Study of Occupational Magnetic Field Personal Exposures Associated with Seattle Metro Transit's Electric Trolley System

摘要

This study characterized the occupational exposures to magnetic fields of workers employed in the electric trolley operations of Metro Transit, the agency that operates the public transportation system in and around the City of Seattle. From the approximately 700 individuals employed in this division of Metro Transit, 104 holding 18 different job titles were selected for sampling. Volunteer workers were asked to wear Emdex II or Emdex Lite magnetic-field meters at a waist location for one work shift. Emdex II meters were set to record the broadband (40-800 Hz) and harmonic (100-800 Hz) magnetic fields sampled every 3 s. Emdex Lite meters were programmed to record the broadband (40-1000 Hz) magnetic field every 4 s. Using the resulting data the following nine exposure metrics were calculated: Time-weighted-average broadband personal magnetic-field exposure; time-weighted-average harmonic personal magnetic-field exposure; 90th percentile broadband personal magnetic-field exposure; 95th percentile broadband personal magnetic-field exposure; fraction of broadband measurements > 2 mG; fraction of broadband measurements > 5 mG; fraction of broadband measurements > 10 mG; temporal broadband magnetic-field variability using the RCM metric; temporal broadband magnetic-field variability using the RCM metric.