US Department of Labor finalizes silica dust exposure limits for miners
Click Here to Manage Email Alerts
Key takeaways:
- In a full shift, miners cannot be exposed to more than 50 μg/m3 of respirable crystalline silica.
- Due to the damage silica dust does to the lungs, pulmonologists said this ruling was needed to protect miners.
The Mine Safety and Health Administration within the U.S. Department of Labor has finalized stricter limits on silica dust exposure for miners, according to a press release from the department.
Under this final ruling, the release states the maximum amount of respirable crystalline silica miners can be exposed to in a full shift is 50 μg/m3.
Other components of this ruling designed to protect the health of miners include use of engineering controls to stop overexposure, exposure monitoring via sampling and an updated standard that better protects against diesel particulate matter, asbestos and other contaminants in addition to silica dust.
According to the release, the final rule also encourages mine operators to begin free medical surveillance programs for miners in metal and nonmetal mines.
The Mine Safety and Health Administration (MSHA) website said June 17, 2024, will mark the first day this ruling goes into effect.
Healio spoke with two pulmonologists to learn more about the necessity of this ruling for miners and the clinicians treating them.
Drew A. Harris, MD, is associate professor of medicine in the pulmonary division at University of Virginia and medical director of the black lung clinic at Stone Mountain Health Services.
Lisa A. Maier, MD, MSPH, FCCP, is chief of the division of environmental and occupational health sciences at National Jewish Health and professor of medicine at University of Colorado, Denver.
Healio: Why is this ruling necessary to protect miners?
Harris: All miners are at risk for exposure to silica dust. Silica dust is toxic and causes a wide spectrum of diseases ranging from lung cancer, to increased susceptibility to specific infections, to chronic lung diseases (eg, emphysema, pulmonary fibrosis, pneumoconiosis). Even autoimmune diseases and kidney diseases have been associated with silica dust exposures.
Recent publications demonstrate that new diagnoses of progressive massive fibrosis (PMF) are at near-historical high levels in coal miners. PMF is a progressive and incurable chronic lung disease that is often fatal.
Multiple studies have shown that high rates of PMF in coal miners are driven be silica dust exposures in mines. Exposures to high levels of silica dust are a risk in any mine but are especially common in central Appalachian coal mines (due to regional mining conditions).
Maier: Unfortunately, we continue to see many patients with silica-related diseases including silicosis, mycobacterial infections and disease, and autoimmune diseases caused by silica exposure at National Jewish Heath. As a result, we have seen patients with various levels of lung disease severity, some severe enough that the silica exposure has resulted in lung transplantation.
My faculty at National Jewish Health has established local and regional clinics to screen workers with mining exposures for various diseases, including silicosis. These clinics evaluate patients in Colorado and the surrounding states, as well as in Arizona in the Navajo Nation for mining-related problems. However, these are not the only patients who end up with silica-related lung disease and are sent to our clinics. In Colorado not only do we have coal mines, but we have a number of other metal mines that have resulted in significant exposure to silica for those miners. Since silica levels were not controlled to a level that would have helped reduce disease, these patients often were exposed for many decades at very high levels and are now seeing the consequences of the exposure with a number of health effects.
Healio: How has the lack of rules on silica dust exposure negatively impacted public health?
Maier: While the Occupation Safety and Health Administration (OSHA) has more recently recognized that silica exposure needs to be regulated at lower levels and put a new standard in place a number of years ago to reduce exposures in the workplace, it was not until just now that MSHA put forth a similar standard for metal and nonmetal miners. As a result, medical and nonmedical miners have continued to have much higher levels of silica exposure in their workplace than would be allowed in others.
While the current standard will not help many of these workers who have been exposed at higher than acceptable levels for decades, it will help reduce the current workers’ cumulative exposures and certainly provide better protection than has been provided to miners to date.
Harris: High exposures to silica dust in coal miners often causes rapidly progressive and fatal disease. In my own black lung clinic, I have cared for many miners in their 40s and 50s with disease that literally takes their breath away. These are men raising children (or grandchildren) who have gotten a terrible disease simply because they showed up to work every day.
Healio: Why is this news important for clinicians who treat miners?
Maier: The diseases that silica causes are preventable. While we cannot reverse the damage that exposures over decades have caused, by reducing exposures in the workplace and in both metal and nonmetal mines (such as coal mines), this current standard should reduce and prevent disease from developing.
Our hope as health care providers is that we will start to see fewer cases of silica-related diseases in our respiratory clinics, as well as in our infectious disease clinics. Furthermore, we hope that we will not detect as many medical problems and diseases related to silica as we screen Coloradans and residents of the Far West for mine-related lung disease in our outreach clinics in the future.
These diseases are devastating and shorten people’s lives and this current standard should help improve exposures in all workplaces, including mines, and reduce the risk and/or prevent many of these diseases from developing for some current and future miners.
Harris: The current protections from silica dust are inadequate for miners. Until this regulation is enacted/enforced, miners are permitted to be exposed to double the amount of silica dust as any other American worker (eg, construction workers, countertop installers, etc).
This new regulation provides increased protection from silica dust for all U.S. miners. It reduces the maximum allowed levels of exposure to silica dust for miners to the same levels as all other workers in the U.S.
There are limited treatment options and no cures for my patients who have already developed severe disease due to mine dust exposures. However, if appropriately enforced, this new regulation has great potential to protect current and future miners from preventable diseases and mortality.
Reference:
- Respirable crystalline silica: Final rule. https://www.msha.gov/regulations/rulemaking/silica. Accessed April 16, 2024.