Healthy Indoors Magazine - USA Edition

COVER STORY—March/April 2017 12 the containments are very clean or that asbestos is not becoming airborne during the sampling event. Given the outcome of the projects mentioned pre- viously where settled dust samples were collect- ed, I tend to believe that there may be a hidden contamination problem the industry is missing. The methods used to determine if the asbestos has been removed may not be thorough enough. The unaided eye cannot see microscopic particles. Air sampling devices cannot collect asbestos parti- cles if the particles are not entrained in the air. So to improve the effectiveness of an abatement project, why not collect settled dust samples to make sure that the entire containment is clean and that the re- sponse action is truly complete? All asbestos con- taining materials removed + no asbestos in settled dust + no asbestos in the air = clean containment. Let's look at a similar scenario with a different contaminant—lead. Lead clearance as mandated by the Environmental Protection Agency has re- quired sampling of settled dust. Why? Because lead is heavy, settles out of the air quickly, and the hazard is ingestion of lead-containing dust. No air sampling is mandated for lead clearance. Yes, I know, most asbestos fibers are much lighter than lead particles, but some will still settle. The small fibers will be entrained in the air and drawn into the HEPA filters; the larger particles will settle out. Now the fun begins—sampling settled dust. There just happens to be a method for determining asbestos contamination on surfaces. The folks over at ASTM developed the method about twenty years ago. The specific reference is ASTM D5755 Stan- dard Test Method for Microvacuum Sampling and Indirect Analysis of Dust by Transmission Electron Microscopy for Asbestos Structure Number Con- centrations. A summary of the method follows. For a copy of the complete method, contact ASTM. Collecting dust samples is straightforward. Materials needed: • 25 millimeter or 37 millimeter sampling cas- settes containing a mixed cellulose ester (MCE) filter with pore size less than or equal to 8 microns (standard PCM or TEM sam- pling cassettes work great), lying around, there are bound to be asbestos fibers in the dust. Make sure the abatement contractor cleans these areas thoroughly (HEPA vacuumed and wet wiped, not just picking up the bulk pieces) otherwise asbestos may still be hiding in the dust. Is air sampling adequate to define cleanliness? The protocol established by the Environmental Protection Agency is usually the preferred meth- od for clearance sampling. This method requires aggressive agitation of the air inside containment. This is usually accomplished with a leaf blower and box fans. Samples are then collected in and around the containment. The problem arises when all the surfaces inside the containment are not blown with the leaf blower. In some containment areas, blowing every surface may take hours to accomplish. As a TEM laboratory, QuanTEM re- ceives thousands of these clearance air samples from abatement activities each year and the vast majority (>90%) contain no detectable amounts of asbestos. This either means that the majority of

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