Computational Model of Temperature Elevation in Rats Exposed to Intense and Localized Exposure at 1.5 GHz

There has been increasing public concern about the adverse health effects of human exposure to electromagnetic waves. In the radiofrequency and microwave (MW) ranges, elevated temperature (1-2 C) resulting from energy absorption is known to be a dominant factor inducing adverse health effects such as heat exhaustion and heat stroke. Whole-body average specific absorption rate (SAR) is used as a measure of human protection for MW whole-body exposure. Thresholds are based on the fact that MW exposure of laboratory animals in excess of approximately 4 W/kg has revealed a characteristic pattern of thermoregulatory response. Peak spatially averaged SAR is used as a metric for localized exposure, but the rationale for the use of SAR as a metric for local exposure has been challenged, especially with respect to local and systemic physiological responses, including change in blood perfusion. In order to obtain some insight on the effect of localized exposure, our group has conducted exposures of rats. Our previous studies had failed to show blood flow changes in pial microcirculation in the brain of rats locally exposed to 1,439 MHz RF even at 4.8 W/kg brain averaged SAR (e.g., [1]). On the contrary, a recent study reported that the blood flow in the human brain increased after the exposure to pulse-modulated 900 MHz RF at 0.27 W/kg brain averaged SAR [2]. In the present study, we simulate the exposure scenario of the measurement in [3] in order to investigate the time course of temperature elevation due to microwave exposure.