Electronic Article Surveillance Devices Research Articles

A pilot study on the reproductive risks of maternal exposure to magnetic fields from electronic article surveillance systems

Purpose: We investigated the feasibility of a large-scale epidemiological study on reproductive effects of intermediate frequency (IF) magnetic field (MF) exposure among cashiers working near electronic article surveillance (EAS) systems.Materials and methods: The study cohort included 4157 women who had worked as cashiers in supermarkets with EAS devices (considered as exposed) or grocery stores without EAS devices (considered as unexposed) between 2008 and 2015. 536 births and 38 miscarriages occurred among these women during the study period, based on information from nationwide health registries. Measurements were also performed to characterize the MF exposure of cashiers.Results: Cashiers were found to be exposed to 8.2 MHz MFs only when passing by the gates at short distance. Static fields of about 0.1 mT were observed at cashier’s seat. Extremely low frequency MFs were higher at stores without EAS devices. No differences on the risk of miscarriage, reduced birth weight or preterm birth were observed between cashiers in different store types.Conclusions: Any further studies should attempt to include study subjects working near EAS systems that produce stronger IF MFs at kHz frequencies. Exposure to ELF MFs should be assessed as a possible confounding factor.

Occupational exposure to intermediate frequency and extremely low frequency magnetic fields among personnel working near electronic article surveillance systems

Cashiers are potentially exposed to intermediate frequency (IF) magnetic fields at their workplaces because of the electronic article surveillance (EAS) systems used in stores to protect merchandise against theft. This study aimed at investigating occupational exposure of cashiers to IF magnetic fields in Finnish stores. Exposure to extremely low frequency (ELF) magnetic fields was also evaluated because cashiers work near various devices operating with 50 Hz electric power. The peak magnetic flux density was measured for IF magnetic fields, and was found to vary from 0.2 to 4 µT at the cashier's seat. ELF magnetic fields from 0.03 to 4.5 µT were found at the cashier's seat. These values are much lower than exposure limits. However, according to the International Commission on Non-Ionizing Radiation Protection (ICNIRP) occupational reference levels for IF magnetic fields (141 µT for the peak field) were exceeded in some cases (maximum 189 µT) for short periods of time when cashiers walked through the EAS gates. As the ICNIRP reference levels do not define any minimum time for exposure, additional investigations are recommended to determine compliance with basic restrictions. Even if the basic restrictions are not exceeded, persons working near EAS devices represent an exceptional group of workers with respect to exposure to electromagnetic fields. This group could serve as a basis for epidemiological studies addressing possible health effects of IF magnetic fields. Compliance with the reference levels for IF fields was evaluated using both broadband measurement of peak fields and the ICNIRP summation rule for multiple frequencies. The latter was generally more conservative, and the difference between the two methods was large (>10-fold) for EAS systems using a 58 kHz signal with complex waveform. This indicates that the ICNIRP multiple frequency rule can be unnecessarily conservative when measuring complex waveforms.

Comparison of SAR and induced current densities in adults and children exposed to electromagnetic fields from electronic article surveillance devices

Electronic article surveillance (EAS) devices are widely used in most stores as anti-theft systems. In this work, the compliance with international guidelines in the human exposure to these devices is analysed by using the finite-difference time-domain (FDTD) method. Two sets of high resolution numerical phantoms of different size (REMCOM/Hershey and Virtual Family), simulating adult and child bodies, are exposed to a 10 MHz pass-by panel-type EAS consisting of two overlapping current-carrying coils. Two different relative positions between the EAS and the body (frontal and lateral exposures), which imply the exposure of different parts of the body at different distances, have been considered. In all cases, induced current densities in tissues of the central nervous system and specific absorption rates (SARs) are calculated to be compared with the limits from the guidelines. Results show that induced current densities are lower in the case of adult models as compared with those of children in both lateral and frontal exposures. Maximum SAR values calculated in lateral exposure are significantly lower than those calculated in frontal exposure, where the EAS–body distance is shorter. Nevertheless, in all studied cases, with an EAS driving current of 4 A rms, maximum induced current and SAR values are below basic restrictions.

Calculation of magnetic field-induced current densities for humans from EAS countertop activation/deactivation devices that use ferromagnetic cores

Compliance testing of electronic article surveillance (EAS) devices requires that induced current densities in central nervous system (CNS) tissues, i.e. brain and the spinal cord, be less than the prescribed safety limits. Even though ferromagnetic cores are mostly used for activation/deactivation of embedded magnetic tags, assumed equivalent air-core coils with guessed increased number of ampere turns have always been used to calculate the magnetic fields for the proximal region to which a customer is exposed. We show that at low frequencies up to several kilohertz, duality of electric and magnetic circuits may be exploited such that the shaped high reluctance core is modelled as though it was a higher conductivity electric circuit of the corresponding shape. The proposed procedure is tested by examples of two magnetic cores typical of countertop activation/deactivation devices. The equivalent exposure magnetic fields obtained from the dual electric fields are shown to be in excellent agreement (within ±5%) with those measured for these ferromagnetic EAS devices. The previously proposed impedance method is then used to calculate the induced current densities for a 1.974 × 1.974 × 2.93 mm resolution anatomic model of a human. For the two considered EAS systems using excitation currents of 5000 A turns at 200 Hz, the maximum 1 cm2 area-averaged induced current densities in the CNS tissues are calculated and found to be less than the ICNIRP safety limits.

Calculation of induced current densities for humans by magnetic fields from electronic article surveillance devices

This paper illustrates the use of the impedance method to calculate the electric fields and current densities induced in millimetre resolution anatomic models of the human body, namely an adult and 10- and 5-year-old children, for exposure to nonuniform magnetic fields typical of two assumed but representative electronic article surveillance (EAS) devices at 1 and 30 kHz, respectively. The devices assumed for the calculations are a solenoid type magnetic deactivator used at store checkouts and a pass-by panel-type EAS system consisting of two overlapping rectangular current-carrying coils used at entry and exit from a store. The impedance method code is modified to obtain induced current densities averaged over a cross section of 1 cm2 perpendicular to the direction of induced currents. This is done to compare the peak current densities with the limits or the basic restrictions given in the ICNIRP safety guidelines. Because of the stronger magnetic fields at lower heights for both the assumed devices, the peak 1 cm2 area-averaged current densities for the CNS tissues such as the brain and the spinal cord are increasingly larger for smaller models and are the highest for the model of the 5-year-old child. For both the EAS devices, the maximum 1 cm2 area-averaged current densities for the brain of the model of the adult are lower than the ICNIRP safety guideline, but may approach or exceed the ICNIRP basic restrictions for models of 10- and 5-year-old children if sufficiently strong magnetic fields are used.

Electromagnetic field strength levels surrounding electronic article surveillance (EAS) systems.

Electronic article surveillance (EAS) is used in many applications throughout the world to prevent theft. EAS systems produce electromagnetic (EM) energy around exits to create an EM interrogation zone through which protected items must pass before leaving the establishment. Specially designed EAS tags are attached to these items and must either be deactivated or removed prior to passing through the EAS EM interrogation zone to prevent the alarm from sounding. Recent reports in the scientific literature have noted the possibility that EM energy transmitted by EAS systems may interfere with the proper operation of sensitive electronic medical devices. The Food and Drug Administration has the regulatory responsibility to ensure the safety and effectiveness of medical devices. Because of the possibility of electromagnetic interference (EMI) between EAS systems and electronic medical devices, in situ measurements of the electric and magnetic fields were made around various types of EAS systems. Field strength levels were measured around four types of EAS systems: audio frequency magnetic, pulsed magnetic resonant, radio frequency, and microwave. Field strengths from these EAS systems varied with magnetic fields as high as 1073.6 Am(-1) (in close proximity to the audio frequency magnetic EAS system towers), and electric fields up to 23.8 Vm(-1) (in close proximity to the microwave EAS system towers). Medical devices are only required to withstand 3 Vm(-1) by the International Electrotechnical Commission's current medical device standards. The modulation scheme of the signal transmitted by some types of EAS systems (especially the pulsed magnetic resonant) has been shown to be more likely to cause EMI with electronic medical devices. This study complements other work in the field by attaching specific characteristics to EAS transmitted EM energy. The quantitative data could be used to relate medical device EMI with specific field strength levels and signal waveforms. This is one of several efforts being made by the FDA, the electronic medical device industry and the EAS industry to mitigate the potential for EMI between EAS and medical devices.

The effects of electronic article surveillance systems on permanent cardiac pacemakers: an in vitro study.

Five Siemens Pacesetter cardiac pacemakers (PM) were subjected to in vitro testing with six different electronic article surveillance (EAS) devices. The PMs consisted of polarity programmable, dedicated bipolar, and dedicated unipolar types. EAS equipment included UHF, RF, Magnetic, and Magnetoacoustic (MA) devices from two manufacturers. Prior to testing, each PM was interrogated and normal operation confirmed. Each PM was attached to a heart simulator via an eight foot cable and then subjected to testing within the EAS field. The PMs were passed through the field in two axes, positioned stationary within the field, and, worst case (WC), placed directly against the transmitter. During testing the ECG was observed and PM behavior recorded. In one PM (Synchrony III), Event Records, and Event Histograms were utilized. At the conclusion of testing with each EAS device the PM was evaluated for normal operation. No PM was reprogrammed by the EAS devices. UHF produced no effect on the PMs. RF produced noise response in one unipolar PM while in the WC position. High frequency and multifrequency magnetic units produced positive results only in the WC position. Unipolar PMs were affected more often than bipolar. MA and older magnetic EAS units produced more positive responses than newer lower power devices. One incident of close coupled (400 msec) ventricular pacing was seen with the MA EAS unit. UHF, RF, high frequency, and dual frequency magnetic EAS produced few effects during in vitro testing. Except with the MA and low frequency magnetic devices, positive results occurred only in WC conditions.(ABSTRACT TRUNCATED AT 250 WORDS)