If a haul truck driver’s silica exposure comes back above the federal limit in the 2024 rule, could the mine split the shift between two drivers to fix it? The Mine Safety and Health Administration’s November 12 proposal says no. It uses that example to explain when mine operators could still rotate workers.
The 2024 final rule set a limit of 50 micrograms of respirable crystalline silica per cubic meter of air over a full shift, calculated as an eight-hour time-weighted average. Its text barred rotation as a means of complying with the silica standards, though the agency explained at the time that the provision did not bar rotation for reasons such as cross-training. The new proposal would leave the limit in place and write the distinction into the compliance provision itself: Operators could not use rotation as a corrective action when a miner’s exposure exceeds the limit.
In the proposal’s explanation, routine rotation to limit noise or alternate strenuous tasks could continue. The agency draws a further line while a mine is correcting a silica overexposure: Operators could not start or expand rotation for another hazard if that could put more miners in conditions above the silica limit.
That language is still a proposal. In an April 2026 notice, MSHA said the U.S. Court of Appeals for the Eighth Circuit had stayed the 2024 rule’s compliance deadlines. The November proposal describes the stay as ongoing and does not lift it.
MSHA will hold an online public hearing on December 15. Written comments must be received or postmarked by midnight Eastern time on January 11, 2027. The notice’s filing instructions give docket number MSHA-2026-0200.