The Mine Safety and Health Administration (MSHA) has proposed revisions to its respirable crystalline silica standard, including changes to exposure sampling, miner rotation, respirator use, medical surveillance, and how sampling results will be evaluated for compliance. The proposal would modify requirements established by MSHA’s 2024 final rule, which have so far been stayed by litigation and not enforced by the agency.
Join our MSHA team on Thursday, November 19 at 1:00 ET/10:00 PT for our live webinar discussion, where we will break down the changes, explain how the industry can participate in the rulemaking, and discuss compliance obligations.
Here are the key changes mine operators should be watching.
Core Provisions Remain Unchanged
Not everything has changed. Crucially, the Permissible Exposure Limit (PEL) of 50 µg/m3 and Action Level of 25 µg/m3 remain, as in the 2024 Rule. MSHA’s emphasis on engineering and administrative controls to control dust, rather than reliance on respirators, also remains unchanged.
MSHA continues to view this rule as a driver for engineering improvements and innovation in order to achieve compliance. While there was some relaxing on the use of administrative controls, the onus remains on operators to reduce or eliminate the sources of exposure rather than find administrative workarounds.
Miner Rotation Would Become an Available Compliance Tool
A potentially consequential change involves the rotation of miners.
Under the 2024 rule, rotation of miners was prohibited as an administrative control for complying with the silica PEL. MSHA now proposes to permit miner rotation as a method of compliance, providing more flexibility to operators. Importantly, though, rotation cannot be used as a corrective action after an overexposure. As such, implementing rotation following a sample result exceeding the PEL would remain impermissible.
Exposure Sampling Would Change Significantly
Perhaps the biggest day-to-day compliance changes involve silica sampling.
- Fewer miners would automatically fall within the sampling requirement
Sampling would be required for miners who may reasonably be expected to be exposed to silica at or above the action level. That is a change from the 2024 rule, which required sampling of miners who may reasonably be exposed to silica at all. Operators will need a sound exposure-assessment program for determining which miners could reasonably reach the action level.
- Initial sampling to comply with the rule would change
Operators would no longer be required to collect two samples below the Action Level to initially comply with the rule. MSHA proposes that operators continue to sample under a similar framework to the historic dust monitoring for Metal/Nonmetal, instructing operators to “conduct sampling as frequently as necessary”.
- Periodic (6-month) evaluation and post-evaluation sampling would be eliminated
MSHA proposes to eliminate the namely paperwork obligation of conducting and documenting an evaluation of the process and equipment to determine the potential exposure of miners above the Action Level. In the 2024 Rule, this obligation was to be completed regardless of whether there were any changes to the equipment, process, or geology of the mine site. Similarly, the NPRM would remove the obligation for post-evaluation sampling.
- Operators would still be required to submit to MSHA exposures of the PEL
A controversial requirement of the 2024 rule would remain should MSHA finalize the NPRM. MSHA has opted to continue to include that operators must notify the district manager (or a designated representative) if an operator sample comes back exceeding the PEL.
Medical Surveillance Obligations Would be Reduced
The proposal would also change the 2024 rule’s medical surveillance obligations. First, all mine operators, rather than only metal and nonmetal mines, would be required to provide certain medical examinations.
For metal and nonmetal operators, medical examinations that previously were mandatory for all miners new to the industry would instead become voluntary.
Mandatory medical examinations would be triggered only for miners whose exposure exceeds the PEL, as determined by an MSHA sample.
Noncompliance and Enforcement Guardrails are Clarified
In the rule, MSHA clarifies that noncompliance means an exposure above the PEL or above the action level. The rule also retains the requirement that operators must report exposures over the PEL to MSHA. The proposal does clarify that citations will be based on MSHA-collected samples above the PEL, suggesting that mine operators should not be cited based solely on reporting the results of their own sampling. We would expect to see quick follow-up sampling by MSHA to confirm overexposures if this proposal is finalized.
Sampling Results Would Drive Different Follow-up Obligations
The proposal would also change how operators should respond to the results of their own sampling.
- Below the action level: no follow-up sampling would be required.
- At or above the action level but below the PEL: respiratory protection would have to be made available before the miner’s next shift and maintained until sampling demonstrates exposure below the action level.
- At or above the PEL: additional corrective-action requirements would apply, and the overexposure must be reported to the MSHA District Manager.
- Following corrective actions: once sampling demonstrates exposure is at or below the PEL, the operator would have to contact the MSHA District Manager.
Respiratory Protection Programs Would Follow OSHA’s Standard
Another notable change involves the substance of respiratory-protection programs.
While the 2024 rule required respiratory protection programs to conform to certain ASTM provisions, the proposal would generally require compliance with OSHA’s respiratory-protection standard at 29 C.F.R. § 1910.134, subject to narrow exceptions involving oxygen-deficient atmospheres and recordkeeping. Mine operators would still follow MSHA’s applicable recordkeeping requirements.
For companies that also operate OSHA-regulated facilities, alignment with § 1910.134 may make respiratory-protection programs more familiar and easier to administer across operations.
Key Dates
MSHA has scheduled a virtual public hearing for December 15, 2026, beginning at 9:00 a.m. Eastern Time. MSHA will also accept public comments on the proposal through January 11, 2027. There is no fixed deadline for the agency to finalize the proposal, but stakeholders should expect the agency to take several months to review comments and complete the various stages of review before releasing the final rule.
MSHA has not announced an updated compliance deadline for the new proposal.
Our MSHA practice group will take a deep dive into the proposal in a live webinar on Thursday, November 19. Register now to join us, gain insights into what’s next in the process, and get real-time answers to your questions.
