What you need to know about MSHA’s silica standard

By and |  July 7, 2023
Margo Lopez headshot 2022 Ogletree Deakins


Bill Doran


The Mine Safety & Health Administration’s (MSHA) silica rulemaking process has entered a significant new phase with the long-awaited issuance of a proposed rule: “Lowering Miners’ Exposure to Respirable Crystalline Silica and Improving Respiratory Protection.”

This is the first opportunity for mine operators to have any meaningful insight as to what direction MSHA may ultimately take with its new crystalline silica rule. Of course, this is only a proposed rule, and MSHA can make changes before issuing its final version.

In the meantime, nothing has changed in terms of what is required for compliance with the existing standard. Still, MSHA makes no secret of the fact that it has not been waiting for a new rule to increase enforcement activity for air contaminant standards – including silica – albeit under the requirements of the existing standards.

About the proposed rule

Photo: iStock.com/gobalink

The Mine Safety & Health Administration’s proposed rule on respirable crystalline silica would accept use of respiratory protection for compliance with the silica standard only “in limited situations and on a temporary basis, and to supplement engineering controls, followed by administrative controls.” Photo: iStock.com/gobalink

Here are the key elements of the proposed rule on respirable crystalline silica:

• Scope – The rule pertains to coal mines and all metal/nonmetal mines.

• Permissible exposure limit (PEL). As expected, MSHA intends to lower the PEL for silica to 50 micrograms per cubic meter of air for a full shift exposure, calculated as an eight-hour time weighted average. This is the same as the Occupational Safety & Health Administration’s (OSHA) current silica standard.

MSHA states that it considered lowering the PEL to 25 micrograms per cubic meter but concluded that not all mines could meet that level. MSHA wanted to maintain a single PEL that’s applicable to all mines.

• Action level. MSHA is proposing an action level for silica of 25 micrograms per cubic meter for a full shift exposure, calculated as an eight-hour time weighted average. If exposure monitoring indicates an exceedance of the action level, then the mine operator will be required to conduct periodic sampling.

• Exposure monitoring. The proposed rule includes extensive sampling requirements that operators may find to be overly burdensome. Baseline sampling would be required for most miners within 180 days of the effective date of the rule. Periodic sampling would be required unless baseline samples and other sampling data indicate no exposures above the action level.

Sampling must be repeated and verified in certain circumstances. Semi-annually, beginning 18 months after the effective date, every mine also must perform a qualitative analysis of any changes that may affect exposure levels.

• Engineering and administrative controls. The proposed rule would require mine operators to implement all feasible engineering controls to reduce respirable crystalline silica to at or below the PEL and then supplement those engineering controls with administrative controls, if needed to achieve compliance.

Administrative controls will only be accepted for compliance if all feasible engineering controls are already in place. Administrative controls include things such as ensuring miners safely remove dust from work clothes and controlling the ways certain types of cleanup and other tasks are done.

Importantly, MSHA would exclude the rotation of miners as an acceptable administrative control. This likely will generate comments in the rulemaking as operators may view this as an effective control where other options are not available.

• Respiratory protection. MSHA proposes to incorporate by reference certain elements of “ASTM F3387-19 Standard Practice for Respiratory Protection,” including fit testing, respirator selection, inspection and storage. This would apply to all of the agency’s airborne contaminant standards – not just the silica rule.

The proposed rule would accept use of respiratory protection for compliance with the silica standard only “in limited situations and on a temporary basis, and to supplement engineering controls, followed by administrative controls.” MSHA declined to accept respiratory protection for compliance under most circumstances. This is a significant departure from OSHA’s rule.

• No Table 1. MSHA has opted not to include a “Table 1” in its proposed rule, which would have specified control measures that would be considered acceptable for compliance for certain tasks. This is a critical departure from OSHA’s silica standard and something the industry advocated to be included.

• Medical surveillance for metal/nonmetal mines. The proposed rule will require mine operators at metal/nonmetal mines to offer medical surveillance at no cost to miners. The proposed rule does not include job transfer rights for miners as exist in 30 CFR Part 90 for coal, but MSHA is soliciting comments on whether this should be added for metal/nonmetal mines.

• Recordkeeping. The rule also contains detailed recordkeeping and reporting, which will impose substantial administrative requirements on operators.

• Effective date. MSHA proposes that the final rule become effective 120 days after its publication in the Federal Register. Operators may want to ask for this time to be lengthened in their comments, given the breadth of changes the rule will require.


In sum, MSHA’s proposed rule stands to impose significant administrative and technical requirements on operators and lacks several key provisions that would help operators maintain compliance while providing for appropriate protection of miners. Although the proposed rule is lengthy, operators may want to study it carefully and provide input to the rulemaking through the public hearings and written comments process.

Bill Doran and Margo Lopez are with the national labor, employment and safety law firm Ogletree Deakins. They can be reached at william.doran@ogletree.com and margaret.lopez@ogletree.com

Related: Poring over some of the latest mine safety statistics

Comments are closed