Simulation Tests to Assess Occupational Exposure to Airborne Asbestos from Asphalt-Based Roofing Products
1 Health Sciences, Exponent, Inc., 149 Commonwealth Drive, Menlo Park, CA 94025, USA
2 Health Sciences, Exponent, Inc., 500 12th Street, Suite 220 Oakland, CA 94607, USA
* Author to whom correspondence should be addressed. Tel: (650) 688-1782; fax: (650) 688-1799; e-mail: fmowat{at}exponent.com
This study sought to evaluate exposure from specific products to evaluate potential risk from roof repair activities. Five asbestos-containing fibered roof coatings and plastic cements, representing a broad range of these types of products, were tested in exposure simulations. These products were applied to representative roof substrates. Release of asbestos fibers during application and sanding of the product shortly thereafter (wet sanding) were tested initially. Other roof substrates were cured to simulate a product that had been on a rooftop for several months and then were tested to evaluate release of fibers during hand sanding and hand scraping activities. Additional tests were also conducted to evaluate asbestos release during product removal from tools and clothing. Two personal (n = 84) and background/clearance (n = 49) samples were collected during each 30-min test and analyzed for total fiber concentration [phase-contrast microscopy (PCM)] and for asbestos fiber count [transmission electron microscopy (TEM)]. PCM concentrations ranged from <0.005 to 0.032 fibers per cubic centimeter (f cc–1). Chrysotile fibers were detected in 28 of 84 personal samples collected. TEM concentrations ranged from <0.0021 to 0.056 f cc–1. Calculated 8-h time-weighted averages (TWAs) ranged from 0.0003 to 0.002 f cc–1 and were comparable to the background TWA concentration of 0.0002 f cc–1 measured in this study. Based on these results, it is unlikely that roofers were exposed to airborne asbestos concentrations above the current or historical occupational guidelines during scraping and sanding of these products during roof repair.
Keywords: asbestos • curing • exposure simulation • occupational exposure • plastic cement • roof coating
Received January 4, 2007; in final form March 26, 2007
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