Future Environment Designs Training Center's Blog: Electron Microscopy

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Tuesday, July 11, 2017

Asbestos Floor Tile Debate Results

… … … This debate regarding asbestos floor tiles started at the Professional Abatement Contractors of New York's (PACNY's) 2017 Environmental Conference. At the conference, after our presentation, a member of the audience challenged our statement that asbestos floor tile removal should be cleared by the Asbestos Hazard Emergency Response Act (AHERA) Transmission Electron Microscope (TEM) method (see the video of our presentation here, the challenge is at the end of the video). In the video Mr. Chris Alonge, of Dormitory Authority of the State of New York (DASNY) defends our call for TEM clearance for asbestos floor tiles and we had some additional people approach us after the presentation supporting our side of the debate. As some of you know, we decided it would be neat to see if their are others who feel the same way. We decided to use Survey Monkey to ask three simple questions regarding this issue. These questions were:

When doing asbestos flooring removal, which method was used the National Institute of Occupational Safety and Health (NIOSH) 7400 Phase Contrast Microscope (PCM) method or AHERA TEM method for clearance? The answers we got was 47.1% used the NIOSH 7400 method; while 29.4% used both methods; and 23.5% only used the TEM method.

When using the AHERA method for clearance, what was the typical size of the fibers found? The answers we got were 58.8% less than 5 micron; 29.4% both sizes were equal amounts; and 11.8% greater than 5 micron.

Have you ever encountered during asbestos flooring removal when utilizing both the NIOSH 7400 (PCM) & the AHERA (TEM) methods of analyses, that the NIOSH 7400 passed while the AHERA method failed? The answers we got were 52.6% yes, 36.8% no, and 10.5 never used both.

Improperly Removed Floor Tiles

We would like to thank all of you who participated in our survey. The results are interesting, the first question is not surprising since the NIOSH 7400 method is the cheapest method and both New York State (NYS) and New York City (NYC) require this method as the minimum method. The second question is also not surprising since this is the reason for our call for clearance for floor tile jobs to be by the AHERA TEM method. The final question proves the point we've been making. If even one project can actually fail by AHERA TEM but pass using the NIOSH 7400, this should be a concern for any person who is concerned for the safety and health of the occupants who would occupy the space after clearance.

Another Improper Floor Tile Removal

As we mentioned in our presentation, we didn't come up with this idea out of the blue. In 2003, Applied Occupational and Environmental Hygiene published a study called "Asbestos Release During Removal of Resilient Floor Covering Materials by Recommended Work Practices of the Resilient Floor Covering Institute" by Marion Glenn Williams, Jr. and Robert N. Crossman, Jr. from the University of Texas Health Center at Tyler, Tyler Texas. You can find the study in our Future Environment Designs website under our Resource Page in the dropbox folder.

Some of the major points from this study were:

Asbestos used in flooring materials is Grade 7 - Shorts and Floats. The dimensions of this material are very small and may not be resolvable by the Polarized Light Microscope (PLM). Which is why in NYS we require floor tiles to be analyzed as a nonfriable organically bound (NOB) material (analysis by PLM and if negative result for asbestos then analysis by TEM).

Since the dimensions of these fibers used in the manufacture of floor tiles are so small, it would explain why we typically see very low personal exposure levels by phase contrast microscope (PCM) during floor tile removals. Many ultrafine fibers are not counted due to resolution (0.2-0.25 um) and the count protocol, which provides that only fibers longer than 5 micron with a 3:1 or greater length-to-width ratio are counted.

Many research studies have found the preponderance of fibers at autopsy left in lung tissue, pleural plaques, and lymph nodes of persons who have occupational exposure to asbestos are shorter them 5 micron in length.

The NIOSH 7402 TEM method is flawed because it underreports the amount of asbestos in the samples because it ignores all fibers less than or equal to 5 micron and all those fibers longer than 5 micron but less than 0.25 micron in diameter.

AHERA TEM method counts for total asbestos structures per cubic centimeter averaged 22 times greater than the PCM fiber counts on the same filters.

AHERA TEM asbestos concentrations obtained during mastic removal with a commercial mastic remover averaged 11 times higher than those measured when removal used amended water.

The study also found that there was considerable amounts of asbestos dust settled on exposed surfaces during tile removal. Indicating a need to thoroughly HEPA vacuum and wet clean surfaces or dust may remain that could be re-entrained by occupant activity.

The study also indicates that workers in these areas, would not have to wear respirators, so anyone in these areas would have inhaled asbestos fibers or structures of respirable dimensions.

The study suggests that for Resilient Flooring Removal clearance sampling should use aggressive methods, require a clearance level of less than 0.005 structures per cubic centimeter for each sample, and all samples analyzed by AHERA TEM protocol. It also suggests a minimum number of samples for clearance should be one sample per 500 square feet, a volume of air of at least 1250 liters, and the use of 0.45 micron mixed cellulose ester filters in a 25 millimeter diameter conducting cassette with a 50 millimeter extension cowl.

As we said, we did not arrive at our decision lightly. After reading this study it became apparent to us that asbestos containing flooring or mastic removal should be cleared using the AHERA TEM method to ensure the work area is actually free of asbestos fibers (we already do this in schools under AHERA for large asbestos projects, some schools require all asbestos projects ave to be cleared by AHERA TEM). In addition, any negative exposure assessment for floor tile removal that does not include AHERA TEM analysis of some of the samples should not be accepted as definitive to allow workers to not use respirators during asbestos flooring removal. As the study showed their could be significant exposure to workers from these respirable fibers/structures that the NIOSH 7400 method is not picking up.

We hope this information explains our position, and we look forward to a continuation of this debate. We intend to press the case for a requirement for AHERA TEM clearance for flooring removal, especially if New York State truly intends to move forward with an update of Industrial Code Rule 56.