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A General Overview of 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

  • Movement of asbestos fibers only occur 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

  • Asbestos will degrade in water.

  • 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
  • aSignificant 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 Asbestos

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


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.
Asbestos Asbestos Asbestos

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
      • 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

Asbestos Asbestos
Asbestos Asbestos Asbestos
Asbestos Asbestos

"Historical" Target Occupations

  • Asbestos textile mill workers
  • Automobile workers& 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.

Asbestos Abatement

  • 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
Asbestos Asbestos

Construction of 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

Asbestos Asbestos Asbestos

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)


  • 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 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


  • Model Accreditation Plan
  • Extends AHERA requirements to public and commercial buildings


  • 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


  • 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

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


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