Mealey's (April 4, 2016, 9:42 AM EDT) -- WASHINGTON, D.C. — The U.S. Occupational Safety and Health Administration on March 25 announced a final rule amending its existing standards for occupational exposure to respirable crystalline silica after the agency said it realized that employees exposed to respirable crystalline silica at the previous permissible exposure limits “face a significant risk of material impairment to their health.”...