Mining Topic: Respiratory Diseases
What is the health and safety problem?
Miners are at risk of developing a lung disease called pneumoconiosis because of their regular exposure to airborne respirable dust, and miners with five or more years' mining experience who are exposed to exhaust from diesel engines have an increased risk of dying from lung cancer.
Pneumoconioses (meaning dusty lung) can cause impairment, disability and premature death. The two main types of pneumoconioses that affect miners are coal workers’ pneumoconiosis (CWP), commonly called black lung, and silicosis. CWP is associated with coal mining, but silicosis can affect workers in many types of mines and quarries, including coal mines. Medical treatment cannot cure these diseases, so preventing them – through controlling respirable dust exposure – is essential.
Exhaust from diesel engines has the potential to produce symptoms typical of asthma, and diesel exhaust exposure may contribute to other respiratory symptoms such as irritation of the nose, inflammatory changes in airways, and lung function decline.
Other respiratory diseases, such as chronic obstructive pulmonary disease (COPD), may also occur in miners separately from, or in addition to, pneumoconiosis.
What is the extent of the problem?
NIOSH, through the Coal Workers’ Health Surveillance Program (CWHSP), provides underground coal miners with an opportunity to have a chest x-ray on a periodic basis (approximately every five years) throughout their careers. The Respiratory Health Division of NIOSH manages this program and has compiled data since 1970 to track the prevalence of CWP in coal miners. As shown in the attached figure, the prevalence of examined miners with 25 or more years of mining experience that were diagnosed with CWP dropped from approximately 33% in the early 1970s to less than 5% by the late 1990s. However, since that time, CWP prevalence has increased to over 10% for the longest tenured miners. NIOSH also recently reported an unprecedented number of miners (416) were diagnosed with progressive massive fibrosis (PMF), which is the most severe form of CWP, when examined at three black lung clinics in Virginia. Through a special CWHSP program, NIOSH also examined over 2,200 surface miners from 2010-2011 and found 46 with CWP, 12 of which had PMF.
Graph of CWP respiratory disease in miners. (Click for larger image.)
From 2007 through 2016, CWP has been the underlying or contributing cause of death for 4,118 miners and a total of 75,178 miners from 1970 through 2016. More than $47.168 billion dollars in federal compensation has been paid to miners and their families from 1971 through 2019 for claims filed under the Black Lung Benefits Act.
Silicosis is not tracked as regularly or thoroughly as CWP but available historic data from the 1990s shows that over 23% of reported silicosis deaths were attributed to mining. Also, the change in disease profile for miners diagnosed with pneumoconiosis suggests that US coal miners are being exposed to more crystalline silica than in the past. This data shows a substantial increase over the last four decades in r-type opacities (associated with silicosis lung pathology) in the chest radiographs of miners, particularly for miners in the Central Appalachian region.
The Diesel Exhaust in Miners Study of more than 12,000 miners showed a significant increased risk of dying from lung cancer among miners who had ever worked underground. This risk increased as the miners’ exposure to respirable elemental carbon – representing diesel exhaust – increased.
How is the NIOSH Mining program addressing this problem?
Reducing miners’ exposure to respirable airborne contaminants directly reduces the risk of developing lung disease. Therefore, NIOSH Mining conducts research to identify sources of elevated respirable dust and diesel exposure and then identifies and evaluates engineering controls that can successfully reduce emissions from these sources. Control technologies and operating practices that can prevent airborne contaminants from reaching the breathing zones of workers are also researched. Another research goal is to develop sampling instrumentation that can provide mine worker and operators exposure information during or immediately after the working shift.
What are the significant findings?
NIOSH Mining has published resources for the mining industry to assist their effort to control dust and diesel exposure. These include Best Practices for Dust Control in Coal Mining, Best Practices for Dust Control in Metal/Nonmetal Mining, the second edition of the Dust Control Handbook for Industrial Minerals Mining and Processing, and Diesel Aerosols and Gases in Underground Mines: Guide to Exposure Assessment and Control.
NIOSH research produced a personal dust monitor that can provide an accurate measurement of airborne respirable dust immediately at the end of a mine workers’ work shift. The instrument also provides in-shift information that the worker can use to identify potential overexposures and then implement changes to reduce his or her exposure. This instrument was approved by NIOSH and MSHA for use as a continuous personal dust monitor (CPDM). As part of the 2014 MSHA dust rule, mine operators are required to use this instrument to measure dust exposure in underground coal mining operations to demonstrate compliance with the applicable dust limit.
To assist with the monitoring of respirable silica dust in coal mining operations, PMRD researchers have developed a sampling and field-based analytical technique that can quantify respirable silica levels at the mine site after sampling has been completed. A gravimetric sample is taken and the filter is placed in a portable FTIR sampling instrument that analyzes the sample. PMRD-developed software (FAST) interprets the instrument output and provides the silica content within a few minutes.
NIOSH has also developed a mobile video exposure monitoring method and software application (EVADE) that combines real-time exposure data with concurrently recorded point-of-view video to identify exposure sources for mobile workers.
NIOSH researchers identified factors affecting the protection from airborne dust by enclosed equipment operator cabs and published a method to estimate the protection afforded by an enclosed cab.
What are the next steps?
Ongoing research efforts to control airborne contaminants or develop sampling instrumentation include the following:
- investigating methods to optimize and maintain the performance of flooded bed scrubbers
- evaluating water spray and foam application for reducing coal and silica exposures on longwalls
- investigating the use of water-powered dust scrubbers on longwall shearers
- optimizing "smart" filtration and pressurization systems for enclosed work spaces
- investigating methods to lower exposure to welding fumes
- improving the field-based analysis technique for crystalline silica
- evaluating technologies to prevent diesel overexposures for high-risk occupations in M/NM mines
- evaluating advanced engine technologies for heavy- and light-duty underground vehicles
- evaluating advanced disposable filter elements for use in permissible diesel equipment
- evaluating enclosed cabs and canopy air curtains for controlling diesel aerosols
- examining past and current mining practices to identify potential factors related to elevated CWP levels
Additional information on current research efforts for controlling and monitoring airborne contaminants can be found through the link in the Fast Find box at the top of the page.
- Advanced Strategies for Controlling Exposures to Diesel Aerosols
- Advancing Exposure Monitoring for Airborne Particulates in Mining
- Best Practices for Dust Control in Coal Mining
- Best Practices for Dust Control in Metal/Nonmetal Mining
- Design, Testing, and Modeling of Environmental Enclosures for Controlling Worker Exposure to Airborne Contaminants
- Developing and Improving Respirable Dust Controls in Coal Mines
- Diesel Aerosols and Gases in Underground Mines: Guide to Exposure Assessment and Control
- Dust Control Handbook for Industrial Minerals Mining and Processing. Second edition.
- Emerging Respirable Dust Sensing and Control for M/NM Mining
- EVADE Software - 2.2
- Experimental Study on Foam Coverage on Simulated Longwall Roof
- Faces of Black Lung
- FAST - Field Analysis of Silica Tool - 1.0.3 Beta
- The Future of Respirable Silica Monitoring: Accurate Results Generated On-site in a Few Minutes
- Improving Protection Against Respirable Dust at an Underground Crusher Booth
- Investigating Mining Practices and Respirable Crystalline Silica Exposures in Underground Coal Mines
- Laboratory and Field Performance of a Continuously Measuring Personal Respirable Dust Monitor
- A New Leak Test Method for Enclosed Cab Filtration Systems
- Testing a Revised Inlet for the Personal Dust Monitor