FACT SHEET

Final Rule - Lowering Miners’ Exposure to 

Respirable Crystalline Silica and Improving 

Respiratory Protection

Overview

• To fulfill the Mine Act’s mandate to prevent death, illness, and injury from mining and 

promote safe and healthful workplaces for miners, MSHA has issued a final rule that

reduces miners’ exposures to respirable crystalline silica and improves respiratory 

protection for all airborne hazards. 

• Respirable crystalline silica (also known as silica dust or quartz dust) is a common 

occupational hazard for coal and metal/nonmetal (MNM) miners. Silica dust is generated 

by mining activities, including cutting, sanding, drilling, crushing, grinding, sawing,

scraping, jackhammering, excavating, and hauling materials that contain silica. Silica dust 

also mixes with other dusts created during mining, such as coal dust, to create increased 

risk of illness and death.

• Inhalation of silica dust, a carcinogen, puts miners at risk for developing illnesses that are 

chronic, irreversible, and potentially fatal, such as:

o Silicosis (acute silicosis, accelerated silicosis, chronic silicosis, and progressive 

massive fibrosis);

o Non-malignant respiratory diseases (e.g., emphysema and chronic bronchitis);

o Lung cancer; and

o Kidney disease.

• Exposure to mixed coal mine dust containing respirable crystalline silica can lead to the 

development of black lung disease and progressive massive fibrosis.

• The final rule reduces the permissible exposure limit (PEL) for silica dust to 50

micrograms per cubic meter (μg/m3

) of air; creates an action level of 25 μg/m3; establishes 

uniform exposure monitoring and control requirements for coal and MNM mines; creates

medical surveillance at MNM mines; and updates respiratory protection standards to better 

protect coal and MNM miners from exposure to all airborne hazards, including silica dust, 

diesel particulate matter, asbestos and other contaminants.

• MSHA will provide compliance assistance to the mining community (including industry 

and labor) through outreach workshops, virtual or onsite training, and the dissemination of 

best practice materials. MSHA staff from the Educational Field and Small Mine Services, 

Technical Support, and Mine Safety and Health Enforcement, working with the National 

Institute of Occupational Safety and Health (NIOSH), will assist mine operators and 

miners in implementing the final rule successfully.

Key Changes from the Proposed Rule

• Compliance dates extended: The final rule extends compliance dates to provide industry 

more time to plan and prepare for compliance with the new standards. Coal mine operators 

will have 12 months after publication, and MNM mine operators will have 24 months after 
publication to comply with the final rule.

• Exposure monitoring strengthened: Under the final rule, miners’ exposures to 

respirable crystalline silica will be monitored through recent sampling and qualitative 

evaluations; the final rule removes the option of using industry-wide objective data or 

historical sample data. The final rule strengthens periodic evaluations by adding a 

requirement that mine operators evaluate changes in the mining environment and their 

effects on miners’ exposure levels.

• Medical surveillance updated: The final rule clarifies the timing of voluntary and 

mandatory medical examinations provided to MNM miners. Additionally, the rule adds a 

requirement that mine operators ensure that medical providers will submit the results of 

chest X-rays to NIOSH, once NIOSH’s reporting system is established.

Final Rule

• Lowers the PEL for respirable crystalline silica: Under the final rule, the PEL for

respirable crystalline silica in MNM and coal mines is lowered to 50 μg/m3 for a full-shift 

exposure, calculated as an 8-hour time-weighted average (TWA), for all miners. If miner 

exposures are above the PEL, the mine operator is required to take corrective actions 

immediately and perform sampling until the exposures are at or below the PEL. In 

addition, mine operators are required to report all operator samples above the PEL to 

MSHA so the Agency is aware of the situation and can work with the mine operator to 

address the health hazard. 

• Establishes an action level for respirable crystalline silica: MSHA is also establishing

an action level for respirable crystalline silica of 25 μg/m3 for a full-shift exposure, 

calculated as an 8-hour TWA. When miner exposures are at or above the action level but at 

or below the PEL, the final rule requires mine operators to conduct periodic sampling until 

miner exposures are below the action level.

• Implements medical surveillance for MNM mines: The final rule requires MNM 

operators to establish medical surveillance programs under which the operators provide 

periodic health examinations at no cost to miners. This is similar to the medical 

surveillance program available to coal miners under existing standards. The new medical 

surveillance requirements will provide MNM miners with information needed for early 

detection of respirable crystalline silica-related disease.

• Updates the respiratory protection standard: MSHA is replacing its existing respiratory 

standard with the ASTM International 2019 standard entitled “Standard Practice for 

Respiratory Protection,” to help protect all miners exposed to respirable crystalline silica 

and other regulated airborne contaminants. The final rule will better protect miners who 

wear respirators.