Paper No. 7
Presentation Time: 3:35 PM
FUNDAMENTAL FLAWS OF AHERA TEST METHOD FOR DETERMINING ASBESTOS CONCENTRATION OF BULK INSULATION SAMPLES
SU, Shu-Chun, Washington, DC 20007, shuchunsu@gmail.com
The Asbestos Hazard Emergency Response Act (AHERA) was signed into law in 1986. It mandates the use of U.S. Environmental Protection Agency (EPA) Interim Method for the Determination of Asbestos in Bulk Insulation Samples (EPA 600/M4-82-020) to determine whether a bulk insulation sample is asbestos-containing material (ACM, the weight percentage of asbestos fibers is >1%) or not (Non-ACM, the weight percentage of asbestos fibers is £1%) by polarized light microscopy. By analyzing results of Proficiency Testing conducted by NVLAP (National Voluntary Laboratory Accreditation Program) from 1989 to 2011, it can be concluded that the practices of hundreds of American environmental laboratories in using EPA 600/M4-82-020 test method have proven that it lacks the necessary accuracy and precision to differentiate ACM from Non-ACM. Over the past 33 years, false positive and especially false negative results were considered to be acceptable in this most stringent test of capabilities of environmental laboratories. The fundamental flaws of EPA 600/M4-82-020 test method can be summarized as follows:
- it has ignored the issue of the significant differences between weight percentage (wt%) and area percentage (area%) for fibrous asbestos components distributing loosely in mostly granular matrix particles with densities significant lower than those of regulated asbestos minerals;
- it has ignored the issue of the minimum amount of sample to be analyzed to reach the required analytical sensitivity of 1 wt%;
- it has ignored the issue of the required margin of error and confidence level in differentiating ACM from Non-ACM samples;
- it has ignored the issue of sample size by adopting a “one-size fits all” rule that mandates counting 400 non-empty points in point counting procedure regardless of margin of error and confidence level.
This talk analyzes critical issues related to the determination of asbestos concentrations in bulk samples and proposes detailed solutions to address the above flaws.
