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Silica Larry Joswiak, MPH March 31, 2010 Silica 1926.55 – Mineral Dusts • It’s not just dust…It’s silica • Silica NEP (National Emphasis Program) January 24, 2008 • Silica LEP (Local Emphasis Program) October 1, 2009 Targets specific General Industry SIC Codes What is silica? • Mineral – crystalline or amorphous forms – Crystalline most hazardous • Crystalline- 3 forms – Quartz, cristobalite, tridymite • Quartz – most common Major component of soils and readily found in rock Granite ~30% quartz Shale ~ 20% quartz Beach sand – nearly pure quartz Silica Exposure Activities • Sand/abrasive blasting • Tuckpointing • Jack hammering concrete • Brick/block cutting • Concrete cutting & drilling • Demolition • • • • • Stone cutting Foundry work Tunneling Rock drilling Quarrying What is silicosis? • A disabling and often fatal lung disease caused by breathing very small “respirable” particles of crystalline silica • >14,000 deaths since 1968 • >200 deaths each year in the U. S. Silicosis • Chronic/Classic – Occurs after 15 – 20 years of moderate to low exposure • Accelerated – Occurs after 5 – 10 years of high exposures • Acute – Occurs after a few months or as long as 2 years to extremely high concentrations Other Health Effects of Silica Exposure • Lung cancer – IARC Group 1: Carcinogenic to Humans • Tuberculosis • Chronic Obstructive Pulmonary Disorder – Bronchitis, Emphysema • Immunologic Disorders & Autoimmune Disease • Renal Disease • • Diseased and healthy lung Compare these sections cut from a diseased lung with large cavities (left) and a pink, healthy lung (right). The diseased lung shows a case of miner’s phthisis (also known as silicosis) which has led to tuberculosis. Quartz dust is inhaled by miners, and trapped in the lungs causes silicosis making the victim more susceptible to diseases such as tuberculosis and pneumonia. Current Respirable Silica Quartz Exposure Limits OSHA (PEL) Construction OSHA (PEL) General Industry 250 mppcf % silica + 5 10 mg/m3 % silica + 2 ACGIH (TLV) Quartz: 0.025 mg/m3 Cristobalite: 0.025 mg/m3 AIR SAMPLING EQUIPMENT Personal Air Pump with Cyclone PERSONAL SAMPLING OSHA Construction Industry a OSHA General Industry ACGIH Construction & General Industry Employee Name % Silica Time Sampled (minutes) 8 HR TWAa (mppcf)e PELb (mppcf)e 8 HR TWAa (mg/m3)d PELb (mg/m3)d 8 HR TWAa (mg/m3)d ACGIH TLVf (mg/m3)d Grinder 1 5.5 464 19.6 23.8 1.96 1.4 1.96 0.025 Grinder 2 4.5 474 20.2 26.3 2.02 1.54 2.02 0.025 Laborer1 3.6 463 3.5 29.1 0.35 1.79 0.35 0.025 Laborer 2 Air hose 3.8 478 5.7 28.4 0.57 1.72 0.57 0.025 8-hour Time Weighted Average Permissible Exposure Limit Employee exposure for time sampled d mg/m3 – milligrams per cubic meter of air b OSHA e mppcf c f TLV – million particles per cubic foot of air – American Conference of Governmental Industrial Hygienist’ Threshold Limit Values Concrete Cutting (Dry) Example • • • • • 6 % silica 2.27 mg/M3 PEL 16.3 mg/M3 (68 min) 2.31 mg/M3 8 hr TWA 8 hour severity 102% of PEL • EXCEEDED PEL • Gas saw dry cuts hole in concrete manhole • 718 % of PEL for 68 minute sample time 30% Crystalline Silica Quartz 10% Crystalline Silica Quartz 8 % Crystalline Silica Quartz 10% Crystalline Silica Quartz Silica Conclusions • Dry operations: High likelihood of silica dust overexposure • Wet operations: Low potential for silica dust overexposure • Exposures may be multiplied by factors such as interior workplace and corner location. Silica Conclusions • Written Hazard Communication Program – Employee training on silica • Engineering Controls – Use of water during cutting – Local exhaust ventilation • Respiratory Protection – NIOSH approved – Air Monitoring – Required or voluntary use • Eye Protection