(April 16, 2024, 12:52 PM EDT) -- WASHINGTON, D.C. — The U.S. Department of Labor, through the Mine Safety and Health Administration, on April 16 announced an amendment to existing standards for miners establishing a uniform permissible exposure limit (PEL) for respirable crystalline silica at 50 micrograms per cubic meter of air (µg/m3) for a full-shift exposure, calculated as an eight-hour time weighted average (TWA) for all mines. The new standard reduces by half the current exposure limit....