or Permissible Exposure Limits are 0.
1mg/cubic meter over 8 hours. Stationary masonry saws without dust controls like wet sawing can generate 20 times this amount. With no respirator or dust controls, sufficient exposure for acute silicosis might result in as little as 4-6 weeks of 40 hours/week. Visible dust is no indicator since those particles are too large to reach lungs.