Airborne Fiber Exposure Assessment of Dry Asbestos-Containing Gaskets and Packings Found in Intact Industrial and Maritime Fittings

Abstract

This study assessed airborne fiber exposures from intact asbestos-containing gaskets and packings while activities representative of historical work practices were performed. The study design eliminated analytical interferences while systematically capturing information related to activity variables. A series of gasket and packing activities was conducted according to traditional methods while sampling was performed to determine the 8-hour time-weighted average (TWA). The fittings used during this study were obtained intact from a decommissioned industrial power plant and U.S. Navy destroyers. The activities tested included flat blade scraping, hand wire brushing, power wire brushing, making gaskets with a ball-peen hammer, and stem packing removal and replacement. All activities were performed dry. Results for every area and personal sample showed the 8-hour TWAs were well below the current Occupational Safety and Health Administration permissible exposure limit of 0.1 f/cc. A database of more than 400 points was developed to analyze information from variable factors related to the tests. These factors included, for example, type of gasket, composition of the gasket, percentage of gasket adhering to a flange surface, gasket surface area, and minutes elapsed for removal. The results demonstrate a very low rate of fiber exposure from routine activities associated with asbestos-containing elastomeric gaskets and impregnated packing.

Airborne asbestos exposures associated with gasket and packing replacement: A simulation study of flange and valve repair work and an assessment of exposure variables

“…In this study, the percentage of gasket material adhered to the flange surface and gasket surface area, among many other variables, showed no significant correlation to the air sample results (Boelter et al, 2002). Further quantitative investigation of the effects of gasket surface adherence on airborne asbestos exposures would be useful for evaluating exposure potential in situations where gasket adherence is likely to influence how and the extent to which gaskets are removed from the flange surface.…”

“…To our knowledge, Boelter et al (2002) is the only study to date to quantitatively investigate the influence of gasket surface adherence on asbestos exposures. In this study, the percentage of gasket material adhered to the flange surface and gasket surface area, among many other variables, showed no significant correlation to the air sample results (Boelter et al, 2002).…”

“…Many of the aforementioned studies examined exposures resulting from gasket work on a variety of equipment types. Boelter et al (2002) collected data on different types of flange surfaces and gaskets, but none of these studies have examined whether there are differences in asbestos exposure based on the location of the gasket or type of flange surface.…”

“…First, the majority of the existing exposure studies have investigated exposures associated with a single product, task, or tool and few have measured exposures resulting from a combination of individual tasks that would comprise a complete equipment overhaul (e.g., single/multiple gasket or packing replacement; equipment overhaul/replacement). Of the available worksite and simulation studies, five have examined exposures resulting from replacement of gaskets and/or packing materials over the course of an 8-h working day (Boelter et al, 2002(Boelter et al, , 2011Mangold et al, 2006;Spencer, 1998b;Cheng & McDermott, 1991). Although helpful to characterize exposures of a particular activity (e.g., gasket removal or gasket fabrication) that may be repeated several times within a workday, these data are not collected during the time over which only the task was performed (i.e., workday vs. task-based sampling), thus making it difficult to extrapolate these data to scenarios in which a combination of multiple tasks (e.g., gasket removal and fabrication) are performed at varying frequencies over the workday.…”

“…To characterize exposures solely from work involving gaskets and packing material, a number of simulation studies have been conducted examining asbestos exposures associated with this type of work (McKinnery & Moore, 1992;Spencer, 1998a,b;Fowler, 2000;Longo et al, 2002;Boelter et al, 2002Boelter et al, , 2011Millette & Mount, 1993;Mangold et al, 2006;Madl et al 2014). If conducted properly, simulation studies remove the confounding variables of worksite studies and can more precisely represent exposures associated with a particular task and/or product.…”