Healthy Indoors Magazine
Issue link: https://hi.healthyindoors.com/i/866924
Healthy Indoors 13 bestos Sampling Bulletin (September 30, 1994). EPA, Washington, DC.) stating that in the event flooring materials are reported at 1 percent or less by PLM analysis, the asbestos content should be determined by TEM bulk analysis methods. In addition, the National Voluntary Laboratory Accreditation Program (NVLAP) accreditation program re- quires accredited laboratories to insert a dis- claimer in the laboratory report stating that "PLM is not a valid method for determining asbestos content in floor covering materials and if the analysis is reported at 1 percent or less, analytical transmission electron micros- copy (ATEM) bulk methods should be used." The EPA has published (EPA/600/R-93/116) a TEM analysis method for floor tiles and other small fiber–containing materials. • 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 proto- col, which provides that only fibers longer than a survey to ask three simple questions regarding this issue. These questions were: • When doing asbestos flooring removal, which method was used: the National Institute of Oc- cupational Safety and Health (NIOSH) 7400 Phase Contrast Microscope (PCM) method or AHERA TEM method for clearance? The results were 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 clear- ance, what was the typical size of the fibers found? 58.8% answered less than 5 microns, 29.4% said both sizes were equal amounts; and 11.8% reported greater than 5 microns. • 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? 52.6% stated yes, 36.8% no, and 10.5 never used both. The survey results are interesting. The top re- sponse to the first question is not surprising since the NIOSH 7400 method is the cheapest meth- od and is typically the minimum method used for clearance. The second question results are also not surprising since this is the basis of our call for clearance on floor tile jobs to be by the AHERA TEM method. The answers we received on our final question supports the point we have been trying to make. If even one project can fail by AHERA TEM, but pass using the NIOSH 7400, this trigger concerns for the safety and health of the occupants in that the space. This isn't a new concern. In 2003, Applied Oc- cupational and Environmental Hygiene published a study called "Asbestos Release During Remov- al of Resilient Floor Covering Materials by Rec- ommended 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, Tyler, Texas. 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 re- solvable by the Polarized Light Microscope (PLM). This is why the Environmental Pro- tection Agency (EPA) has a policy guidance (U.S. Environmental Protection Agency: As- Another Improper Floor Tile Removal