Crushing rock and masonry material is a high dust activity that in the absence of controls would place workers at risk of lung disease, cancer, chronic obstructive pulmonary disease (COPD), lung scarring, silicosis, renal disease and autoimmune disorders, such as lupus and rheumatoid arthritis, with prolonged exposure. Silicosis is an incurable, sometimes fatal, disease. The NIOSH-recommended exposure limit is 0.05 mg/m3 as a time-weighted average concentration for up to a 10-hour workday during a 40-hour workweek. This is one-half of the OSHA standard when the dust is pure silica, but still twice the ACGIH-recommended threshold limit value of 0.025 mg/m3. Silica has also been associated with lung cancer and chronic obstructive pulmonary disease (COPD).