Partial-body exposure of human volunteers to 2450 MHz pulsed or CW fields provokes similar thermoregulatory responses

Many reports describe data showing that continuous wave (CW) and pulsed (PW ) radiofrequency (RF) fields, at the same frequency and average power densi ty (PD), yield similar response changes in the exposed organism. During who le-body exposure of squirrel monkeys at 2450 MHz CW and PW fields, heat pro duction and heat loss responses were nearly identical. To explore this ques tion in humans, we exposed two different groups of volunteers to 2450 MHz C W (two females, five males) and PW (65 mus pulse width, 10(4) pps; three fe males, three males) RF fields. We measured thermophysiological responses of heat production and heat loss (esophageal and six skin temperatures, metab olic heat production, local skin blood flow, and local sweat rate) under a standardized protocol (30 min baseline, 45 min RF or sham exposure, 10 min baseline), conducted in three ambient temperatures (T-a = 24, 28, and 31 de greesC). At each T-a, average PDs studied were 0, 27, and 35 mW/cm(2) (Spec ific absorption rate (SAR) = 0, 5.94, and 7.7 W/kg). Mean data fur each gro up showed minimal changes in core temperature and metabolic heat production for all test conditions and no reliable differences between CW and PW expo sure. Local skin temperatures showed similar trends for CW and PW exposure that were PD-dependent; only the skin temperature of the upper back (facing the antenna) showed a reliably greater increase (P = .005) during PW expos ure than during CW exposure. Local sweat rate and skin blood flow were both T-a- and PD-dependent and showed greater variability than other measures b etween CW and PW exposures; this variability was attributable primarily to the characteristics of the two subject groups. With one noted exception, no clear evidence for a differential response to CW and PW fields was found. (C) 2001 Wiley-Liss,Inc.