Back to the Drawing Board: MSHA Proposes to Rework Its 2024 Silica Rule
On November 12, 2026, the Mine Safety and Health Administration published a proposed rule in the Federal Register that would amend its 2024 respirable crystalline silica rule. The proposal keeps the permissible exposure limit (“PEL”) of 50 µg/m3 and the action level of 25 µg/m3, but would significantly change how operators sample, how MSHA enforces the PEL, and how respiratory protection and medical surveillance work. Comments on the proposed rule are due by January 11, 2027.
How Did We Get Here?
MSHA published the final 2024 rule on April 18, 2024. It cut the PEL to 50 µg/m3 for all mines, added sampling and corrective-action requirements, and required medical surveillance at metal/non-metal mines. Compliance was set for April 14, 2025, for coal operators and April 8, 2026, for metal/non-metal operators.
Industry groups, including the National Stone, Sand & Gravel Association and the National Mining Association, challenged the rule in the Eighth Circuit. On April 11, 2025, the court stayed the compliance deadlines pending review. MSHA has since paused enforcement of the rule, and in a status report to the court, said it would pursue limited rulemaking to reconsider portions of the rule. This proposal is the result.
What Would Change?
The most significant proposed changes are:
- A uniform 21% error factor and citations only on MSHA samples. MSHA would apply a 21 percent error factor to sample results, whether taken by MSHA or the operator, when determining compliance with the PEL and action level. MSHA would cite the PEL violations only on the basis of its own samples. MSHA reasons that its inspector samples are more consistent than operator samples, which can vary with the sampler, laboratory, and analytical method used.
- “As frequently as necessary” sampling. The fixed sampling schedule (including the 3-month interval and the ability to stop sampling after two consecutive results below the action level) would be replaced with a requirement to sample as frequently as necessary for miners who are or may reasonably be expected to be exposed at or above the action level. The 6-month periodic evaluation and post-evaluation sampling requirements would be eliminated. MSHA expects operators to re-evaluate and sample whenever conditions, processes, or procedures change, and it contemplates that operators may use objective data to decide whom to sample.
- Respirators at the action level. When a sample is at or above the action level but at or below the PEL, the operator would have to make approved respirators available before the next shift. Use by the miner would be voluntary.
- Rotation of miners. MSHA would clarify that the ban on rotation applies to its use as a corrective action when exposures exceed the PEL, not to rotation that is part of normal work practices. Operators could not add new rotation while corrective actions are ongoing.
- OSHA’s Respiratory Protection Standard. MSHA would replace ASTM F3387-19 with 29 C.F.R. § 1910.134, with two exclusions (IDLH altitude exceptions and OSHA’s medical-record retention period). It would also drop the word “temporary” from the metal/non-metal provision on respirator use above the PEL, allowing miners to work for “reasonable periods of time” in respirators while controls are developed or where the work requires it.
- Medical surveillance. Examinations for metal/non-metal miners new to the industry would become voluntary rather than mandatory, and the initial window for offering voluntary metal/non-metal examinations would expand from 12 months to 5 years. Mandatory examinations would be required for all sampled miners, coal and metal/non-metal, when an MSHA sample shows exposure above the PEL. The requirement to send x-ray classifications to NIOSH would be removed.
MSHA has also asked for comment on several open questions, including whether to adopt a different error factor, whether to exempt exposures from the mining and processing of sorptive clays, and whether to require mandatory examinations when an operator’s own sample exceeds the PEL.
What Does This Mean for Operators?
First, nothing is final. The 2024 rule remains stayed, and MSHA has said it will continue enforcing existing standards in the meantime. MSHA will hold a virtual hearing on December 15, 2026, and will accept comments through January 11, 2027. This is the time for operators to weigh in on the error factor, sampling practicalities, and the availability of NIOSH-certified B Readers.
Second, the proposal changes who bears what risk. Operators would no longer face a citation for noncompliance with PEL based on their own sample results, but their samples would still carry consequences. Under the proposal, a result above the PEL must be reported to MSHA and triggers corrective action, and a result at or above the action level triggers the respirator obligation. Operators should not treat the removal of the periodic evaluation as a reason to relax their silica programs. Under “as frequently as necessary,” the operator decides when to sample, and MSHA can second-guess that decision.
Third, expect this proposal to be tested from both directions. Section 101(a)(9) of the Mine Act bars MSHA from adopting a standard that reduces the protection afforded miners by an existing standard, and MSHA states that this proposal does not. Miner advocates and members of Congress have already criticized the proposal as weakening protections, so the “no-less-protection” analysis is likely to draw scrutiny in the final rule.
If you have any questions about how the proposed silica rule could affect your operations, or would like assistance preparing comments, please reach out to a member of the Jackson Kelly Workplace Safety and Health Team today. We are continuing to monitor this and other developments as they occur.