Simulation of the temperature elevation in children exposed to plane wave electromagnetic fields (10 MHz-1 GHz) at the ICNIRP reference level.
Because of a lack of thermal models, to date, limitation of exposure to an electromagnetic field (EMF) has been based on restricting intracorporal specific absorption rates. To allow convenient compliance checks, reference field values have been defined. If they are met, compliance with basic restrictions is assumed. This article demonstrates that this assumption is not valid in every case. It has therefore been investigated as to whether the biological goal of limiting tissue heating is still met, in particular with regard to children. The thermal solver applied is based on the bioheat equation, with implemented additional improvements that allow consideration of blood flow and metabolic rate as a function of local tissue temperature rise and, in addition, adapt the blood temperature relative to the absorbed power. As a further improvement, heat exchange at the tissue/air boundary has been modeled, with radiation, convection, and sweating considered as well. The mathematical equations describing these additional thermoregulatory mechanisms were taken from the literature and unified in the thermoregulatory model used for this study. For the investigated case of plane wave exposure, the results confirm the violation of the basic restrictions in five of the six models when exposed to reference EMF levels. However, using thermal modeling, it was possible to demonstrate that heating remained within the biological tolerances. In particular, temperature elevation of the body core temperature remained <0.014°C and the local peak temperature did not exceed 1°C.
Institute of Health Care Engineering, Graz University of Technology, Austria. niedermayr@tugraz.at
Florian
F
Niedermayr
Norbert
N
Leitgeb
Werner
W
Siegl
D001831:Body Temperature / Q000502:physiology* / Q000528:radiation effects*; D002648:Child; D003198:Computer Simulation; D004307:Dose-Response Relationship, Radiation; D004574:Electromagnetic Fields; D004781:Environmental Exposure; D005260:Female; D005858:Germany; D006801:Humans; D008872:Microwaves; D008954:Models, Biological; D011829:Radiation Dosage; D011834:Radiation Monitoring / Q000592:standards*; D011835:Radiation Protection / Q000379:methods; D011846:Radio Waves; D012016:Reference Values