In July 1994, cellulose insulation (CI) was nominated to the National Toxicology Program (NTP) for a comprehensive toxicological evaluation. The evaluation consisted of two components: (1) a bulk analytical characterization of CI and (2) an exposure assessment of U.S. contractors applying the CI in residential and commercial buildings. The National Institute for Occupational Safety and Health (NIOSH) was presented with an opportunity to assist in the evaluation of CI by conducting the exposure assessment through an interagency agreement with the National Institute of Environmental Health Sciences/NTP. NIOSH conducted the CI exposure assessment, which included a medical component, with 10 contractors located across the United States. During each contractor site visit, air samples were collected for total dust, respirable dust, and for scanning electron microscopy (SEM) analysis to characterize any fibers in the dust. The CI installer and hopper operator each had two SEM air samples collected for each day of CI activities. Bulk samples of the CI were collected and analyzed for metals, boron, and sulfate content. Real-time and video exposure monitoring were also conducted to further characterize the CI dust and workers' exposures. For the 10 contractor site visits, 175 personal breathing zone (PBZ) total dust, 106 area total dust, and 90 area respirable dust air samples were collected during CI related activities. There were 26 employees with total dust eight-hour time-weighted averages (8-hour TWAs) exceeding the Occupational Safety and Health Administration (OSHA) Permissible Exposure Limit (PEL) of 15 milligrams per cubic meter (mg/m3) and 42 exceeding the American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value (TLV) of 10 mg/m3. Respirable dust air sampling and real–time monitoring with particle size discrimination indicated low levels of respirable dust generation. The SEM analyses revealed that fibers were on average 28 micrometers in length and ranged from 5 to 150 micrometers. CI installers' PBZ samples and area air samples for total dust were significantly higher for dry attic applications than wet attic applications (p < 0.01). Respirable dust air samples collected in the attic area indicated a significantly higher concentration for dry applications than wet applications (p < 0.01). The hopper operators' total dust exposures were significantly higher during wet wall/ceiling applications than dry wall/ceiling applications (p = 0.02). Analysis of variance (ANOVA) tests evaluating exposure concentrations revealed that total dust air samples collected in the PBZ of workers (CI installer in attics, CI installer in walls, hopper operator during attic applications, and hopper operator during walls/ceiling applications) varied significantly during dry applications (p < 0.01). The respirable dust air samples collected in various areas (attic area, hopper area during attic applications, and hopper area during walls/ceiling applications) differed significantly during dry applications (p = 0.03). Twenty-three workers participated in the medical phase of the investigation. The workers completed a medical and work history questionnaire, performed serial peak flow tests, and completed multiple acute symptom surveys. The medical questionnaires indicated respiratory, nasal, and skin symptoms that employees attributed to CI exposure. The most common symptoms reported while working with CI included nasal symptoms (35%), eye symptoms (35%), and morning phlegm production (25%). There was a temporal association between CI exposure and eye symptoms. There is little evidence of lower respiratory system health conditions associated with CI exposure. Based on the air sample data collected from the 10 contractor site visits, NIOSH investigators conclude that there is potential for overexposure to cellulose insulation (CI). Employees in virtually all CI application activities were exposed to total dust levels which exceeded the OSHA 8-hour TWA of 15 mg/m3. CI installers' PBZ total dust samples and area air samples for total and respirable dust were significantly higher for dry attic applications than wet attic applications. Eye symptoms were temporally associated with CI exposure. There is little evidence of lower respiratory tract health conditions associated with CI exposure. Suggestions to improve the health and safety of employees in this industry, through the use of engineering controls and personal protective equipment (i.e., respirators), are presented in the Recommendations section of this report.
Cellulose-fibers; Construction-materials; Construction-workers; Insulation-industry; Insulation-materials; Insulation-workers; Toxicology; Plasterers; Acoustical-materials; Exposure-limits; Hazard-Confirmed; Analytical-methods; Dust-exposure; Fire-proofing; Eye-irritants; Respiratory-irritants; Skin-irritants; Air-sampling