Thermoregulatory responses of heat production and heat loss were measured in seven adult volunteers (four women and three men, aged 21–57 yr) during 45‐min dorsal exposures of the whole body to 450 MHz continuous wave radio frequency (RF) fields. Two power densities (PD) (local peak PD = 18 and 24 mW/cm2; local peak specific absorption rate = 0.320 [W/kg]/[mW/cm2]) were tested in each of three ambient temperatures (Ta = 24, 28, and 31 °C) plus Ta controls (no RF). No changes in metabolic heat production occurred under any exposure conditions. Vigorous increases in sweating rate on back and chest, directly related to both Ta and PD, cooled the skin and ensured efficient regulation of the deep body (esophageal) temperature to within 0.1 °C of the normal level. Category judgments of thermal sensation, comfort, sweating, and thermal preference usually matched the measured changes in physiological responses. Some subtle effects related to gender were noted that confirm classic physiological data. Our results indicate that dorsal exposures of humans to a supra‐resonant frequency of 450 MHz at local peak specific absorption rates up to 7.68 W/kg are mildly thermogenic and are counteracted efficiently by normal thermophysiologic heat loss mechanisms, principally sweating. Bioelectromagnetics 19:232–245, 1998. Published 1998 Wiley‐Liss, Inc.
We have examined experimentally the question of increased vulnerability to the thermalizing effects of MW exposure during febrile illness. In a controlled ambient temperature of 26 degrees C, autonomic mechanisms of heat production and heat loss were measured in febrile squirrel monkeys during 30-min exposures to 450 or 2450 MHz CW MW fields at different phases of the fever cycle (induction, plateau, defervescence). We have shown that MW energy absorbed during a febrile episode spares endogenous energy production, but may augment the fever if deposited deep in the body, as is the case during exposure at the resonant frequency. The fever may also be exacerbated if the MW exposure occurs late in the febrile episode, a condition that may put an organism at some risk, especially if the field strength exceeds safety guidelines.
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