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 ele ctric fields and current densities induced in millimetre resolution anatomi c 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 rep resentative 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 s ystem consisting of two overlapping rectangular current-carrying coils used at entry and exit from a store. The impedance method code is modified to o btain induced current densities averaged over a cross section of 1 cm(2) pe rpendicular to the direction of induced currents. This is done to compare t he peak current densities with the limits or the basic restrictions given i n the ICNIRP safety guidelines. Because of the stronger magnetic fields at lower heights for both the assumed devices, the peak 1 cm(2) 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 mod el of the 5-year-old child. For both the EAS devices, the maximum I cm2 are a-averaged current densities for the brain of the model of the adult are lo wer than the ICNIRP safety guideline, but may approach or exceed the ICNIRP basic restrictions for models of 10- and 5-year-old children if sufficient ly strong magnetic fields are used.