Measurement and Exposure Assessment of Intermediate Frequency Magnetic Fields From Electronic Article Surveillance (EAS) Gates in Libraries

Abstract

Exposure to magnetic fields from the electronic article surveillance (EAS) gate was evaluated in consideration of the application to epidemiological studies of library workers who are exposed continually to intermediate frequency magnetic fields from the EAS gate. Two types of exposures were investigated. One was transient exposure due to passing through or beside the gate and another was chronic exposure in the room. We measured magnetic fields from five EAS gate models which were commonly used in libraries in Japan. Detailed measurements were performed for two of them in consideration of the phase difference of vector components of magnetic flux density. The polarization of the magnetic field in the gate was investigated with the index of ellipticity. The induced electric field in a human body was numerically calculated for exposures to magnetic fields of the two gate models. The results provide a quantitative understanding of exposures during passing through or by the EAS gate. Magnetic field distribution was measured in a large room for one gate model to quantify the chronic exposure of library workers during the work at the desk. It was found that the magnetic field was distributed as a function of the horizontal distance to the nearest gatepost. The 45-point average value BIEC defined by the IEC standard was suggested to be a useful quantity to characterize the magnitude of the magnetic field from the EAS gate. Exposures to different EAS gates are expected to be compared through this quantity without detailed measurements. These results are expected to provide useful means for exposure assessment of epidemiological studies on the association between the IF-EMF exposure and possible health outcomes.

Assessment of combined exposure to intermediate-frequency electromagnetic fields and pulsed electromagnetic fields among library workers in Japan

“…The employed measurement method and exposure assessment results were described in the abovementioned study ( 18 ). Firstly, the magnetic fields of the gates were measured in accordance with IEC 62369-1 ( 24 ), which provides a recommended measurement method for evaluating exposure from short-range devices (including EAS gates).…”

“…The 45-point average of the magnetic field ( B IEC ) provides an index of the magnitude of the magnetic field originating from the EAS gate according to the procedure delineated by the IEC 62369-1 ( 24 ). The characteristics of distance decay as a function of the distance to the gate were generalized based on the normalized three-dimensional magnetic field distribution of the measured area, That is, the exposure level at the seated position for each respondent was estimated using Equation (1) ( 18 ), as follows:…”

“…To assess E2, numerical calculations using the impedance method and incorporating complex variables were implemented herein ( 18 ). Briefly, to estimate the exposure upon passing through or beside an EAS gate, the induced electric fields in a human body model inside gate II were calculated.…”

“…Our group has previously reported research findings regarding the measurement and exposure assessment of intermediate frequency magnetic fields originating from EAS systems in libraries ( 18 ). More specifically, this previous study investigated two types of exposures: transient exposures due to passing through or beside EAS gates, and continuous exposures in the room.…”

“…For exposure assessment, the results of previous studies were used to generate exposure estimates in combination with answers to the questionnaire survey that was administered in the current study. EAS exposures were also partially estimated using the results of the abovementioned previous study by our group ( 18 ). The numerical analyses reported herein were newly performed for BCUs.…”