Presentation on theme: "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."— Presentation transcript:
Silica Larry Joswiak, MPH March 31, 2010
Silica – 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 ACGIH (TLV) 250 mppcf % silica mg/m 3 % silica + 2 Quartz:0.025 mg/m 3 Cristobalite:0.025 mg/m 3
AIR SAMPLING EQUIPMENT Personal Air Pump with Cyclone
OSHA Construction Industry OSHA General Industry ACGIH Construction & General Industry Employee Name % Silica Time Sampled (minutes) 8 HR TWA a (mppcf) e PEL b (mppcf) e 8 HR TWA a (mg/m 3 ) d PEL b (mg/m 3 ) d 8 HR TWA a (mg/m 3 ) d ACGIH TLV f (mg/m 3 ) d Grinder Grinder Laborer Laborer 2 Air hose a 8-hour Time Weighted Average d mg/m 3 – milligrams per cubic meter of air b OSHA Permissible Exposure Limit e mppcf – million particles per cubic foot of air c Employee exposure for time sampled f TLV – American Conference of Governmental Industrial Hygienist’ Threshold Limit Values
Concrete Cutting (Dry) Example 6 % silica 2.27 mg/M 3 PEL 16.3 mg/M 3 (68 min) 2.31 mg/M 3 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
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