Characterization of Extremely Low Frequency Magnetic Field Exposures of Office Workers

Abstract

The purpose of this study is to present results of an extremely low frequency magnetic field exposure assessment performed in a large office building environment. The extremely low frequency magnetic field assessment strategy included an evaluation of full-shift personal exposure for building occupants, a determination of average work area magnetic fields, and magnetic field characterizations of sources within each work area. An employee questionnaire regarding daily utilization patterns of workplace magnetic field sources was also used to help interpret exposure information. Magnetic field exposures were determined using EMDEX magnetic field exposure meters. For personal magnetic field characterization, each participant wore the monitor for a full shift, and office area magnetic fields were determined as the average of five equally spaced measurements. In situ source characterization included measuring magnetic fields at 30 and 50 cm from pieces of electrical equipment. 259 employees in the building under investigation agreed to participate in the exposure assessment. Personal and area extremely low frequency magnetic field exposures were low, averaging 1.0 ± 1.1 mG (n = 247) and 0.8 ± 0.6 mG (n = 253), respectively. In general, area magnetic field measurements were statistically lower than daily personal magnetic field exposures. The results of this investigation indicate that, except for individuals who routinely pass through a static field created by a book theft device in an on-site library during their workday, personal exposures were not strongly influenced by the number and types of equipment used or the floor on which a person worked.