Evaluation of employee exposures to Libby amphibole asbestos during forest management activities in the Kootenai National Forest
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Evaluation of employee exposures to Libby amphibole asbestos during forest management activities in the Kootenai National Forest

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  • English

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    • Journal Article:
      NIOSH health hazard evaluation report
    • Description:
      The Health Hazard Evaluation Program received a request from managers serving the Kootenai National Forest in Montana. The request concerned employees' potential exposure to Libby amphibole during forest management and fire suppression activities in an area surrounding a former vermiculite mine. The site has approximately 40 full-time employees, and up to 100 additional employees in the summer. Work shifts are typically 8-10 hours per day. Most of the work involves land management activities, including civil engineering, trail and road maintenance, forest biology, fuels and timber management, hydrology, and wildland fire suppression. Our evaluation included (1) observing work activities and use of PPE, and (2) collecting and analyzing the samples for asbestos and Libby amphibole. We collected full shift and activity-based personal air samples on employees conducting various forest management activities; bulk samples of bark, duff, and soil; and wipe and vacuum samples from surfaces in the hydrology lab. Six of 109 personal air samples analyzed by PCM exceeded the occupational exposure limit of 0.1 f/cc; however, we found non-asbestos material that met the definition of a fiber on these samples. Of the 27 personal air samples evaluated by TEM, which included the six air samples exceeding 0.1 f/cc, six contained mineral fibers. Five of six contained richterite (one of the fibers that compose Libby amphibole), and one contained chrysotile (a serpentine form of asbestos). Of the five samples containing richterite, four were collected during fireline construction and one was collected during tree thinning. On the basis of these results, we found that employee exposures to Libby amphibole did not exceed occupational exposure limits during activities in the mine area. We detected no Libby amphibole in the bulk or surface samples. Employees wore respirators during trail maintenance and fuel reduction activities and completed a 3-stage decontamination; removed and discarded equipment and clothing, showered, and changed into street clothing. We recommended the employer (1) create a respirator program for employees working in the mine area, (2) periodically monitor employees' exposure to Libby amphibole, (3) analyze samples for Libby amphibole by electron microscopy in addition to current methods, (4) schedule dust generating work when the potential for dust generation is low, and (5) train employees on good work practices to minimize dust.

      Recommended citation for this report: NIOSH [2014]. Health hazard evaluation report: evaluation of employee exposures to Libby amphibole asbestos during forest management activities in the Kootenai National Forest. By Butler C, McCleery R, Kiefer M, Harper M, Lee E, Wallingford K. Cincinnati, OH: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, NIOSH HHE Report No. 2012-0077-3223.

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