| Abstrakt: |
Asbestos abatement workers may be exposed to asbestos despite wearing high performance respirators. The respirator protection factors tested in the laboratory may differ from those in real work situations. Also, poorly operating high efficiency particulate air (HEPA) filtration units and deficient enclosures may contaminate the surroundings of the asbestos abatement site. To study the workers' real exposure, we developed a method for sampling the inhalable air inside the respirator via an injection needle through a conductive cowl on a sampling filter. We studied the performance of full-face mask respirators withP3 filters and HEPA air filtration units at 21 work sites. The sample filters were analyzed by phase contrast microscopy and scanning electron microscopy. Only 8 of the 21 tested respirators (38%) hilly protected the workers against fibers [<0.01 fibers/cc (f/cc)]. In the other 13 respirators, the fiber levels varied from 0.01 to 4.6 f/cc, with a mean concentration of 0.46 f/cc and a median concentration of 0.12 f/cc. The 8-hour time-weighted average exposures were usually low (< 0.01 to 0.15 f/cc), but in four cases (0.15, 0.2, 0.49, and 2.0 f/cc) the 8-hour concentration exceeded the Occupational Safety and Health Administration permissible exposure level for asbestos (0.1 f/cc). The respiratory protection factors varied from 5 to 18,000. Fiber leakage through the face seal may occur in difficult working postures,or through poorly fitted filter systems (e.g., in multisupplier systems). In 8 of the 21 work sites, malfunctioning of the HEPA units andthe enclosures (filtering efficiencies 41.6 to 99.49%) could be detected. Asbestos concentrations inside the respirator can be measured by the developed method. Better quality management for the asbestos abatement firms is recommended. More effective maintenance and fit-testing of the respirators and less dusty abatement methods must be emphasized in the training of the workers. HEPA units and respirators needreg [ABSTRACT FROM AUTHOR] |
