The PDM3600 and PDM3700 are two closely related person-wearable dust monitors manufactured by Thermo Fisher Scientific. Both are based on tapered element oscillating microbalance technology and provide nearly real-time, mass-based readings of respirable dust concentrations. From a monitoring perspective, the primary difference between the models is the PDM3600 has an integrated cap lamp with attached inlet, while the PDM3700 has no cap lamp and a revised inlet attaches to the worker’s lapel. Using coals of varied origin and employing a wide range of concentrations, side-by-side measurements from these instruments were collected under controlled laboratory conditions and then compared. By use of ordinary least squares and weighted least squares regression methods, followed by mixed model analysis, results suggest there is no statistically significant or practical difference in instrument performance. The two monitors are equivalent for the field dust concentration measurements for which they were designed. © This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply 2024.

The Mine Safety and Health Administration (MSHA) promulgated a rule in 2014 that required numerous changes in compliance dust sampling requirements for coal mine operators. Two key parts of this rule were the lowering of the respirable coal mine dust standard from 2.0 mg/m3 to 1.5 mg/m3 and requiring operators of underground coal mines to use a continuous personal dust monitor (CPDM) for compliance sampling. The CPDM currently approved for compliance sampling is equipped with a display that provides miners with in-shift information on their respirable dust exposure. The goal is to provide an indication of a potential overexposure and empower the miner and mine operator to implement changes in controls and/or operating practices to prevent an overexposure from occurring. Compliance sampling data for four occupations that have historically had elevated dust exposures were downloaded from the MSHA website and analyzed to assess the impact of the CPDM on overexposures. These occupations include continuous miner operator, roof bolter operator, tailgate-side shearer operator, and jacksetter. MSHA inspector and mine operator sampling data from five years before the rule became effective was compared to sampling results for five years after the dust standard was lowered and CPDM use was required. The analysis indicates that use of the CPDM has resulted in substantially lower percentages of samples exceeding the applicable respirable dust standard for these four occupations. A discussion of key dust rule changes, the CPDM, and compliance sampling results are provided. © 2022, This is a U.S. government work and not under copyright protection in the U.S.; foreign copyright protection may apply.

The canopy air curtain (CAC) has been proven to reduce the respirable dust exposure of roof bolter operators in underground coal mining. This technology is being adapted for use with shuttle cars and ramcars. The plenum is mounted on the underside of the shuttle car canopy over the operator’s position. The blower providing filtered air to the operator is plumbed into the shuttle car’s existing hydraulic system. After the system was installed on a ramcar, field testing of the CAC’s ability to provide respirable dust control was conducted on a section using blowing face ventilation. Results showed that overall respirable dust reductions during the total time the operator was underneath the canopy ranged from 11 to 34%, demonstrating adequate performance. However, further analysis demonstrated that the CAC performance was exceptional when the ramcar was being loaded by the continuous miner. At this location, a position where the shuttle car operator has their highest potential for respirable dust exposure, the CAC provided dust reductions ranging from 57 to 65%. These results, especially during ramcar loading at the CM, demonstrate that the CAC can be an important dust control device to reduce shuttle car and ramcar operators’ exposure to respirable coal mine dust. © 2022, This is a U.S. government work and not under copyright protection in the U.S.; foreign copyright protection may apply.

Coal workers’ pneumoconiosis (CWP), commonly known as black lung, is caused by the inhalation of respirable coal mine dust and is a disabling and potentially fatal lung disease with no cure. Historically, CWP has taken a tremendous human and financial toll in the US coal mining industry. Recent health surveillance data indicates that CWP continues to occur at elevated levels. Respirable coal dust exposure must be controlled to prevent the development of CWP. The Pittsburgh Mining Research Division of the National Institute for Occupational Safety and Health (NIOSH) conducts laboratory and mine-site research to identify control technologies that can be used to successfully reduce respirable dust levels. Various technologies, using multiple methods of control, can be applied in order to reduce dust levels. An overview of CWP’s impact and a general methodology for controlling respirable dust in underground coal mines are discussed in this paper.

In May 1994, the National Institute for Occupational Safety and Health (NIOSH) considered crystalline silica to be a potential occupational carcinogen as defined by the Occupational Safety and Health Administration's (OSHA) carcinogen policy [29 CFR 1990], and this information was used in establishing the NIOSH Recommended Exposure Limit (REL) at 50 micro g/m3. NIOSH has long realized that occupational overexposure to respirable crystalline silica (RCS) dust can lead to the development of silicosis, an incurable and often fatal lung disease, but it can also result in health problems that include chronic obstructive pulmonary disease, tuberculosis, chronic bronchitis, emphysema and chronic renal disease. Probably the most significant occupational travesty that brought focus to the effects of silicosis was the Hawk's Nest Tunnel Disaster in southern West Virginia where a 4.83-km (3-mile) tunnel was driven through the Gauley Mountain. The material being removed during the mining of this tunnel for the development of a hydroelectric power plant was a sandstone and limestone ore containing very high levels of crystalline silica. Within months of the completion of this work, 476 of the workers died from acute silicosis. This acute silicosis was caused by extremely high respirable dust concentrations while driving this tunnel and was attributed to inconsistent dust-control methods, including poor ventilation and minimal use of water, not allowing the dust to settle after blasting occurred before workers returned back inside the tunnel and no use of respiratory protection.

A sociotechnical system (STS) creates a framework that allows an examination of how social and technical factors affect organizational outcomes within a specific environmental context. STS has been rigorously studied with a primary research focus addressing worker-technology interactions. Although these interactions are important, the social processes and interactions that occur whenever any technical or environmental change is introduced into the system have been undervalued. If social processes are better understood, mining organizations could efficiently prepare and stabilize for such changes. With this goal in mind, we sought to extend STS theory through applying principles of meta-design to analyze the results of two case study interventions. Specifically, we studied the impact of an unregulated dust control technology (the Helmet-CAM) and a regulated dust control technology (the Continuous Personal Dust Monitor) on factors within an STS including employees' knowledge of, communication about, and use of technology to mitigate respirable dust sources. The results are presented in a way that first, addresses the overarching principles of meta-design STS including organizational participation, flexibility, and communication and second, examines how technology implementation processes differ when the organization is complying with a formal, higher-level requirement. Results show that a prominent focus on the social factors within an STS framework could help reduce unpredictability on the technical side and may improve communication within the system to help reduce adoption time, especially if and when accompanying a new, formal work process.

A person-wearable dust monitor that provides nearly real-time, mass-based readings of respirable dust was developed for use in underground coal mines. This personal dust monitor (PDM) combined dust sampling instrumentation with a cap lamp (and battery) into one belt-wearable unit, with the air inlet mounted on the cap lamp. However, obsolescence of belt-carried cap lamp and batteries in coal mining ensued and led end users to request that the cap lamp and battery be removed from the PDM. Removal of these components necessitated the design of a new air inlet to be worn on the miner's lapel. The revised inlet was tested for dust collection equivalency against the original cap-mounted inlet design. Using calculated inlet respirable fractions and measured dust mass collection, the performance of the two inlets is shown to be similar. The new inlet requires a 1.02 factor for converting dust masses obtained from it to equivalent masses collected from the original inlet.

After industrial sand has been mined and processed, the finished product is typically loaded into small bags of 45 kg (100 lb) or less, large bulk bags of 454 to 1,361 kg (1,000 to 3,000 lb), or vehicles such as trucks or trains for transport to end users. As the sand is being transferred and loaded, dust can be released into the work environment, potentially exposing workers to respirable crystalline silica. A number of control technologies have been developed and utilized in an effort to reduce dust liberation during loading operations. For bulk loading into trucks or trains, the U.S. National Institute for Occupational Safety and Health (NIOSH) evaluated one of these technologies, the Dust Suppression Hopper (DSH), at two industrial sand processing plants. Results from these case studies show that the DSH reduced airborne respirable dust levels by 39 to 88 percent, depending upon the product size being loaded.

OBJECTIVE: To characterize workplace practices and respiratory health among coal miners with large opacities consistent with progressive massive fibrosis (PMF) who received care at a federally-funded black lung clinic network in Virginia. METHODS: Participants were interviewed about their workplace practices and respiratory health. Medical records were reviewed. RESULTS: Nineteen former coal miners were included. Miners reported cutting rock, working downwind of dust-generating equipment, non-adherence to mine ventilation plans (including dust controls), improper sampling of respirable coal mine dust exposures, working after developing respiratory illness, and suffering from debilitating respiratory symptoms. CONCLUSIONS: Consistent themes of suboptimal workplace practices contributing to development of PMF emerged during the interviews. Some of the practices reported were unsafe and unacceptable. Further research is needed to determine the prevalence of these factors and how best to address them.

Continuous mining machines operating in U.S. underground coal mines have, for decades, utilized flooded-bed dust scrubbers for capturing and removing respirable dust generated at the production face. However, the application of dust scrubbers to longwall mining systems has not yet been successful. Considering that nearly 60% of U.S. underground coal production is from longwall mines, the successful application of dust scrubbers to longwall mining systems could have a significant impact on miner health. A full-scale mock-up of a longwall shearer was constructed and equipped with a flooded-bed dust scrubber designed to capture dust produced by the headgate cutting drum. The mockup was installed at the National Institute for Occupational Safety and Health (NIOSH) Longwall Dust Gallery and a series of 40 experiments was conducted to evaluate the scrubber's performance. Results show that the scrubber achieved a 56% reduction of respirable dust in the return airway and a 74% reduction of respirable dust in the walkway area near the shearer. Although these tests were conducted under a controlled environment, the results suggest that a similar scrubber design could be very effective at achieving a significant reduction in respirable dust in longwall mining systems.

In 2014, the Mine Safety and Health Administration (MSHA) enacted a new regulation, “Lowering Miners’ Exposure to Respirable Coal Mine Dust, Including Continuous Personal Dust Monitors” (30 CFR Parts 70, 71, 72, 75, and 90) that contained several progressive phases. One phase required mine operators to use a continuous personal dust monitor (CPDM) for compliance sampling, with another phase reducing the permissible exposure limit of respirable coal mine dust to 1.5 mg/m3 over the working shift. It has been more than one year since mine operations have had to use the CPDM.

Float coal dust is produced by various mining methods, carried by ventilating air and deposited on the floor, roof and ribs of mine airways. It deposited, float dust is re-entrained during a methane explosion. Without sufficient inert rock dust quantities, this float coal dust can propagate an explosion throughout mining entries. Consequently, controlling float coaf dust is of critical interest to mining operations. Rock dusting, which is the adding of inert material to airway surfaces, is the main control technique currently used by the coal mining industry to reduce the float coal dust explosion hazard. To assist the industry in reducing this hazard, the Pittsburgh Mining Research Division of the U.S. National Institute for Occupational Safety and Health initiated a project to investigate methods and technologies to reduce float ooal dust in underground coal mines through prevention, capture and suppression prior to deposition. Field characterization studies were performed to determine quantitatively the sources, types and amounts of dust produced during various coal mining processes. The operations chosen for study were a continuous miner section, a longwall section and a coal-handling facility. For each of these operations, the primary dust sources were confirmed to be the continuous mining machine, longwall shearer and conveyor belt transfer points, respectively. Respirable and total airborne float dust samples were collected and analyzed for each operation, and the ratio of total airborne float coal dust to respirable dust was calculated. During the continuous mining process, the ratio of total airborne float ooal dust to respirable dust ranged from 10.3 to 13.6. The ratios measured on the longwall face were between 1B.5 and 21.5. The total airborne float coal dust to respirable dust ratio observed during belt transport ranged between 7.5 and 21.8.

Controlling float coal dust in underground coal mines before dispersal into the general airstream can reduce the risk of mine explosions while potentially achieving a more effective and efficient use of rock dust. A prototype flooded-bed scrubber was evaluated for float coal dust control in the return of a continuous miner section. The scrubber was installed inline between the face ventilation tubing and an exhausting auxiliary fan. Airborne and deposited dust mass measurements were collected over three days at set distances from the fan exhaust to assess changes in float coal dust levels in the return due to operation of the scrubber. Mass-based measurements were collected on a per-cut basis and normalized on the basis of per ton mined by the continuous miner. The results show that average float coal dust levels measured under baseline conditions were reduced by more than 90 percent when operating the scrubber.

Airborne coal dust mass measurements in underground bituminous coal mines can be challenged by the presence of airborne limestone dust, which is an incombustible dust applied to prevent the propagation of dust explosions. To accurately measure the coal portion of this mixed airborne dust, the National Institute for Occupational Safety and Health (NIOSH) developed a sampling and analysis protocol that used a stainless steel cassette adapted with an isokinetic inlet and the low temperature ashing (LTA) analytical method. The Mine Safety and Health Administration (MSHA) routinely utilizes this LTA method to quantify the incombustible content of bulk dust samples collected from the roof, floor, and ribs of mining entries. The use of the stainless steel cassette with isokinetic inlet allowed NIOSH to adopt the LTA method for the analysis of airborne dust samples. Mixtures of known coal and limestone dust masses were prepared in the laboratory, loaded into the stainless steel cassettes, and analyzed to assess the accuracy of this method. Coal dust mass measurements differed from predicted values by an average of 0.5%, 0.2%, and 0.1% for samples containing 20%, 91%, and 95% limestone dust, respectively. The ability of this method to accurately quantify the laboratory samples confirmed the validity of this method and allowed NIOSH to successfully measure the coal fraction of airborne dust samples collected in an underground coal mine.

OBJECTIVE: To characterize exposure histories and respiratory disease among surface coal miners identified with progressive massive fibrosis from a 2010 to 2011 pneumoconiosis survey. METHODS: Job history, tenure, and radiograph interpretations were verified. Previous radiographs were reviewed when available. Telephone follow-up sought additional work and medical history information. RESULTS: Among eight miners who worked as drill operators or blasters for most of their tenure (median, 35.5 years), two reported poor dust control practices, working in visible dust clouds as recently as 2012. Chest radiographs progressed to progressive massive fibrosis in as few as 11 years. One miner's lung biopsy demonstrated fibrosis and interstitial accumulation of macrophages containing abundant silica, aluminum silicate, and titanium dust particles. CONCLUSIONS: Overexposure to respirable silica resulted in progressive massive fibrosis among current surface coal miners with no underground mining tenure. Inadequate dust control during drilling/blasting is likely an important etiologic factor.

The Code of Federal Regulations defines specific size and silica limitations for rock dust that is used in the underground coal mining industry. MSHA collected 444 grab samples of rock dust from mines located in Districts 2 through 11 and made these samples available to NIOSH for analysis. XRF and XRD analyses were completed on 261 rock dust samples, representing 23 producers and seven distributors. Results from the XRF analysis show that 93.5% of the analyzed samples meet the CFR requirement of containing 4% or less of FCS. Another 5.7% of the samples contained between 4.1 and 5% FCS, which can be approved for use by the Secretary of Labor. Consequently, only 0.8% of the samples analyzed contained FCS above the maximum allowable limit. Fifteen or more samples of rock dust were analyzed for six different producers. These samples were delivered to the mines in 40- or 50-lb bags or in bulk quantities. Comparison of the percentage of FCS and quartz content for the bagged and bulk products showed that these percentages were within 0.1% of each other for eight of 12 comparisons, with a maximum difference of 0.5% for FCS and 0.4% for quartz in the four remaining samples. Although not specified in the CFR, NIOSH was interested in quantifying the quartz content in the rock dust samples and had XRD analysis completed on these grab samples. Even though this analysis was not specifically conducted on the respirable fraction of the grab samples, the presence of rock dust continued quartz and a high respirable content would provide the potential for quartz inhalation by mine workers when exposed to airborne rock dust. A summary of these results showed that 97.3% of the samples contained less than 2% quartz. This quartz content is relatively low when compared to the 5% quartz level that must be exceeded in airborne respirable coal mine dust samples to result in a reduced respirable dust standard. However, size analysis of the rock dust samples showed that 87.7% of the samples contained over 20% respirable-sized dust, while 29.6% of the samples contained over 30% respirable dust. Not all of the respirable-sized dust in these samples will be present as airborne respirable dust when the rock dust is applied in mine entries. Nonetheless, mine operators should be aware of the potential exposure to respirable rock dust containing quartz and take steps to minimize or eliminate the time that mine workers are exposed to airborne rock dust. For workers required to apply the rock dust, it may also be appropriate for them to wear respiratory protection while completing this task.

Although rates of pneumoconiosis in coal miners have declined substantially in the United States since the passage of the Federal Coal Mine Health and Safety Act of 1969, new cases continue to occur, including cases of rapidly progressive disease. In contrast, Australia’s underground coal mining industry has reported few new cases of pneumoconiosis for more than 20 years. Mortality from coal workers’ pneumoconiosis in official health statistics and the prevalence of pneumoconiosis among miners screened in X-ray surveillance programs are also lower in Australia. The U.S. National Institute for Occupational Safety and Health (NIOSH) was requested by both industry and labor stakeholders to examine this issue, with the ultimate aim of reducing the rate of pneumoconiosis among U.S. coal miners. A number of factors, including coal dust exposure, silica exposure and coal rank were examined as potential contributors to the above noted differences. Comparison of coal rank data from each country did not illuminate the issue. Air sample data from the coal mining industries in both countries show that coal dust levels in Australian mines are somewhat higher than those reported in similar U.S. mines; however, quartz exposure for Australian miners is lower than for many U.S. miners. If quartz is contributing to the greater number of cases of pneumoconiosis in the United States, more effective dust control measures, as well as an independent exposure standard for respirable quartz in coal mining, should be implemented to reduce this potentially disabling condition.

Significant advances in longwall mining technology and equipment have occurred over the last decade. By the late 1990s, longwall mine output accounted for 40% of all underground output in the U.S. and today longwall mines account for approximately 50% of coal produced underground in the United States. A 51% increase in average shift production rates has occurred over the last 15 years. This increased longwall productivity has meant that far more dust is being produced and controlling respirable coal dust presents an ongoing challenge for coal mine operators. The National Institute for Occupational Safety and Health (NIOSH) conducted a series of benchmark surveys at longwall operations across the country to identify current operating practices and the types of controls being used. Gravimetric and instantaneous dust sampling was completed to quantify the dust levels generated by major sources on the longwall section and to identify different control technologies in use today. Substantial reductions in dust levels were realized at sampling locations on the face when compared with longwall surveys conducted in the 1990s. Results from the underground dust surveys and current longwall dust control technology and operating practices will be discussed.