This article is a quick guide to the types of asbestos, where they were used, and where they may turn up in case of legacy demolitions or reconstructions. The reader will note that the EPA uses the term “Commercial Asbestos” to differentiate from NOA or Naturally Occurring Asbestos. Commercial asbestos means any material containing asbestos that is extracted from ore and has value because of its asbestos content. On the other hand, NOA is a more modern term that indicates it is a material in which asbestos was not added during manufacturing, but is there in small amounts naturally. It is very uncommon for NOA materials to be regulated by EPA as asbestos-containing material (ACM) due to the asbestos content being less than one percent.
The asbestos types listed below must be identified by one of two different laboratory methods pursuant to EPA and OSHA regulations: PLM or Polarized Light Microscopy uses a light microscope at 100X magnification to identify asbestos fibers through a method called dispersion staining. This method cannot detect very fine fibers, sometimes used in putty, paint, caulk, coatings, glues, and floor tiles. Therefore, some states require that another method be used for these “Non-friable Organically Bound” NOB materials; this method is Transmission Electron Microscopy (TEM), which magnifies a sample hundreds of times more than a PLM, thereby finding the very small fibers unseen by the cheaper method. Illinois does not require NOB materials to be confirmed by TEM, but many other states do, and EPA recommends all samples that are NOB and are negative by PLM be confirmed by TEM.
These terms are important in 2022 because it seems that as more “Legacy Asbestos” is removed, we are looking harder for any Regulated Asbestos by using better and more advanced methods.
Chrysotile asbestos is the only fiber type currently being imported, processed, or distributed in the United States, albeit in very small amounts; less than 600 tons are imported yearly for chloro-alkylai diaphragms. Chrysotile is most commonly found in drywall, plaster, and floor & ceiling tiles in residential & commercial construction. Chrysotile is also found in auto parts and insulation. According to a 2016 report, chrysotile asbestos accounts for ~90% of asbestos in the US, due to the fact that it is serpentine asbestos, or can be bent, woven into cloth, and shaped into any form. On the other hand, Amphibole asbestos, which includes the other five types of asbestos ore, is a rigid, sharp fiber that cannot be bent into different shapes or forms. This is important during the abatement of ACM by asbestos abatement contractors, because Amphibole asbestos does not absorb water, and surfactants must be used during removal.
Common places chrysotile asbestos is usually found in include:
● As a building material additive to enhance strength (for example, asbestos was added to concrete, asphalt, and vinyl materials in roof shingles, pipes, siding, wallboard, floor tiles, joint compounds, and adhesives)
● As a fireproofing material applied on steel beams and columns during construction of multistory buildings
● As thermal insulation and as a means of controlling condensation
● As an ingredient in acoustical plaster
● As a component of a mixture sprayed on ceilings and walls to produce a soft, textured appearance
Tremolite & Actinolite
The AHERA granted the EPA the ability to regulate asbestos in 1986. As of 2022, 5 of the 6 types of asbestos are currently not allowed to be used in any way in the United States. Chrysotile asbestos remains legal for use in closely regulated industrial uses that are approved by EPA after a review process in the Significant New Use Rule.
Risk evaluation is ongoing for future disposal and regulation of legacy asbestos and legacy asbestos products & appliances.
For more on what to do in the instance of asbestos exposure, read our blog here.