, which also helps lower coal mine  dust levels. They also noted that while NIOSH has done some of the  major research on dust control, overall, industry research on dust control  technologies has declined. One expert made the point that research is  directly proportional to the economic health of the coal industry. When the  industry is contracting economically, manufacturers may not be willing to  devote resources to research and development. While specific costs were  difficult to assign, the primary drivers the experts identified for lowering  dust levels were the cost of maintaining equipment; the cost of  purchasing new or additional equipment, materials, and labor; and the  cost of providing training.
section_title: Experts Noted Options That Could Reduce Individual Miners’ Exposure to Dust
paragraphs: The experts identified options that could reduce individual miners’  exposure to respirable coal mine dust, specifically, personal protective  equipment and administrative controls. However, they noted that these  options would not help mines reduce the overall level of coal mine dust in  the mine environment, and therefore would not help mine operators  comply with MSHA’s exposure limit. Personal protective equipment  includes items such as respirators and air stream helmets. Respirators  filter the air that an individual miner breathes and air stream helmets  actively filter and push air across a miner’s face. While respirators and air  stream helmets could reduce the amount of coal dust to which individual  miners are exposed, the experts noted that miners have concerns that  these devices limit communication between miners and thus could raise  safety issues. The experts also said that personal dust monitors could  be used to reduce individual miners’ exposure to dust because they  provide workers with real time data on dust levels in the area of the mine  in which they are working. This information allows workers to adjust their  position in the mine to reduce their exposure to coal mine dust. Although  personal dust monitors have no effect on dust levels in the mine, the  experts noted that they may provide data that could be used by mine  operators to identify problem areas in the mines and to change work  practices to reduce miners’ exposure to coal mine dust. One of the  experts told us personal dust monitors cost about $13,000 to $18,000 per  unit, which could be a significant expense if all miners were outfitted with  them.
The experts also noted that administrative controls could limit miners’  exposure to coal mine dust, although they do not control the overall level  of dust in the mine. These controls include rotating workers more  frequently from positions that are exposed to higher levels of dust, cutting  the coal using a remote control device, and changing the sequence by  which coal is cut. Experts said that rotating workers to other positions  could help reduce their exposure to dust, but this could also require  changes to the current collective bargaining agreement at unionized  mines because the jobs that involve highest exposure to dust may also  pay more. This approach may also increase costs for mine operators  because, for example, the collective bargaining agreement might require  them to continue to pay workers a higher rate of pay when they rotate to a  lower paying position. The experts also said that some mines use remote  control devices to keep miners farther away from the source of dust.  Controlling the mining machine from a greater distance than is currently  done may require high resolution imaging equipment. One expert said  that this is especially true for mining operations where geologic conditions  change frequently, requiring miners to make judgments about where to  move the machinery. According to the experts, another way to limit  exposure to individual miners in continuous mining is by modifying the  sequence in which coal is mined. The experts explained that this  approach reduces the number of miners who are downwind from the dust  generated by the continuous mining machine. However, this type of  change could result in decreased productivity in the mine.
section_title: Agency Comments
paragraphs: We provided a draft of this report to the Secretaries of Labor and Health  and Human Services for review and comment. Both agencies generally  concurred with the findings of the report, but provided no formal written  comments. The agencies did, however, provide technical comments,  which we incorporated as appropriate.
We are sending copies of this report to the appropriate congressional  committees and the Secretaries of Labor and Health and Human  Services. In addition, the report is available at no charge on the GAO  website at http://www.gao.gov. If you or your staff have any questions  about this report, please contact me at (202) 512-7215 or   moranr@gao.gov. Contact points for our Offices of Congressional  Relations and Public Affairs may be found on the last page of this report.  GAO staff who made key contributions to this report are listed in appendix  II.
section_title: Appendix I: Objectives, Scope, and Methodology
paragraphs: The objectives of our review were to: (1) determine the extent to which  the Mine Safety and Health Administration (MSHA) used recent coal  workers’ pneumoconiosis (CWP) trend data as a basis for its proposed  exposure limit on coal mine dust, and (2) obtain experts’ views on ways to  lower the level of dust in coal mines, including their associated  advantages, disadvantages, and cost.
To address our first objective, we reviewed MSHA’s Notice of Proposed  Rulemaking, including the proposed exposure limit and related  documents, updated the literature search from our prior report, and  interviewed officials from MSHA and the National Institute for  Occupational Safety and Health (NIOSH) to identify recent data on the  prevalence of coal worker respiratory diseases. Two GAO research  methodologists and one public health specialist reviewed information  gathered about CWP trend data, to assess its strengths and limitations,  and reviewed a recent study by NIOSH researchers on the usefulness of  these data for estimating disease prevalence. We also reviewed our prior  report and the analyses that supported it, and interviewed MSHA and  NIOSH officials to determine what role, if any, recent CWP trend data had  in developing the proposal to lower the exposure limit. We examined  whether these data would have been appropriate for MSHA to use in  developing its proposed exposure limit using principles of social science  research and epidemiology.
For our second objective, we worked with the National Academies to  convene a group of experts to obtain their views on these issues. To  prepare for our discussions with experts, we reviewed NIOSH and other  studies on the ability of currently available and alternative technologies to  control coal mine dust. We also reviewed the technological and economic  feasibility assessments MSHA used to develop its proposed exposure  limit. The group included experts from all of the major stakeholder groups:  NIOSH researchers, academics, other technical experts, individuals from  companies that manufacture mining equipment, and individuals who  represent coal mine operators and workers. In identifying the experts, the  National Academies compiled a preliminary list of 53 experts who  represented 17 universities, 7 coal companies or coal associations, 5  equipment manufacturers, 1 mine workers’ association, and 2  government agencies. The nominees were grouped by sector and field of  expertise, and were vetted by 10 individuals working in the public, private,  and academic sectors who have expertise in coal mining or a related  field. Feedback from these individuals, along with biographical information  about the experts, was used to prioritize the experts within each sector  and field of expertise. Using this information, we invited 17 experts to  participate in a 1-day panel discussion, although 1 person subsequently  cancelled. The resulting 16 experts included 3 representatives of mine  operators, 1 representative of underground coal miners, 3 representatives  of equipment manufacturers, 6 academics, and 3 representatives of  federal government agencies.
To ensure that there were no unforseen biases or conflicts of interest,  each panelist reported to the National Academies his or her investments,  sources of earned income, organizational positions, relationships, and  other circumstances that could affect, or could be viewed to affect, his or  her view on the topic of methods for reducing the level of respirable dust  in underground coal mines. We asked the experts to discuss the  technological and other options available for lowering the level of dust in  coal mines below the existing permissible exposure limit and the costs,  advantages, and disadvantages of these technologies. We did not ask the  experts about the proposed new limit. In addition to the 16 panelists, we  allowed 5 observers to sit in on the panel discussion. The observers  included representatives of mining equipment manufacturers, coal mine  operators, and one government agency.
We conducted this performance audit from July 2013 to April 2014 in  accordance with generally accepted government auditing standards.  Those standards require that we plan and perform the audit to obtain  sufficient, appropriate evidence to provide a reasonable basis for our  findings and conclusions based on our audit objectives. We believe that  the evidence obtained provides a reasonable basis for our findings and  conclusions based on our audit objectives.
section_title: Appendix II: GAO Contacts and Staff Acknowledgments
subsections: section_title: Contact
paragraphs: Revae Moran, (202) 512-7215 or moranr@gao.gov.
section_title: Staff Acknowledgments
paragraphs: In addition to the contact listed above, individuals making key  contributions to this report were Mary Crenshaw (Assistant Director),  Nabajyoti Barkakati, Russell Burnett, Sarah Cornetto, Andrea Dawson,  Timothy Guinane, Kristy Kennedy, Kathy Leslie, Sheila McCoy, Sara  Pelton, Tim Persons, Martin Scire, Sushil Sharma, Walter Vance,  Kathleen van Gelder, and Shana Wallace.