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Visual guide to asbestos risk assessment in buildings: This article discusses basic asbestos risk factors in buildings, simple visual inspection procedures, and summarizes current best judgment on removing versus leaving asbestos alone indoors. Visual inspection for asbestos is not a substitute for forensic investigation, air and dust sampling to detect asbestos contamination in buildings due to disturbance of that material. This is part of our document which assists building buyers, owners or inspectors who need to identify asbestos materials (or probable-asbestos) in buildings by simple
Also see ASBESTOS DUCTS, HVAC a field identification guide to
visual detection of asbestos in and on heating and cooling system ducts and flue vents.
Asbestos, a mineral fiber mined from the earth and used as a fire proof insulating material as well as in other products,
has been a major occupational and safety hazard of great concern since the 1930's.
Out of the work place, in homes and offices,
there are also potential health hazards, in particular if asbestos material is damaged, disturbed, in poor condition, or located where
it is likely to suffer these effects.
But often asbestos-containing
material can and should simply be left alone, undisturbed. Unnecessary disturbance of asbestos materials in such buildings
is at risk of creating a more severe hazard than leaving it alone. In other cases asbestos encapsulation may be recommended.
The decision to leave asbestos alone, encapsulate it, or removing asbestos depends largely on the type of material, its location, its condition,
and its exposure to
mechanical damage or fiber release. Comments at each example shown in this document indicate the reasons that further asbestos testing or removal are likely to
be needed or likely to be unnecessary.
Human exposure to airborne asbestos fibers has been linked to asbestosis and is a health hazard. Here is a series of photographs of places I've found common asbestos materials in buildings, and also where
I've found recognizable asbestos in a few surprise locations.
We also look at asbestos fibers in our forensic microscopy lab, but
we're addressing on-site visual inspection for asbestos here, not polarized-light microscopy such as our lab photo of crocidolite.
Curved asbestos fibers chrysotile. Straight asbestos fibers are amphiboles. The five amphiboles include amosite, anthophyllite, tremolite, actinolite,
crocidolite. Chrysotile is the most commonly-found asbestos fiber.
The carcinogenicity of asbestos varies according to fiber length and diameter. The most dangerous fibers were those longer
than 8microns and less than 1.5 microns in diameter.
Asbestos fibers shorter than 3-5 microns in length were reported to have
a very low, if any, carcinogenicity. (According to McCrone who in turn quoted studies by King, Klosterkotter, Hilscher, Davis Stanton, Pott, eta als.)
The Essential Asbestos Questions to Ask in Assessing the Asbestos Hazard Risk in a Building
Walter McCrone posed the following 5 key things that a building owner should know in deciding what to do about possible
asbestos in his or her building:
Are fibers present?
Are they asbestos?
If there are asbestos fibers present, in what proportion of the total?
What other substances are present (cellulose fibers, mineral wool, fiberglass, vermiculite, talc, perlite, pumice, diatomaceous earth, organic fibers,
clays, glass powder, quartz, calcite, gypsum (drywall dust), plaster dust, etc.) [some additions by DJF]
What is Friability (how easily are particles released into the air), effectiveness of existing isolation or encapsulation. [McCrone refers to asbestos materials which are friable - and so are more likely to be present in air, dust, or the environment. The floor tiles described by the box at left do not release high levels of asbestos fibers unless they are subjected to abrasion.
See ASBESTOS FLOOR TILE IDENTIFICATION for details. -- DF]
McCrone's five questions are focused on the examination of a particle sample, probably an air sample
of an indoor environment being tested for asbestos. Field experience suggests adding a 6th and a 7th question:
Is there obvious, visibly recognizable asbestos or asbestos-suspect material in
the building? (Some building materials are unmistakably asbestos or asbestos-containing and can be identified without lab analysis.
They are shown in photographs provided below.)
Is the asbestos friable? Perhaps re-stating #5 above in a compound question on friability: what is the general condition of the asbestos material?
Is it damaged and thus more likely to be friable? Is it in a location which is likely to move asbestos
particles into an occupied space by air movement or by human movement?
In effect, these questions assist in evaluating the potential asbestos hazard in a building. Simply looking at a snapshot of airborne
asbestos particles is very unreliable.
Our work examining airborne particles in a large number of buildings indicates that very significant
variations in the level of airborne particles (of all kinds) occur as a result of variations in normal building activity such as whether or
not people are even in the building, fans being turned on or off, windows open or shut, vacuuming of surfaces during "cleaning", etc.
"low" number in any airborne particle measurement is not, alone, reliable in characterizing building risk. [DF]
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Questions & answers or comments about making a visual determination of the level of risk based on the condition or nature of asbestos-containing materials in buildings.
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June 1997 - Window Putty - OSHA case cites contractor for asbestos exposure during removal of window putty http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=NEWS_RELEASES&p_id=1091
Asbestos Identification and Testing References
Asbestos Identification, Walter C.McCrone, McCrone Research Institute, Chicago, IL.1987 ISBN 0-904962-11-3. Dr. McCrone literally "wrote the book" on asbestos identification procedures which formed
the basis for current work by asbestos identification laboratories.
Stanton, .F., et al., National Bureau of Standards Special Publication 506: 143-151
Pott, F., Staub-Reinhalf Luft 38, 486-490 (1978) cited by McCrone
Asbestos in Your Home U.S. EPA, Exposure Evaluation Division, Office of Toxic Substances, Office of Pesticides and Toxic Substances, U.S. Environmental Protection Agency, Washington,D.C. 20460
Asbestos products and their history and use in various building materials such as asphalt and vinyl flooring includes discussion which draws on Asbestos, Its Industrial Applications, D.V. Rosato, engineering consultant, Newton, MA, Reinhold Publishing, 1959 Library of Congress Catalog Card No.: 59-12535 (out of print, text and images available at InspectAPedia.com).
"Handling Asbestos-Containing roofing material - an update", Carl Good, NRCA Associate Executive Director, Professional Roofing, February 1992, p. 38-43
EPA Guidance for Controlling Asbestos-Containing Materials in buildings, NIAST, National Institute on Abatement Sciences & Technology, [republishing EPA public documents] 1985 ed., Exposure Evaluation Division, Office of Toxic Substances, Office of Pesticides and Toxic Substances, U.S. Environmental Protection Agency, Washington,D.C. 20460
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
Or choose the The Home Reference eBook for PCs, Macs, Kindle, iPad, iPhone, or Android Smart Phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter INSPECTAEHRB in the order payment page "Promo/Redemption" space.