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There are a wide variety of methods utilized to test for and then analyze samples thought to be Asbestos Containing Materials. At Adelaide Environmental Health Associates, we have significant experience with all of the following.
Phase Contrast Microscopy (PCM) - because of its fast turnaround time and relatively low cost, PCM is widely used to gauge the fiber concentration within air samples. This method is routinely used at asbestos abatement sites and is suitable for environmental monitoring, personnel monitoring, and clearance testing for most abatement projects in New York City and New York State.
A light microscope technique operates at magnifications of 400X and will resolve fibers larger than 0.25 microns in diameter. PCM is not utilized to distinguish asbestos fibers from other fibers (ex: gypsum, mineral wool, fiberglass, cellulose etc.), but rather to give an overall reading of various types of fibers present in the sample.
As such, a PCM analysis indicating high fiber counts does not necessarily indicate the presence of asbestos nor low fiber counts indicate an asbestos free environment. PCM merely provides an index of the total airborne fibers present in a given size range. If fibers smaller than 0.25 microns (um) needs to be identified, and/or fiber type needs to be differentiated, the use of TEM is required.
Transmission Electron Microscopy (TEM) - the most sophisticated technology available for characterizing asbestos minerals, this technique has become standard for most airborne investigations including post abatement clearance testing, testing in schools and certain larger projects in NYC and New York state as well as diagnostic and environmental monitoring activities.
Using magnifications of 19,000X or greater and enabled by chemical and mineralogical additives, TEM can differentiate asbestos from non-asbestos fibers and also classify the several species that comprise asbestos minerals. More process-intensive, the sample preparation and analysis timing makes this process longer, in general, than that of PCM.
Bulk Building Materials
The analysis of Bulk Building Materials for asbestos content is most often initially conducted by Polarized Light Microscopy (PLM), and less frequently utilizing Transmission Electron Microscopy (TEM).
Polarized Light Microscopy (PLM) - the most widely-used approach for the analysis of bulk building materials, this technique utilizes the unique features of polarized light to observe mineral-specific optical properties. PLM can differentiate asbestos from non-asbestos fibers and also classify the various species that compose the asbestos mineral family.
The PLM approach provides an economical technique for screening large numbers of samples. That said, there are limitations to light microscopy testing due to the magnification employed (100-400X) and to interferences sometimes present in the building material sample. For example, tar and petroleum binding components might adhere to and obscure the surface of the asbestos mineral.
Transmission Electron Microscopy (TEM) - referenced in the Airborne section above, TEM is often used to confirm the presence or absence of asbestos in non-friable bulk samples following inconclusive results by PLM. As stated, electron microscopy is capable of detecting the smallest asbestos fibers, its magnification levels of up to 19,000x are perfect for sample types such as those found in fine dusts and highly-milled asbestos.
Non-friable Organically Bonded Materials - (NOBs)
These are asbestos containing materials (ACM) which, in general, are more resistant to crushing or pulverizing because they are bound in asphalt, vinyl or some other bonding agent. These include building materials, sealants and adherents found throughout private and public buildings: ceiling and floor tiles, linoleum, caulks and sealants, mastics and roofing materials, for example.
Transmission Electron Microscopy (TEM) - detection of asbestos in NOB samples is often extremely difficult because of the small fibres used during manufacture and the organic matrix used as a coating. Polarized Light Microscopy is not a reliable method in these instances because of the magnification limitations; TEM is currently the only method that should be used to determine if this materials can be considered or treated as non-asbestos containing.
Further, in New York State, NOB samples must be analyzed by the Gravimetric Reduction Method, which combines extreme heat to burn off organic compounds and hydrochloric acid to eliminate soluble compounds.
Surfacing Material Testing
Materials that are sprayed, troweled or otherwise applied to surfaces, such as fireproofing materials on structural beams or acoustical plaster on ceilings containing vermiculite are likely to be asbestos containing materials.
While not all vermiculite is dangerous, most of it manufactured up until the early 1990s originated from the Libby, Montana mine, which was known to contain tremolite asbestos.
Vermiculite Asbestos Insulation (VAI) protocols - there is no method to distinguish Libby Mine vermiculite from non-ACM vermiculite. As such, the NYS DOH lists vermiculite as a suspect miscellaneous asbestos-containing material. The New York State DOH advises to assume that vermiculite insulation contains asbestos.
For vermiculite used in thermal insulation and surfacing materials, New York State allows for testing via PLM. If less than 10% of the entire material composition is vermiculite and no asbestos fibers are detected, the material may be reported as non-ACM. However, if any asbestos fibers are identified, an asbestos analysis must proceed and be reported/managed as ACM. Also, if 10% or more of the material is vermiculite, it must be reported as ACM.
For vermiculite in attic fill, block fill and other loose bulk insulation materials, NYS DOH guidance indicates a greater public health concern because these material can easily release asbestos fibers if disturbed during renovation or demolition projects. Because there is no approved analytical method to reliably confirm vermiculite as non-asbestos, NYS DOH mandates these materials be designated as ACM.
As you can see, there are a variety of approaches to testing for Asbestos. The combination of methods used will vary depending on your, or your client’s, unique situation. If you have any questions or would like to discuss, please contact us.
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