OSHA particulate (not otherwise regulated) limit: 5 mg/m3 (respirable); 15 mg/m3 (total). This product contains trace quantities of naturally occuring radioactive uranium, thorium and radium «0.042% total). Overexposure by inhalation to respirable dusts containing uranium, thorium and radium may cause cancer, however, observance of the OSHA limit for respirable dusts of 5 mg/m3 will ensure the use of this product to be well below the regulatory limits established for these components.