Asbestos Testing in Air

Asbestos, once extolled as the miracle mineral, has been a focus of national debate for many years due to delayed and uncertain responses by government and resistance by corporate entities to protect people from its known toxicity. Asbestos represents an important case study in public health; government, medical professionals, and industry managers first recognized the harmful properties of asbestos almost a century ago, and yet decades passed before regulatory agencies began acting on this information.

Asbestos applications result from its many unique physical attributes. Its high tensile strength stabilizes mixtures with concrete, asphalt, and plastic. Asbestos also offers a stable material for frictional use, such as brake surfaces. Because of the length and pliability of its fibers, it has been incorporated into specially manufactured products, including gaskets, pads, fabric sheets, and asbestos paper with intrinsic properties of resistance and strength. Since it is fireproof and block heat transfer, it represents an ideal insulation material. It has been applied in economical fashion to building surfaces for fire protection and heat retention. It has been used to encase furnaces and kilns in both its fabric and compacted-brick forms.

Very limited information is available on the number of workers still exposed to asbestos in the USA. Overall, exposure patterns have changed from historically chronic exposures (manufacturing processes, cement pipe fabrication) to short-term, intermittent exposure occurring through maintenance and remediation work. Although asbestos is no longer mined in the USA, NIOSH estimates that 44,000 miners and other mine workers may be exposed to asbestos or amphibole cleavage fragments during the mining of some mineral commodities. Recently, OSHA has estimated that 1.3 million employees in construction and general industry face significant asbestos exposure on the job.

Exposure to asbestos in the ambient indoor and outdoor environments comes from many sources, both natural and man-made. Chrysotile asbestos, which accounts for over 90–95 % of the asbestos used in the United States, has become a ubiquitous contaminant of ambient air. It has been noted that asbestos fiber can be found in the lungs of almost everyone in the American population. Natural sources of asbestos fiber release include weathering and erosion of asbestos-containing rock and of road surfaces composed of asbestos ores. If the primary areas of source rock are compared with high population density, the most critical areas for emissions from natural sources appear to be eastern Pennsylvania, southeastern New York, southwestern Connecticut, and greater Los Angeles and San Francisco.

Fig.1 Workers in the North Carolina asbestos-abatement program (Darcey D.J. et al. 2014)

Different techniques have been developed for measuring the concentration of asbestos in ambient air and in the workplace. The phase-contrast light microscope for counting fibers in the workplace has been less useful in the ambient environment, where fiber identity and character are usually unknown, fibers are too small to be seen by light microscopy, and concentrations expressed as mass are usually hundreds or thousands of times lower than those in the workplace.

Fiber concentrations in the workplace have generally been measured as the number of fibers longer than 5 μm and an aspect ratio of 3:1 or greater. Ambient concentrations are now determined by transmission electron microscopy and usually are expressed as mass per unit volume (nanogram per cubic meter). Because of intrinsic variability in the unit weight of individual fibers, the conversion factors relating mass concentration to optical fiber concentration range widely from 5 to 150 μg/m³/f/cm³.

Measurements via transmission electron microscopy have established background concentrations of asbestos in urban ambient air at generally less than 1 ng/m³ (0.00003 fibers/cm³) and rarely more than 10 ng/m³ (0.00033 fibers/cm³). Figure 2 summarizes fiber concentration data from a variety of studies in both urban and rural areas.

Fig.2 Summary of asbestos exposure samples in different environments (Campbell R. et al. 2009)

By incorporating leading-edge analytical instruments and advanced analyst methods, we can offer excellent asbestos testing services in air. As an outcome of these high-end lab necessities, our clients enjoy a streamlined experience, short waiting times, and easy-to-read reports and certifications.

References

• Darcey D.J., Feltner C. (2014) Occupational and Environmental Exposure to Asbestos. In: Oury T., Sporn T., Roggli V. (eds) Pathology of Asbestos-Associated Diseases. Springer, Berlin, Heidelberg.

• Campbell R., Webber J.S., Sato H. (2009) Asbestos in the United States. In: Sato H. (eds) Management of Health Risks from Environment and Food. Alliance for Global Sustainability Bookseries (Science and Technology: Tools for Sustainable Development), vol 16. Springer, Dordrecht.