Electromagnetic Fields: Human Safety Issues

Most of the recently revised safety standards worldwide are set in terms of internal rates of electromagnetic energy deposition (specific absorption rates or SAR) at radio frequencies (RF) and microwave frequencies, and of induced electric fields or current densities at lower frequencies up to 10 MHz. Numerical methods have been developed that use millimeter resolution anatomically based models of the human body to determine SAR or the induced electric fields and current densities for real-life EM exposure conditions. A popular method for use at RF and microwave frequencies is the finite-difference time-domain method. This method is described and illustrated for SAR distributions due to cellular telephones for head models based on human anatomy. A method often used for calculations of induced electric fields and current densities at low frequencies is the impedance method. Use of this method is illustrated by an example of an electronic article surveillance (EAS) system for anatomic models of an adult and 10- and 5-year-old children. Experimental phantoms using a fluid to simulate the dielectric properties of the brain may be used for determination of peak 1- or 10-g SAR needed for compliance with the various safety standards.