Project Abstract
Stage 1 of Data Collection (Spring 1999):
Forty-two noise exposure samples and 166 whole-body (W-B) and hand-arm (H-A) vibration exposures were collected from 43 forestry workers in 6 trades employed by two forestry companies.  Samples were collected on 10 monitoring days over an eight-week period during felling, yarding and landing, road construction, and log handling operations.  Up to five volunteer workers were monitored for noise and vibration each sampling day using datalogging noise dosimeters, which provided both daily TWAs and one-minute averages, and a precision sound level meter equipped to measure human vibration, which provided triaxial H-A and W-B event weighted averages (AEQs) according to ACGIH W-B and H-A TLV criteria.  Workers completed a short questionnaire throughout the workday detailing the timing and number of tasks performed and equipment used.  

The mean for 99 W-B summary weighted AEQs was 5.28 m/s2 (14.21 SD, range 0.03-101.00), while the mean for 67 H-A summary weighted AEQs was 8.30 m/s2 (16.34 SD, range 0.05-96.40).  Comparisons were made between noise exposures measured using the OSHA and NIOSH metrics.  The mean OSHA TWA was 86.1 dBA (6.22 SD, range 71.5-101.5), while the mean NIOSH TWA was 90.2 dBA (5.1 SD, range 81.0-104.7).  Substantial overexposures to both noise and vibration were seen in the population assessed; for example, 60% of OSHA TWAs and 83% of NIOSH TWAs exceeded 85 dBA.  The task and tool associated with the highest noise exposure levels were unbelling chokers on landings and chainsaws, while the task and tool associated with the highest vibration exposure levels were spreading rock with a vehicle and bulldozers (W-B), and notching stumps and chainsaws (H-A).  Trade, task, tool, and operation type were found to be good predictors of noise and vibration exposure levels.  An internal validation substudy indicated excellent agreement between worker-reported and researcher-documented tasks and tools.

Stage 2 of Data Collection (Fall 2001-present):
Fifty-eight workers from 9 logging companies in Washington, Alaska, and Idaho were assessed for noise and vibration (hand-arm and whole-body) over 6 weeks.  Various operations were evaluated, including manual and mechanized falling, harvesting and forwarding, skidding, yarding and landing, processing, log transport, and log sorting/decking.  Seventeen types of equipment were evaluated for noise and vibration.  In addition to participating in noise dosimetry and vibration measurements, workers completed activity cards documenting the timing and frequencies of tasks performed and equipment used, and also answered several questionnaires regarding their health status and current and historical occupational and recreational exposures to noise and vibration.  Questionnaire and measurement data were collected using Personal Digital Assistants (PDAs).  The results of these questionnaires were compared to those from 2 control groups: one (silviculturists) for hand-arm vibration, and another (office workers) for whole-body vibration.

The exposure assessment results indicate that logging workers are routinely exposed to levels of noise and vibration exceeding the OSHA and NIOSH noise standards and the ACGIH and CEC recommendations for hand-arm and whole-body vibration, respectively.  The mean TWA level was 90.2 (7.9 dBA SD) (NIOSH) and 85.5 (8.9 dBA SD) (OSHA); 77% of all NIOSH TWAs exceeded the 85 dBA NIOSH REL, and 27% of OSHA samples exceeded the 90 dBA OSHA PEL.  The highest noise sources were chainsaws, road graders, and front end loaders.  Fifty-seven percent of 259 hand-arm vibration measurements exceeded the ACGIH recommendation of 4 m/s2 for 8-hour shifts, and 75% of 115 whole-body measurements exceeded the CEC 8-hour recommendation of 0.7 m/s2.  The highest hand-arm vibration sources were chainsaws and front end loaders.  The highest whole-body vibration sources were shovels and forwarders.Logging workers were more likely to report vibration-related health effects and work-related hearing loss than were the controls.  These research findings suggest that loggers are frequently overexposed to occupational noise and vibration, and that these overexposures result in adverse health effects.  The research strategy employed allows for identification of risk factors for overexposure; these risk factors can provide guidance for the development of exposure controls.
 

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