Mining is a very unique, foundational industry upon which the vast majority of all other industries depend for raw materials. It has been a recognized, organized industry since the Bronze Age and today functions in one form or another in almost every country. The industry is populated by a wide variety of mine operators, from very small, independent mines with a handful of workers to some of the largest and most complex industrial operations in the world. Globally, millions are directly and tens of millions are indirectly employed by the mining industry. It is culturally unique in its audaciousness and confidence (to develop and operate mines), for its “salt-of-the-Earth” work ethic (a benefit and a challenge), and for its perception of and relationship to risk.
Similarly, the nature of mining risk is unique—in the diversity and potential magnitude of occupational health and safety hazards, and in the nature of the mining and mineral processing activities in which the hazards are encountered. There are myriad traditional and emerging health and safety issues to address, and the consequences of failure can be catastrophic. Mining is a serious business.
It also tends to attract gifted health and safety practitioners. Mining industrial hygienists and related professionals are most often successful because they possess or develop a unique mix of professional competencies to match the challenges of the industry. In addition to being technically competent in traditional health and safety management, industry practitioners must also have excellent communication skills, understand and manage complexity, handle physically challenging environments, and perhaps most important, be calibrated to the degree of change that occurs in every mine. DYNAMIC CHALLENGES Mining is by nature a dynamic activity. Even the orebody itself changes as it is mined, thereby altering the exposure and risk profile for those who work in proximity to the extraction and refinement processes. The percentage of hazardous components such as crystalline silica can vary widely within the same operation and can change rapidly and significantly. Thus, the mining process doesn’t lend itself to point-of-source controls, as is common in other industries.
The advent of autonomous equipment is changing that historical precedent, but while autonomous mining equipment is becoming more readily available, only a limited percentage of mining companies have the necessary resources or use mining methods that are amenable to such technology. As a result, most extraction continues using miners and equipment in very close proximity to the point of extraction. Enclosed mobile equipment cabs, general and local ventilation, dust suppression systems, and many other controls are common, but all systems developed for the industry—whether for exposure assessment or hazard controls—must factor the nature of change into their design. For example, the silica content within earthen materials can and does vary as the operation moves through different geologies. A silica exposure assessment may temporarily provide an industrial hygienist with an estimated exposure assessment, only for the percentage of silica content to change a week later.
For multinational mining companies the challenges often multiply as (regardless of legislative and regulatory requirements, and differences in language, customs, and cultures) most apply the same management systems across their global operations. Each operation, however, is often geographically isolated and very different from the next. While other industries may feel they have moved past the dynamics of traditional hazards, the mining industry continues to deal with these issues while simultaneously addressing novel emerging hazards. AIHA’S MINING WORKING GROUP AIHA has consistently recognized the importance of the mining industry. In August 2014, AIHA sanctioned the formation of a Mining Working Group (MWG). The MWG is a new professional venue for industrial hygienists, occupational medicine specialists, and safety professionals who work in and with the industry to network, share information, and advance the cause of protecting miners.
The Mining Working Group is the first significant effort in many years to focus and expand the global community of stakeholders who are interested in mining health and safety. Many practitioners who have worked in mining for years have relied on informal networks and unrelated professional groups to help them get things done and extend their knowledge. There is a sense today that we can do better by leveraging social media and networking, and in doing so mine the incredible amount of experience and knowledge that exists in the industry. The MWG intends to expand the horizons for industrial hygiene knowledge management in the mining industry.
Recently the MWG submitted comments in response to MSHA’s Request for Information (RFI) regarding controls for exposures to diesel exhaust in underground mines. Since the last rule change, publication of the Diesel Exhaust in Miners Study has linked diesel exhaust to lung cancer in miners. MSHA’s objective is to gather information regarding current diesel particulate matter (DPM) controls that may guide policy intended to further reduce miners’ exposures to exhaust with financially feasible controls. The MWG’s vision is to help develop a centralized body of knowledge of diesel exhaust control and exposure information, with the MWG’s members positioned to contribute exposure data linked to specific types of operation-level controls. The MWG’s team is considering multiple topics posed in the RFI, including current diesel emission levels from non-permissible, light-duty, diesel-powered equipment in underground coal mines; maintenance practices of diesel-powered equipment in underground coal mines that may or may not be effective in reducing various diesel exhaust exposures; alternative contaminants that could act as a surrogate for diesel exhaust exposure (as there are several confounding factors affecting the current surrogate, DPM); best practices that have proven effective in limiting DPM; and the greatest challenges faced while working to control diesel exhaust exposures.
The MWG’s comments on the RFI requested that MSHA help organize and coordinate a collaborative effort among interested parties to identify gaps in knowledge and develop a central repository of information regarding DPM exposures. We believe this issue is very large and complex, and will require a commensurate effort involving several national-level organizations.
The history of industrial hygiene is closely intertwined with the mining industry. Before the twentieth century, much of the theory and practice of occupational health focused on mining and mineral processing. For many years mysticism characterized industrial hygiene in the industry—it was even believed that illness-causing demons inhabited the mines.

Since the beginning of the twentieth century, many of the methods developed for evaluation and control of occupational exposures initially targeted the mining environment. Public perception and the importance of safety and health in mining were such that the United States Congress formed a unique regulatory administration, MSHA, to regulate the sector in 1977.
370 BC Hippocrates identifies lead poisoning in miners and metallurgists.

First Century AD
Pliny the Elder describes respirators made from animal bladders for use in mining.

1473 Ulrich Ellenborg publishes a pamphlet on the occupational diseases and injuries among gold miners.

1556 Georgius Agricola, a German scholar, publishes De Re Metallica, which describes every facet of the mining and smelting processes as well as diseases such as silicosis and accidents associated with the profession.

1567 Paracelsus, the “father of toxicology,” describes respiratory diseases and mercury poisoning among miners.

1665 The workday for miners is shortened in Idrija, Slovenia.

1700 The book De Mobis Artificum Diatriba by Bernardino Ramazzini, the “father of industrial medicine,” includes descriptions of the pathology of silicosis based on autopsies of miners’ bodies.

in Mining
New Control Technologies Hold Promise for Improvements in Health and Safety
DPM DATA Since 2000, MSHA has made detailed information regarding the occupational health exposure assessments performed during inspections available to the public. These data cover a range of exposure types found in the industry. According to data since the new diesel exhaust standard, DPM had a higher median exposure concentration-to-PEL (ECP) ratio (0.47) than any other airborne contaminant (for which 100 or more samples were taken) except silver fumes (0.88).
Median DPM ECP ratios vary widely by state. The state of Washington has the only median ECP ratio above 1.0 (1.22, based on 27 samples), followed by Virginia (0.98, 37 samples). Oklahoma (0.13, 24 samples) and Arkansas (0.15, 34 samples) had the lowest median ECP ratios. Of those counties with more than 10 samples, Okanogan County in Washington state (1.92, 20 samples) and Shasta County of California (1.56, 16 samples) had the highest median ECP ratios, while Sequoyah County in Oklahoma (0.13, 24 samples) and Rock Castle of Kentucky (0.14, 10 samples) had the lowest.
DPM exposures differ among mine type, mine size, and commodity sector as well. The worst median ECP ratios were observed at underground mines for copper ore (1.03, 71 samples, 207.6 million hours worked) and zinc (0.91, 170 samples, 610.5 million hours worked) mines. Where there were at least ten samples taken, underground stone (0.15, 47 samples, 84.6 million hours worked) and underground common clay (0.28, 18 samples, 6.2 million hours worked) mines had the lowest median ECP ratios for DPM. RISK AND COMPLAINCE-BASED APPROACHES The data clearly indicate a huge disparity in DPM compliance based on geography, mine type, mine size, and commodity sector, among several other factors. It is also obvious that much work remains to be done in controlling DPM exposures, given that nearly 50 percent of all DPM samples collected by MSHA are over 50 percent of the DPM PEL. While the MWG recognizes these issues, the unique nature of each mine and the factors that affect its safety and health have led some to question whether a “one-size-fits-all” approach is most appropriate or cost-effective at reducing injury and illness.
In the complex American regulatory system, the U.S. Department of Labor, through MSHA, publishes new regulations, standards, and operating requirements based on mandates from Congress and executive authority. Compliance with new safety and health regulations is mandatory for all mining facilities under MSHA’s jurisdiction. They represent the “do’s and don’ts” that mining companies must follow to legally operate and avoid civil and criminal penalties. This contrasts with Australia’s risk-based, “duty of care” regulatory structure implemented in New South Wales and Queensland in 2002 and 1999, respectively. The approach consists of three steps: a scoping assessment in which risks associated with specific operations are identified; a qualitative or semi-quantitative risk assessment that characterizes the magnitude of potential consequences and their likelihood, and outlines recommended controls; and a review of the recommended corrective actions, including an assessment of control efficiencies. Australia’s regulatory agency works with each mine site on all three steps.
It is conceivable that an approach targeting those mine sites with greatest risk of DPM overexposure may more efficiently utilize MSHA’s limited time and resources. A study published in Safety Science in 2008 found that, after implementing the risk-based approach, incident rate ratios of coal mining lost-time injuries fell by 52 and 72 percent in New South Wales and Queensland, respectively, compared to an 11 percent reduction in the U.S. over the same period. Making such a change in a country as large as the U.S. and in an industry as well-established as mining would require monumental efforts, resources, and data. While this is just one study evaluating a highly complex issue, a risk-based regulatory approach should be investigated and considered for the U.S. mining industry. CONTROLLING DIESEL EXHAUST EXPOSURES To control diesel exhaust exposures, options currently exist for every portion of the IH control hierarchy. Electrical equipment is becoming more common and may soon present a feasible, cost-effective solution for mining and other industrial settings. While newer diesel equipment doesn’t eliminate the risk of diesel exhaust exposure, it can result in exhaust reductions. Substitutions for diesel fuel, such as biodiesel or a natural gas/diesel blend called GDiesel, are being evaluated for their effect on diesel exhaust emissions. Generally, biodiesel has the potential to reduce DPM exposures but can actually increase others, as noted by a study published in the Journal of the Air and Waste Management Association in 2010. While less is known about GDiesel, a paper in the March 2015 Journal of Occupational and Environmental Hygiene suggests that it, too, has the potential to significantly reduce diesel exhaust exposures. Fuel additives can also improve fuel delivery and combustion, resulting in lower emissions, as shown by research published in the journal Topics in Catalysis.
Engineering controls include improved ventilation, as well as installation of exhaust after-treatment (EAT) systems, diesel oxidation catalysts, and diesel particulate filters. In addition, enclosed cabs with regularly changed particle filters can protect equipment operators from overexposure. Administrative controls consist of proper maintenance of engineering controls, such as EATs, as well as ensuring that the equipment’s fuel injection pressure is sufficiently high, fuel injector angles and timing are correct, and a sufficient amount of air is entering the engine chamber. While personal controls, such as air-purifying respirators, are an option, industrial hygienists should make every reasonable effort to maintain low diesel exposure concentrations. STRIDES IN SAFETY AND HEALTH Despite the dangerous nature of mining, significant strides have been made since passage of the Coal Mine Health and Safety Act of 1969 thanks, in part, to the tireless efforts of mining health and safety professionals. According to MSHA, mining fatalities in the U.S. averaged 426 per year from 1966 to 1970. Those numbers have dropped to an average of 38 per year during 2011–2016.
Mine safety and health is improving not only in comparison to historic data, but to other industries as well. According to the U.S. Bureau of Labor Statistics, the injury incidence rate for all of mining was 2.6 in 2014. This is lower than the incidence rates for the construction (11.7); educational and health services (11.6); public administration (10.4); trade, transportation, and utilities (9.3); agriculture, forestry, fishing and hunting (5.2); state government (3.8); manufacturing (3.6); and leisure, entertainment, and hospitality (3.5) industries for the same year. Though these data do not speak to the severity of injury, we are confident that mine safety and health is progressing—and the AIHA Mining Working Group is poised to help take it to the next level. TOM HETHMON, CIH, ROH, MAIOH, FAIHA, is head of HSE & CSR at KGHM International Ltd. in Vancouver, British Columbia, and past chair of the AIHA Mining Working Group. He can be reached at (801) 913-1660 or RUSTIN REED, MPH, is a doctoral student and industrial hygienist at the University of Arizona and the vice chair of the AIHA Mining Working Group. He can be reached at (520) 333-7585 or
Journal of the Air & Waste Management Association: “Aerosols Emitted in Underground Mine Air by Diesel Engine Fueled with Biodiesel” (February 2010).
Journal of the National Cancer Institute: “The Diesel Exhaust in Miners Study: A Cohort Mortality Study with Emphasis on Lung Cancer” (June 2012).
Journal of Occupational and Environmental Hygiene: “Occupational Exposures to Emissions from Combustion of Diesel and Alternative Fuels in Underground Mining-A Simulated Pilot Study” (March 2015).
Safety Science: “International Evaluation of Injury Rates in Coal Mining: A Comparison of Risk and Compliance-Based Regulatory Approaches” (October 2008).
Society for Mining, Metallurgy, and Exploration: Mine Safety and Health Management (2001).
Topics in Catalysis: “Ultra Low Dosage of Platinum and Cerium Fuel Additives in Diesel Particulate Control” (September 2001).
AIHA's Director of Government Affairs, Aaron Trippler, reported in October that OSHA is working on an updated compliance directive for workplace violence. The updated directive is expected to be released in February 2016.
Public support for legalizing marijuana has reached an all-time high in Gallup Polling with 58 percent of Americans supporting the movement. Last January, Fox News reported the stock price for a medical marijuana machine company increased 57 percent after Colorado legalized recreational use. The state reported over $5 million in taxed and regulated sales of marijuana during the first week of legalization and more than $200 million during the first four months. - Eric Nelson and Jeremy Slagley
The first definitions for respiratory protection terms appeared in a letter to the editor published in the December 1982 issue of the AIHA Journal. Alan Hack, Chuck Fairchild, and Barbara J. Skaggs of the Los Alamos National Laboratory Industrial Hygiene Group proposed definitions for four terms: Fit Factor, Protection Factor, Field Performance Factor, and Worker Use Factor. The letter noted that published industrial hygiene studies referred to "several different measurements of respirator efficiency or performance, with 'Protection Factor' being used to refer to each of them." A response from NIOSH staff in the March 1983 AIHAJ introduced additional terms, including Assigned Protection Factor.
For an explanation of the HSE/NPL test slide, see the article "The Phase Shift Test Slide Interpretation" (PDF) by OSHA's Daniel Crane and NIOSH's Martin Harper.
According to MSHA, in Fiscal Year 2016 (Oct. 1, 2015 through Sept. 30, 2016) there were 24 fatalities among mine workers in the U.S.—a record low, and a 30 percent decrease from FY 2013.