Asbestos
Why is Asbestos Significant?
- It is a known carcinogen
- It was widely used in the US in various products, such as building materials
- Ongoing asbestos abatement in buildings
- Current litigation issue
- The California State rock (serpentine)
Fate and Transport
- TERRESTRIAL FATE:
Movement of asbestos fibers only occurs during runoff or erosion. Asbestos fibers will not volatilize or degrade although they may be re-suspended to the air by vehicular traffic over unpaved soil surfaces containing asbestos or through mining and milling operations. - AQUATIC FATE:
Asbestos will degrade in water. - ATMOSPHERIC FATE:
Asbestos released to the air will eventually settle out by gravitational settling and dry deposition. In US cities, average concentration of 2-4 ng/cu m.
Historical Significance
- Due to some of its physical and chemical properties, asbestos has been mined, milled, and used in thousands of products in the US and abroad
- Egyptian burial cloths & Charlemaigne’s table cloth
- US Regulations starting in 1970’s
Where Can Asbestos be Found?
- Cement Pipes
- Laboratory Hoods/Table Tops
- Elevator Brake Shoes
- Cement Wallboard
- Laboratory Gloves
- HVAC Duct Insulation
- Cement Siding
- Fire Blankets
- Boiler Insulation
- Asphalt
- Floor Tile
- Pipe Insulation (corrugated air-cell, block, etc.)
- Fire Curtains
- Vinyl Floor Tile
- Elevator Equipment Panels
- Flexible Fabric
- Vinyl Sheet Flooring
- Caulking/Putties
- Cooling Towers
- Flooring Backing Adhesives
- Pipe Insulation
- Construction Mastics (floortile, carpet, ceiling tile, etc.)
- Wallboard Heating and Electrical Ducts
- Acoustical Plaster Joint Compounds
- Vinyl Wall Coverings
- Decorative Plaster Spackling Compounds
- High Temperature Gaskets
- Textured Paints/Coatings
- Roofing Shingles Roofing Felt
- Ceiling Tiles
- Thermal Paper Products
- Spray-Applied Insulation
- Fire Doors
- Electrical Cloth
- Blown-in Insulation
- Electrical Panel Partitions
- Fireproofing Materials
- Taping Compounds
- Electric Wiring Insulation
- Chalkboards
Adverse Health Effects
- Asbestosis (fibrous scarring of the lung)
- Lung cancer
- Mesothelioma (Very rare, and primarily associated with asbestos exposure)
- Gastrointestinal cancer
- A Significant elevation in the incidence of cancers of the larynx, pharynx and buccal cavity, and kidney
Physical and Chemical Characteristics
- Forms long thin fibers
- Tensile strength (matrix re-enforcement)
- Thermal & electrical insulation
- Sound insulation
- Non-flammable
- Adsorption capacity
- Wear & friction properties
Asbestos Chemical Structure
- Asbestos is a mineral composed primarily of silica, magnesium and water.
- Asbestos is classified as serpentines and amphiboles.
Types of Asbestos
-
Serpentine (Chrysotile)
It has a layered structure made up of SiO4 tetrahedral and Mg(OH)2 layers. The mismatch between those two types of layers is responsible for a curvature in the structure cylindrical/tubular form of the chrysotile fibres. The connections between the layers are weak, giving the chrysotile asbestos.
- Comprises majority of asbestos used commercially
- Can be woven into fabrics
Amphiboles
The amphibole structure is formed by double Si and O chains. The chains are connected by other elements like Na, Mg, Ca en Fe. Amphibole fibres have a diamond-shaped cross-section. They are less flexible than serpentine fibres, and they tend to split into small, very sharp splinters.
- Primarily used for thermal systems insulation (pipe lagging, etc.).
Toxicology of Asbestos
- Respiratory route is the most important
- Gastrointestinal and dermal routes less significant
- Once an asbestos fiber reaches the alveoli, it can become lodged in the lung for years.
- Some asbestos fibers can become dislodged from the alveolar wall, and be transported elsewhere
- Fibers can accumulate in the lung, and cause inflammation and scarring affects breathing, leading to disease = Asbestosis (10-30 year latency period)
- Lung Cancer (15-20 year latency period)
- Mesothelioma of the plura of the lungs or the peritoneum of the abdomen (20-40 year latency)
- Amphiboles remain in lung longer, and may therefore be more harmful
Pathology of Asbestosis
- Fibers retained in the lung are <3- 200 um
- A portion of the fibers become coated with an iron protein complex
- All types of asbestos cause microphage-mediated fibrosis. The areas increase in size and coalesce causing diffuse fibrosis with shrinkage.
- The process starts in the bases spreading upwards as the disease progresses; in advanced disease the whole lung structure is distorted and replaced by dense fibrosis, cysts, and some areas of emphysema.
Toxicology of Asbestos as a Carcinogen
Toxicology of Asbestos as a Carcinogen
- Lung Cancer
- Mesothelioma
Asbestos Mutagenicity
- Reactive Oxygen Species (Inflammation & macrophages)
- Size
- Shape
- Chrystallinity
- Solubility
- Distance between DNA & sources of ROS
- Oxide-reduction processes
- Iron reactivity
- Phagocytosis
- Altered Gene Expression
- Cell proliferation
Demonstration of Genotoxicity
- In-vivo chromosomal aberrations
- Impaired mitosis
- chromosome missegregation
- spindle changes
- alteration of cell cycle progression
- aneuploid and polyploid cells
- nuclear disruption
Asbestos-Related Lung Cancer
Mesothelioma development over time
"Historical" Target Occupations
- Asbestos textile mill workers
- Automobile workers and repairers
- Building material manufacturers
- Cement plant production workers
- Construction workers (including insulators, boilermakers, laborers, steel/ironworkers, plumbers, steam fitters, plasterers, drywallers, cement and masonry workers, roofers, tile/linoleum installers, carpenters, HVAC mechanics and welders)
- Electrical workers, including electricians, electrical linemen, and telephone linemen
- Miners
- Shipyard workers (including electricians, insulators, laborers, laggers, painters, pipefitters, maintenance workers, and welders)
- Custodians, insulation manufacturing plant workers, insulators, machinists, packing and gasket manufacturing plant workers, pipefitters, and powerhouse workers
- Railroad workers, steamfitters, refinery workers, sheetmetal workers, refractory products plant workers, rubber workers
- Aerospace and missile production workers, aircraft manufacturing production workers, and aircraft mechanics
Current Target Occupations
- Asbestos abatement workers
- Plumbers
- Electricians
- Construction workers/demo crews
- Miners (not US)
- Automobile repairers
Target Populations
- Families of occupationally exposed workers
- Persons living near asbestos mines
- Persons living in areas with asbestos-rich soils
- Persons occupying building with asbestos-containing materials (ACM) in poor conditions , or ACM being disturbed
- Persons located near such buildings
Additional Risk Factors
- Exposure: concentration what was the concentration of asbestos fibers?
- Exposure: duration how long did the exposure time period last?
- Exposure: frequency how often during that time period was the person exposed?
- Size, shape and chemical makeup of asbestos fibers
- Smoking!
- Estimates of 50% to 90x increased cancer risk (Synergetic)
- If a smoker has an asbestos exposure history, they can reduce their risk of developing an asbestos-related respiratory disease if they stop smoking.
Additional Risk Factors
- Not all ACBM must be removed
- The removal of ACBM is regulated and includes:
- Use of PPE
- Preparation of work site
- Construction of Containment & decontamination chambers
- Work to be performed under the supervision of a competent person
- Removal to be performed using wet methods
- Debris to be bagged and disposed of appropriately
- No visible emissions
- Post-cleaning
- Personnel Monitoring
- Clearance sampling must or should be conducted
- Post-removal strike-down, lockdown and application of substitutes
Personal Protective Equipment
- Safety/rubber boots
- Disposable protective clothing
- Head covering
- Leather gloves
- Hard hats
- Eye protection
- Respirator
- 1/2 face
- Full-face
- PAPR
- Supplied Air
Preparation of Work-Site
- Personnel records
- Sign-in sheets
- Lock-out/tag-out
- Pre-clean the room
- Remove contents from room and/or cover
Construction of Containment
Containment:
- Cover windows, doors, HVAC supplies and intakes, floor.
- Use 6-mil polyvinyl sheeting to construct containment
Decontamination Chambers Establish Area Post Signage
Debris to be bagged wet, and disposed of appropriately
Clearance Criteria
- ACM removed as necessary
- No debris/dust
- Passing air sample results:
- 0.01 fibers/cc PCM
- 70 structures/mm2 TEM
Replacement Agents
Product Type
- fabrics/papers
- Asbestos-containing cements/plasters
- Asbestos-containing break linings or disks
Fabrics/papers uses
- Insulation
- Pipe lagging
- Theater curtains
- Thermal systems insulation
- Beer/wine filters
Asbestos-containing cements/plasters uses
- Stucco
- Concrete
- Cement pipes
- Cement boards
Asbestos-containing break linings or disks uses
- Breaks
- Clutches
Replacement: fabrics/papers
- Fiberglass
- Synthetic
- Kevlar
- Ceramic
- Cellulose products
Replacement: Asbestos-containing cements/plasters
- Perlite
- Ceramic fiber
- Non-asbestos minerals
- Mineral wool
- Diatomacious earth & lime
Replacement: Asbestos-containing break linings or disks
- Synthetics
- Metallic fiber
- Glass fiber
Regulations: Federal Regulations
- EPA
- Asbestos Hazard Emergency Response Act under TSCA (AHERA, 40 CFR 763)
- Asbestos School Hazard Abatement Reauthorization Act under TSCA (ASHERA)
- National Emission Standards for Hazardous Air Pollutants under Clean Air Act (NESHAP, 40 CFR 61 part M)
- Clean Water Act (EPA 7 mf/l [million fibers/l])
- OHSA
- Construction Industry (29CFR 1926.1101)
- General Industry (29 CFR 1910.1001)
- Shipyard Workers (29 CFR 1915.1001)
AHERA
- Subpart E-Asbestos-Containing Materials in Schools
- Appendix A to Subpart E-Interim Transmission Electron Microscopy Analytical Methods-Mandatory and Nonmandatory-and Mandatory Section to Determine Completion of Response Actions
- Appendix C-Asbestos Model Accreditation Plan
- Appendix D-Transport and Disposal of Asbestos Waste
- Appendix E-Interim Method of the Determination of Asbestos In Bulk Insulation Samples
- Subpart G-Asbestos Worker Protection
- Subpart I (TSCA Ban)-Prohibition of the Manufacture, Importation, Processing, and Distribution in Commerce of Certain Asbestos-Containing Products; Labeling Requirements
- 1989 EPA announced ban and phase-down rule over 7 years to begin 1990.
- Use of asbestos products would have been banned in US, except products w/o substitutes and military use.
- 1991 Louisiana 5th Circuit Court of Appeals vacated regulation. Only 6 product categories subject to Ban & Phase-out rule:
- Result of TSCA Appeal Finding
- Products still subject to ban:
- Corrugated paper
- Roll board
- Commercial paper
- Specialty paper
- Floor felt
- New uses
- Products still subject to ban:
- Result of TSCA Appeal Finding
- Products not subject to ban:
- asbestos-cement corrugated sheet, asbestos-cement flat sheet, asbestos clothing, pipeline wrap,
- roofing felt, vinyl-asbestos floor tile, asbestos-cement shingle, millboard, asbestos-cement pipe,
- automatic transmission components, clutch facings, friction materials, disc brake pads, drum
- brake linings, brake blocks, gaskets, non-roofing coatings, and roof coatings
ASHARA
- Model Accreditation Plan
- Extends AHERA requirements to public and commercial buildings
NESHAP
- Protects the public by minimizing the release of asbestos fibers during activities involving the processing, handling, and disposal of ACM
- Notification requirements
- Work practices standard
- Zero visible emissions to outside air
- NESHAP Regs apply to removal of 260 LF or 160 SF of Regulated ACM
- Locally, NESHAP is enforced by S. Cal. Air Quality Management District.
NESHAP Product Bans
- Most spray-applied surfacing materials containing >1% asbestos (unless encapsulated, non-friable & no emissions)
- Fireproofing
- Decorative
- Thermal System Insulation
- Pipe insulation
- Insulation for boilers
OSHA
- Permissible Exposure Limit: 0.1 fibers/cc
- 30 min Excursion Limit: 1 fiber/cc
OSHA-General Industry
-
- Worker Protection
- Medical Surveillance
- Respiratory protection
- Work practices & engineering controls
- Personnel exposure monitoring
- Smoking cessation
- Bulk sample analysis
- Worker Protection
OSHA-Shipyard Workers
- Worker Protection
- Medical Surveillance
- Respiratory protection
- Work practices & engineering controls
- Personnel exposure monitoring
- Smoking cessation
- Bulk sample analysis
OSHA-Construction Industry
- Applies to:
- Demolition
- Renovation
- Maintenance/repair
- Emergency clean-up
- Transportation/disposal
- Does not apply to asphalt roof coatings, cement and mastics.
- Work area protection
- Worker protection
- Exposure assessments
- Negative Exposure assessments
- Engineering controls
- Work practices/housekeeping
State Regulations
- Cal/OSHA
- Construction Industry (CCR,Title 8, Section 1529)
- General Industry (Section 5208 of General Industry Safety Orders).
- Cal/EPA
- Department of Toxic Substance Control
Local Regulations
- local fire department
- County and city Ordinance
References
- http://www.epa.gov/asbestos/
- http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=9995
- http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=10862
- http://www.osha.gov/SLTC/asbestos/
- http://www.osha.gov/SLTC/constructionasbestos/
- http://www.atsdr.cdc.gov/asbestos/
- http://toxnet.nlm.nih.gov/cgi-bin/sis/search/f?./temp/~6EIoyw:1
- http://toxnet.nlm.nih.gov/cgi-bin/sis/search/f?./temp/~5JKyOO:1
- http://toxnet.nlm.nih.gov/cgi-bin/sis/search/f?./temp/~s0N5o1:1
- Roach, H. D, et al, “Asbestos: When the Dust Settles-An Imaging Review of Asbestos-related Disease,” Radiographics 2002;22:S167-S184.
- Schins, R. D, “Mechanisms of Genotoxicity of Particles and Fibers,” Inhalation Toxicology 2002; 14(1):57-78
- Jaurand, M. C, “Mechanisms of Fiber-Induced Genotoxicity,” Environmental Health Perspectives 1997;105:S5:1073-1084
- Barrett, J. C, Shelby, M. D, “Mechanisms of Human Carcinogens,” Progress in Clinical and Biological Research 1992; 374:415-434.
- McCrone, W. C, Asbestos Identification, G&G Printers, 1988
- NATEC Inernational, Inc., Asbestos Contractor Supervisor Refresher Course.
- California Code of Regulations, Title 8, Section 1529
- California Code of Regulations, Title 8, Section 5208