Asbestos NESHAP Requirement to Perform Point Counting on Friable Asbestos-Containing Material (ACM)

INTRODUCTION

The U.S. Environmental Protection Agency (EPA), National Emissions Standard for Asbestos (NESHAP) Standard, 40 CFR 61, Subpart M, regulates the disposal, manufacturing, fabricating, demolition, renovation, and spraying of asbestos-containing material, (ACM), which have an asbestos concentration of greater than one percent, by area. In addition, the above referenced rule requires friable ACM be point counted, by polarized light microscopy (PLM), to quantify asbestos in materials estimated to contain less than ten percent asbestos.

CLARIFICATION OF THE RULE

EPA has issued a memorandum, dated May 8, 1991, clarifying the point counting requirement. This memorandum applies to all regulated asbestos containing material (RACM), which is defined in 40 CFR Part 61, Section 141. The memorandum recommends the following procedures be followed for the analysis of RACM:

If after analyzing a sample by polarized light microscopy, no asbestos is detected, point counting does not have to be performed. A minimum of three prepared slides should be analyzed and found to be negative for asbestos before making this determination.

If the analyst visually estimates the amount of asbestos in a sample of potential RACM to be less than ten percent, the building owner, or operator, may choose to either, (1) assume that the material contains greater than one percent and treat the material as RACM, or (2) have the amount verified/ quantified by point counting. The final result that is obtained from point counting is the result that is to be reported.

If the amount of asbestos is observed in the sample, using PLM, but no fibers were counted during the point counting procedure, the results should be reported as "trace" asbestos. (This occurs when asbestos is seen on the slide, but no fibers fall under the graticule while point counting.)

REVISED METHOD FOR BULK ANALYSIS

EPA published a "Notice of Advisory" in the Federal Register on August 1, 1994, to "announce the availability of an improved bulk sample analysis test method". This procedure, "Method for the Determination of Asbestos in Bulk Building Materials" (EPA/600/R-93/116) was developed to enhance analysis of floor tiles and other non-friable material, improve precision, especially at lower concentrations, and "clearer instruction on the analysis of bulk materials, particularly where multiple layers are present". This method includes a provision for using calibrated visual estimation, using a set of standards containing known concentrations of asbestos, to calibrate the analyst, or for using point counting to quantify lower percentages of asbestos in samples. The calibrated visual estimation method trains the analyst to visually estimate percentages more accurately. EPA recommends using this method in place of the 1982 EPA "Interim Method for the Determination of Asbestos in Bulk Insulation Samples". This newer method is appropriate, except when reporting asbestos concentrations (<10%) of potential RACM, where point counting must be utilized, as is explained in EPA's May 8, 1991, point counting memorandum,

WHAT HAVE STUDIES SHOWN?

An experienced analyst can detect asbestos in samples containing less than one percent if the asbestos fibers are of sufficient size to be resolved by the polarized light microscope. However, quantifying low concentrations is difficult. According to Robert Perkins, with Research Triangle Institute, results from point counting studies concluded the following:

Visual estimates of asbestos concentrations tend to be higher than concentrations determined by point counting;

Proper homogenization of samples, and proper slide preparation are necessary to achieve representative results from point counting; and

Point counting is time consuming, and, therefore, more expensive, but the results are more accurate and precise than visual estimation.

WHAT DO REGULATIONS REQUIRE?

Bulk Friable material, containing less than one percent asbestos, by area, and as determined by point counting, is not regulated under the Asbestos NESHAP rule. The Department of U.S. Department of Labor, Occupational Safety and Health Administration (OSHA) regulates employee exposure to material containing greater than 1% as determined by procedures in 40 CFR Part 763, Appendix E, Subpart E. Clarification of OSHA's requirements must be obtained from the local office of OSHA.

CONCLUSION

The benefit of point counting is that it produces a systematic means of quantitative analysis. Point counting is dependent on the analyst's ability to correctly identify asbestos in a sample. Thorough examination of the entire sample (using a stereo microscope), obtaining a homogenous sample, and careful slide preparation will improve the analyst's ability to detect and quantify asbestos, either by visual estimation, or by point counting. The use of calibrated asbestos standards should improve an analyst's ability to visually estimate low percentages of asbestos, and, therefore, assist the analyst in concluding the need to perform point counting.

REFERENCES

Perkins RL. 1989. Point-Counting Technique for Friable Asbestos Containing Materials, Research Triangle Institute. Microscope, 1990, pp. 29-39.

Webber JE, Janulis RJ, Carhart LJ,,Gillespie MB. 1990. Quantitating Asbestos Content in Friable Bulk Samples: Development of a Stratified Point-Counting Method. American Industrial Hygiene Association J.51(8): 447-452.

U.S. Environmental Protection Agency.1992.40 CFR 61 Subpart M. National Emissions Standard for Asbestos. Washington,DC: U.S. Environmental Protection Agency.

U.S. Environmental Protection Agency. 1992. 40 CFR Part 763 Section 1. Washington,DC: U.S. Environmental Protection Agency.

U.S. Department of Labor. 29 CFR Part 1926 Section 58. Occupational Health and Environmental Controls. Washington, DC: U.S. Department of Labor.