New approach to safety evaluation of human exposure to stochastically-varying electromagnetic fields

In this paper, high-frequency (HF) and microwave electromagnetic (EM) fields in experimental fusion facilities were statistically measured, and the exposure levels were compared with safety guidelines to ensure workers´ safety. Since leaked EM fields have time-varying characteristics whose amplitudes vary according to a stochastic process, a measurement of their amplitude probability distribution (APD) was conducted. An approach was then presented to derive from the measured APD the specific absorption rate (SAR) in an exposed human body. The statistically-averaged whole-body-averaged SAR showed that the leaked field intensities were low enough to not cause any thermal hazards for the workers in the specific EM environment. The statistically averaged SAR also showed fair agreement with the SAR derived from the time average over 6 min as specified in the safety guidelines. This finding suggests the usefulness of the APD measurement in lieu of a field measurement over a 6-min period because the APD can be obtained in a time period much less than 6 min.