Evaluation of airborne chrysotile concentrations associated with packing replacement during valve repair or overhaul

Asbestos was used in certain packing products for much of the twentieth century. The objective of this study was to characterize exposure from working with and around chrysotile-containing packing during valve repair and overhaul to better understand the exposure potential of career pipefitters and other tradesmen, as well as bystanders and household contacts. Airborne fiber and chrysotile concentrations during packing (20.91-62.77% chrysotile) replacement were measured during standard and nonstandard work tasks involving valve repair and overhaul, cleanup, and clothes handling. Packing replacement was performed on 21 valves by a career engineer at a facility with no mechanical ventilation. Out of 126 air samples, 56 had airborne fiber concentrations above the limit of detection using phase contrast microscopy (PCM) analysis and were subsequently analyzed by transmission electron microscopy (TEM); chrysotile was detected in 21 of the 56 samples. Packing replacement in 16 valves in succession without additional manipulation (such as sanding or compressed air blowout) resulted in a task-based personal average concentration of 0.0378 f/cc, PCM-equivalent asbestos-specific fibers or PCME, while one valve replacement event with compressed air use resulted in an average concentration of 0 f/cc, PCME, and compressed air and sanding combined resulted in an average concentration of 0.0018 f/cc, PCME. Task-based personal sampling during cleanup resulted in concentrations averaging 0.0047 to 0.0162 f/cc, PCME; no chrysotile was detected in task-based close bystander area samples, nor in any samples collected during clothes handling and post-handling cleanup. Regression analysis showed no correlation between PCM concentrations and measured size-fractionated and total airborne particulate matter concentrations. The results indicated that for packing replacement, including work on 16 valves in succession, lack of mechanical ventilation, and nonstandard work practices, all partial-shift and task-based average personal and area airborne fiber concentrations were below the OSHA 8-hr Time-Weighted Average (TWA) Permissible Exposure Limit (PEL) of 0.1 f/cc and 30-min TWA Excursion Limit (EL) for asbestos of 1 f/cc, consistent with previous literature.