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Respirable Crystalline Silica

Notice of Proposed Rulemaking

Occupational exposures to respirable crystalline silica may cause adverse health effects, including silicosis (acute silicosis, accelerated silicosis, simple chronic silicosis, progressive massive fibrosis), nonmalignant respiratory diseases (e.g., emphysema and chronic bronchitis), lung cancer, and renal disease. Each of these effects is chronic, irreversible, and potentially disabling or fatal. MSHA is proposing standards that would better protect miners from the potential health effects associated with exposure to respirable crystalline silica.

The proposed rule, Lowering Miners’ Exposure to Respirable Crystalline Silica and Improving Respiratory Protection, would set the permissible exposure limit of respirable crystalline silica at 50 micrograms per cubic meter of air (µg/m3) for a full shift exposure, calculated as an 8-hour time weighted average, for all miners. MSHA’s proposal also includes other requirements to protect miner health and updates the Agency’s existing respiratory protection requirements.

MSHA held three public hearings to give stakeholders the opportunity to present testimony, written comments, and other documentary evidence on the proposed rule.  The first hearing was held at MSHA headquarters in Arlington, Virginia, on August 3, 2023; the second in Beckley, West Virginia, on August 10, 2023; and the third in Denver, Colorado, on August 21, 2023.  A verbatim transcript of each of the hearings is available at MSHA’s website.

In addition to participation through public hearings, interested parties can provide comments on any aspects of the proposed rulemaking. The comment period on the proposed rule published in the Federal Register on July 13, 2023 was scheduled to end on August 28, 2023.  In response to requests for additional time to develop and submit comments on the proposed rule, MSHA extended the comment period for an additional 15 days to September 11, 2023.  The extension notice was published in the Federal Register on August 14, 2023.

Written comments must be received at by midnight Eastern Time on September 11, 2023. All submissions must include RIN 1219-AB36 or Docket No. MSHA–2023–0001.

  • Federal E-Rulemaking Portal:  Follow the online instructions for submitting comments.
  • Email:  Include “RIN 1219-AB36” in the subject line of the message. 
  • Regular Mail: MSHA, Office of Standards, Regulations, and Variances, 201 12th Street South, Suite 4E401, Arlington, Virginia 22202-5450.
  • Hand Delivery or Courier: MSHA, Office of Standards, Regulations, and Variances, 201 12th Street South, Suite 4E401, Arlington, Virginia, between 9:00 a.m. and 5:00 p.m. Monday through Friday, except Federal holidays.  Before visiting MSHA in person, call 202-693-9440 to make an appointment.  Special health precautions may be required.
  • Facsimile: 202-693-9441.  Include “RIN 1219-AB36” in the subject line of the message. 

Please see the links on the right-hand side of this webpage for more information on the rulemaking process and documents.