1、A GUIDE TO WORKING WITH SILICAEnvironmental Health, Safety and Risk ManagementUniversity of Alaska FairbanksDecember 2010 1Overview Silica: crystalline vs. amorphous Part I: Crystalline Silica Health Hazards Exposure Limits Exposure Monitoring Ways to Reduce Exposure Online Resources2Overview (cont.
2、) Part II: Amorphous Silica Examples Exposure Limits Synthetic Vitreous Fibers Health Hazards Exposure Limits Engineering Controls Internet Resources3Silica Silica (SiO2, silicon dioxide) is one of the most common minerals in the earths crust and is a major component of sand, rock and mineral ores S
3、ilica is used in the manufacturing of a variety of products from kitty litter to fiber optic cables to cosmetics and food additives4Silica (cont.) Silica occurs as both crystalline (structured) and non-crystalline (amorphous) forms.5Diagram source: http:/www.osha.gov/SLTC/etools/silica/silicosis/sil
4、icosis.htmlPart I: Crystalline Silica6Silica: Crystalline Has a diagnostic X-ray diffraction* pattern *analytical technique which reveals information about the crystallographic structure, chemical composition, and physical properties of materials Most common types(formed under different pressures an
5、d temperatures) Quartz (alpha & beta) Cristobalite Tridymite7Silica, Crystalline,Health Hazards,Silicosis Silicosis is a disabling, nonreversible and sometimes fatal lung disease caused by overexposure to respirable* dust containing crystalline silica *respirable means deposited in the gas-exchange
6、region or deepest part of the lungs Overexposure to dust that contains respirable crystalline silica can cause scar tissue to form in the lungs, which reduces the lungs ability to extract oxygen from the air8Silicosis (cont.) Inhalation of crystalline silica particles has been associated with other
7、diseases, such as bronchitis, emphysema, and tuberculosis Some studies also indicate an association with lung cancer, immunologic disorders, autoimmune diseases, renal disease and stomach and other cancers9Silicosis (cont.) There are 3 types of silicosis: CHRONIC silicosis, which usually occurs afte
8、r 10 or more years of exposure at relatively low concentrations. This is the most common form of silicosis ACCELERATED silicosis, which develops 5 to 10 years after the first exposure ACUTE silicosis, which develops after exposure to high concentrations of respirable crystalline silica and results i
9、n symptoms within a period ranging from a few weeks to 5 years after the initial exposure 10Silicosis (cont.) Common symptoms shortness of breath following physical exertion severe cough fatigue loss of appetite chest pains fever cyanosis (bluish skin)11Silicosis: Who is at risk? Do you work in: con
10、struction mining, quarrying foundry work ceramics, clay, and pottery stone cutting glass manufacturing agriculture shipyards railroad manufacturing and use of abrasives (including sand blasting denim to “age” it!) dental laboratories manufacturing of soaps and detergents12Silicosis, Special Emphasis
11、 Program In 1996, OSHA established a Special Emphasis Program (SEP) for Silicosis, which provided guidance for targeting inspections of worksites with employees at risk of developing silicosis13Crystalline Silica, National Emphasis Program Effective January 24, 2008, OSHA implemented a National Emph
12、asis Program (NEP) to identify, reduce, and eliminate the health hazards associated with occupational exposure to crystalline silica Why? Because silica-related illnesses and fatalities continue to occur14National Emphasis Program (cont.) The NEP is a written compliance directive incorporating updat
13、ed information and policies and procedures adopted since 1996 Expands 1996 Special Emphasis Program Provides updated research results on silica exposure hazards15National Emphasis Program (cont.) Details inspection procedures, including follow-up inspections where overexposure found Addresses target
14、ing of worksites and provides updated NAICS (North American Industrial Classification System ) codes for industries with worker exposure to crystalline silica16National Emphasis Program (cont.) Explains calculation of PELS (Permissible Exposure Limits) in General Industry, Construction, and Shipyard
15、 Establishes program evaluation procedures Provides for Regional and Area Office outreach programs17OSHA Crystalline Silica Exposure Standards General Industry: 29 CFR 1910.1000 Construction: 29 CFR 1926.55(a) Shipyard: 29 CFR 1915.100018Crystalline Silica Exposure Limits, OSHA PELs OSHA regulates s
16、ilica exposure using the permissible exposure limit (PEL), which is the maximum amount of airborne dust an employee may be exposed to during a full work shift.The PEL is dependent on the % silica content of the dust from a sample collected over an 8 hour time period whether it is respirable or not t
17、he composition (quartz, cristobalite or tridymite)19Crystalline Silica Exposure Limits: Other Guidelines ACGIH (American Conference of Governmental Industrial Hygienists) Threshold Limit Value (TLV) for respirable quartz (alpha) and cristobalite:0.025 mg/m3 NIOSH (National Institute for Occupational
18、 Safety and Health) Recommended Exposure limit (REL) for respirable crystalline silica:0.05 mg/m320Crystalline Silica “Bottom Line” MessageThe more crystalline silica there is in the dust, the less of the dust you should breathe21Crystalline Silica: ExposureMonitoring Exposure monitoring (air sampli
19、ng) Measures worker exposures to respirable crystalline silica and helps select appropriate engineering controls and respiratory protection Monitors effectiveness of the controls Determines if exposures are in excess of permissible exposure levels (PELs) Performed when an employee is experiencing sy
20、mptoms or health effects that may be attributable to crystalline silica If you believe you need to have an exposure assessment conducted, contact EHS&RM at 474-6771 or 474-519722Ways to Reduce Exposure to Crystalline Silica: Engineering Controls Substitute materials that have no crystalline silica L
21、ocate employees as far as possible from dust-generation source Isolate employees OR the source Control rooms Enclosures Barriers23Ways to Reduce Crystalline Silica Exposure: Engineering Controls (contd) Use local exhaust ventilation (LEV systems) Use tools with dust-collecting systems Use wet method
22、s Cutting Chipping Drilling Sawing Grinding Clean surfaces with HEPA vacuums or wet sweepingno compressed air!24Ways to Reduce Crystalline Silica Exposure: RespiratoryProtection And if other controls are not sufficientUse Proper Respiratory ProtectionSource: NIOSH Publication No. 2004-108: Silicosis
23、: Learn the Facts! 25Ways to Reduce Exposure: Respiratory Protection (contd)Source: NIOSH Publication No. 2004-108: Silicosis: Learn the Facts!26Ways to Reduce Exposure: Respiratory Protection (contd) When respirators are used, the employer must establish a comprehensive respiratory protection progr
24、am, required in the OSHA respiratory protection standard (29 CFR 1910.134 and 1926.103) and as outlined in the NIOSH Guide to Industrial Respiratory Protection (NIOSH 1987a) The respiratory protection program should be evaluated regularly by the employer27Ways to Reduce Exposure: Respiratory Protect
25、ion (contd) Important elements of this standard are periodic environmental monitoring regular training of personnel selection of proper NIOSH-approved respirators an evaluation of the workers ability to perform the work while wearing a respirator respirator fit testing maintenance, inspection, clean
26、ing, and storage of respiratory protection equipment.28OSHA Internet Information on Crystalline Silicahttp:/www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=DIRECTIVES&p_id=3790http:/www.osha.gov/SLTC/silicacrystalline/index.htmlhttp:/www.osha.gov/dte/library/materials_library.html#silicawww.cdc.gov/niosh/topics/silicawww.cdc.gov/niosh/docs/2005-100/default.html29Part II: Amorphous Silica30
