How to Detect Asbestos?
Various testing methods have been developed to test for the presence of asbestos, and which test method to use largely depends on the type of matrix being analyzed.
Phase Contrast Microscopy (PCM) is widely used to measure fiber concentrations of air samples. This is routinely done at asbestos abatement sites and can be applied for environmental monitoring, personnel monitoring, and clearance testing for minor abatement projects.
The PCM technique has the advantage of fast turnaround time and low cost. This light microscope technique operates at magnifications of 400X and will resolve fibers larger than 0.25 microns (um) in diameter.
PCM is not utilized to distinguish asbestos fibers from other fibers (ex: gypsum, mineral wool, fiberglass, cellulose etc.), but rather to give a overall reading of various types of fibers present in the sample.
Consequently, an analysis by PCM indicating high fiber counts does not necessarily indicate the presence of asbestos. Likewise, low fiber counts by PCM can not conclude 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..
The current revision of the National Institute of Occupational Safety and Health (NIOSH) Method 7400 is employed for PCM analysis. Proficiency Test is provided for the laboratory through the American Industrial Hygiene Association (AIHA) PAT programs, and Seattle Asbestos Test conducts extensive Quality Assurance and Quality Control (QA/QC) regimens are performed as part of our ongoing certification program.
Transmission Electron Microscopy (TEM) represents the most sophisticated technology available for characterizing asbestos minerals. This technique is now the standard for most airborne investigations including post abatement clearance testing as well as diagnostic and environmental monitoring activities.
Using magnifications routinely at 20,000X or greater and employing powerful chemical (EDXA) and mineralogical (SAEDP) tools, the TEM can differentiate, not only asbestos from non-asbestos fibers, but also can classify the several species that comprise asbestos minerals. The sample preparation and analysis process precludes turnaround time that would be available for PCM. The typical soonest TEM RUSH analysis on a set of AHERA samples can be conducted in four to six hours.
Bulk Building Materials
The analysis of Bulk Building Materials for asbestos content is primarily conducted by PLM, and to a lesser degree by XRD, SEM and TEM.
As stated above, Polarized Light Microscopy (PLM) is the technique most often employed for the analysis of bulk building materials. The light microscopy technique utilizes the unique features of polarized light to observe mineral specific optical properties. In this manner, PLM can differentiate asbestos from non-asbestos fibers and further classify the various species that compose the asbestos mineral family. Moreover, the technique records the identity of the non-asbestos fibrous component of each bulk building material sample.
The PLM procedure provides an economical technique for screening large numbers of samples. However, as with PCM, there are limitations to light microscopy testing due to the magnification (100-400X) employed and due to other interferences present in the building material matrix (ex: tar and petroleum binding components, sub-micron particulate adhering to the surface of asbestos mineral, etc.).
PLM results are reported as a percentage of the total sample. PLM utilizes a few protocols for the quantification process. These include visual estimation and point counting. (See FAQ) Depending on the sample matrix, PLM analytical sensitivity can be a fraction of a percent. Gravimetric reduction protocols (ELAP 198.1, EPA 600) further enhance this technique's ability to accurately quantify and qualify asbestos.
The current method employed for these analyses is found in EPA 600/R-93/116. Other procedures are also utilized to supplement this method such as NIOSH 9002, and OSHA ID 191. Accreditation is primarily provided by the National Institute of Standards and Technology (NIST) through the National Voluntary Laboratory Accreditation Program (NVLAP).
Seattle Asbestos Test is a NVLAP accredited laboratory and conducts extensive Quality Assurance and Quality Control (QA/QC) regimens are performed as part of an ongoing program. It participates in proficiency testing is primarily conducted through the Proficiency Analytical Testing Program (PAT) administered by NVLAP and receives on-site technical evaluations are also primarily conducted through NVLAP.
The gravimetric reduction process usually employed on Non-Friable Organically Bound (NOB) building materials (ex: floor tiles, roofing materials, etc.) is particularly well suited for TEM confirmation of negative PLM samples.
Settled Dust and Other Non-Building Materials
The analysis of Settled Dust and other Non-Building Materials for asbestos content continues to be a growing and controversial subject in the environmental industry. Whether to establish baseline levels, survey historical buildup, or to diagnose episodic releases, the utility of surface dust analysis has proven efficacy for the environmental professional.
The established methods published by ASTM call for detailed field sampling schemes and analysis by TEM. ASTM D5575, D5576, and D6480 have been developed for this specialized analysis. Though TEM is the method of choice, proprietary in-house methods using PLM can be employed. IATL cautions its clients against the use of non-peer reviewed methods due to the limitations of certain analytical techniques.
Data interpretation may prove difficult for these methods. There are several comprehensive references available for responsible environmental professionals who desire to be informed of the utility of these methods.
Soil and Sediment
The analysis of Soil and Sediment for asbestos content continues to be a valuable tool for environmental investigations (e.g. possible illegal dumping of asbestos building materials). In all, the sampling and analysis procedures developed by EPA Region I and others have proven efficacy and utility for the environmental professional.
The established methods published by EPA call for detailed field sampling schemes and analysis by PLM. Though PLM is the method of choice due to its economy, proprietary in-house methods using TEM can be employed. IATL cautions its clients against the use of non-peer reviewed methods due to the limitations of certain analytical techniques. Data interpretation may prove difficult for these methods. There are several comprehensive references available for responsible environmental professionals who desire to be informed of the utility of these methods.
Water and Other Aqueous Samples
The analysis of Water and Other Aqueous samples for asbestos content continues to mature. This growth is evidenced by recent method developments by EPA. Investigations of asbestos in drinking water are conducted when water supply pipes are disturbed or replaced. Municipal utilities serving certain populations are required to test this analyte. Often effluent or waste streams are tested to survey industrial contamination.
The established methods are published by EPA 100.1 and 100.2, and these methods call for detailed field sampling schemes and analysis by TEM.