Microwave Radiation and Thermoregulation.

Adair, E. R.

doi:10.21236/ada111244

Cited by 2 publications

(7 citation statements)

References 31 publications

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“…When A rfr is added to M in the calculation of tissue conductance, K rises across the full range of power density explored. Thus, at a T of 26 *C, the principal effect of a microwave exposure is an increase in K, or blood flow, a conclusion already reached in the earlier study (4).…”

Section: Abdomen ------------Tabd Tail ---------------Ttl Leg -------supporting

confidence: 69%

“…During the equilibration period, M was slightly elevated above the resting level; the local Tsk indicated that the tail skin was partially vasodilated but that the foot was vasoconstricted ; T stabilized at about 37 *C; and E was 2 ) in the earlier study (4). Each point plotted at zero power density represents the initial equilibrated value for one monkey, coded by symbol, in a single experiment; the steady-state value of that variable during microwave exposure is plotted at the appropriate power density.…”

Section: Abdomen ------------Tabd Tail ---------------Ttl Leg -------mentioning

confidence: 62%

“…Substituting in Equation (2) yields M h ( Tk Ta) +E (4) in which h is the only unknown. This coefficient can be determined at any given T from the relation…”

Section: 16 1mentioning

confidence: 99%

“…Under these conditions, the monkeys could maintain thermal balance indefinitely The purpose of Experiment 3, as described in the general introduction to this report, was to determine similar tolerance limits for autonomic thermoregulation of the squirrel monkey in other environments, viz T a -20 and 26 *C, a using the method of partitional calorimetry. These T a were selected because they are representative of cool and neutral environments for the subject animal (56) and extensive data had been collected at these T a in a previous study (4).…”

Section: Introductionmentioning

confidence: 99%

“…When a squirrel monkey is exposed at a frequency of 2450 MHz, there is the potential for selective focussing of absorbed energy near the center of the head where the PO/AR is located. Experiments that involved independent control of P0/AH temperature, in addition to its measurement, revealed that, while small temperature increments in this area are involved in the initiation of thermoregulatory responses, thermal changes in the body as a whole are of far greater importance to long-term thermoregulation during exposure to microwaves Recent experiments in our laboratory have involved use of the method of partitional calorimetry to study the autonomic thermoregulatory responses of animals exposed to microwaves (4). This method permits a complete accounting of all the sources of thermal energy influencing the individual thermoregulatory mechanisms of the body as well as the specification of the exact means by which energy is transferred from the body to the environment.…”

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confidence: 99%

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Microwave Challenges to the Thermoregulatory System,

Adair¹

1987

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Approved for public release; distribution is unlimited. 10 Thermoregulation Prepared for USAF SCHOOL OF AEROSPACE MEDICINE S9. ABSTRACT (Continue on reverse if necessary and identify by block number)Three experiments were conducted to measure the upper tolerance limit for maintaining thermal balance in squirrel monkeys during exposure to 2450-MHz radiofrequency radiation (RFR). During microwave exposure at high intensity, thermoregulatory behavior, metabolic, vasomotor, and sudomotor responses were mobilized in normal fashion, but the capacity to lose heat through sweating was found to be the limiting factor in microwave tolerance. The major conclusion drawn from these studies is that the thermoregulatory system deals with energy absorbed from microwave fields in exactly the same way as energy produced in the body by normal metabolic processes or absorbed during exposure to conventional radiant or convective heat sources. i UNCLASSIFIED SUMMARYExposure to low-intensity radiofrequency (RF) fields influences the normal responses, both autonomic and behavioral, that regulate the body temperature.In the past, we have used the squirrel monkey as an animal model to determine the minimal incident energy (in mW/cm 2 ) derived from 2450-M z continuous wave (CW) microwaves that is necessary to lower an elevated metabolic heat production in the cold, alter peripheral vasomotor tone in thermoneutral environments, initiate sweating in the heat, and alter thermoregulatory behavior. In all cases, the threshold power density is remarkably similar (4-8 mW/cm 2 ), a finding that suggests a common thermal basis for the response changes. The whole-body specific absorption rate (SAR) at threshold is equivalent to 15-20Z of the resting metabolic heat production (M_) of the subject animal. Above the threshold level, at least to SARa equivalent to two-thirds resting !!, the mobilized thermoregulatory responses ensure that the body temperature is regulated with precision at the normal level and the magnitude of the response change is usually a linear function of field strength. The three experimentsreported here sought to determine the upper limit of these functions, that is, the ceiling intensity that can be effectively dealt with by normal thermoregulatory processes.Experiment 1 measured changes in ambient temperature (T a ) selected by highly trained squirrel monkeys during both transient (10 min) and steady-state (90 min) whole-body microwave exposures at high power densities (up to 70 mw/cmW 2 ). During transient exposures, all power densities tested were countered by behavioral selection of a cooler environment so that the body temperatures were regulated at close to the normal level; 45 mW/cm 2 was similarly well tolerated by all animals in the steady-state. Thus, no upper tolerance limit was found for behavioral thermoregulation.Experiment 2 assessed the potential for disruption of autonomic thermoregulation by an altered metabolic state (induced by injections of isoproterenol) in squirrel monkeys exposed to microwaves in a ther...

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Section: Abdomen ------------Tabd Tail ---------------Ttl Leg -------supporting

confidence: 69%

Section: Abdomen ------------Tabd Tail ---------------Ttl Leg -------mentioning

confidence: 62%

“…Substituting in Equation (2) yields M h ( Tk Ta) +E (4) in which h is the only unknown. This coefficient can be determined at any given T from the relation…”

Section: 16 1mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Microwave Challenges to the Thermoregulatory System,

Adair¹

1987

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Metabolic and vasomotor responses of rhesus monkeys exposed to 225‐MHz radiofrequency energy

Lotz

Saxton

1987

Bioelectromagnetics

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A previous study showed a substantial increase in the colonic temperature of rhesus monkeys (Macaca mulatta) exposed to radiofrequency (RF) fields at a frequency near whole-body resonance and specific absorption rates (SAR) of 2-3 W/kg. The present experiments were conducted to determine the metabolic and vasomotor responses during exposures to similar RF fields. We exposed five adult male rhesus monkeys to 225 MHz radiation (E orientation) in an anechoic chamber. Oxygen consumption and carbon dioxide production were measured before, during, and after RF exposure. Colonic, tail and leg skin temperatures were continuously monitored with RF-nonperturbing probes. The monkeys were irradiated at two carefully-controlled ambient temperatures, either cool (20 degrees C) or thermoneutral (26 degrees C). Power densities ranged from 0 (sham) to 10.0 mW/cm2 with an average whole-body SAR of 0.285 (W/kg)/(mW/cm2). We used two experimental protocols, each of which began with a 120-min pre-exposure equilibration period. One protocol involved repetitive 10-min RF exposures at successively higher power densities with a recovery period between exposures. In the second protocol, a 120-min RF exposure permitted the measurement of steady-state thermoregulatory responses. Metabolic and vasomotor adjustments in the rhesus monkey exposed to 225 MHz occurred during brief or sustained exposures at SARs at or above 1.4 W/kg. The SAR required to produce a given response varied with ambient temperature. Metabolic and vasomotor responses were coordinated effectively to produce a stable deep body temperature. The results show that the thermoregulatory response of the rhesus monkey to an RF exposure at a resonant frequency limits storage of heat in the body. However, substantial increases in colonic temperature were not prevented by such responses, even in a cool environment.

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Microwave Radiation and Thermoregulation.

Cited by 2 publications

References 31 publications

Microwave Challenges to the Thermoregulatory System,

Microwave Challenges to the Thermoregulatory System,

Metabolic and vasomotor responses of rhesus monkeys exposed to 225‐MHz radiofrequency energy

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