http://www.osha.gov/Publications/osha3176.html 2 million U.S. workers https://www.osha.gov/Publications/osha3176.html not safe to inhale inhaling silica carcinogenic dangerous silica exposure U.S. Department of Labor. 85% of workers dangerous Crystalline Silica Exposure Health Information OSHA silicosis [source] inhaling silica https://www.osha.gov/Publications/osha3176.html Crystalline Silica Exposure Health Information OSHA dangerous http://www.osha.gov/Publications/osha3176.html https://www.osha.gov/Publications/osha3176.html