ID Number		1236
Study Type		Engineering & Physics
Model		900, 1800 MHz (GSM) exposure and modeling of SAR distribution and surface heating using vascularized human FDTD models (including child vs. adult)
Details		Mobile phone exposure (peak SAR over 10 grams) in the heads of adults and children was calculated using FDTD techniques and three adult human models (the head from the "Visible Human" developed by Brooks Air Force Base, a FTRD head model, and a head model developed in the COMOBIO program). The RF source was a handset with a patch antenna transmitting at either 900 or 1800 MHz (constant power). Variability across the different head models was +/- 30% (at 900 MHz SAR ranged from 0.61 to 1.24 W/kg, avg 0.85 W/kg; at 1800 MHz SAR ranged from 0.14 to 0.49 W/kg, avg 0.34 W/kg). The authors also calculated comparative SAR in an adult model (the specific anthropomorophic mannequin [SAM] phantom), a 12 yr old child model (non-uniformly downscaled from an adult by Wang and Fujiwara [2003]), and a 4 yr old child model (developed by Wiart et al for the ADONIS program). There was no adjustment of tissue dielectric properties for the child modeling due to age. Both 900 and 1800 MHz frequencies and three different handset combinations (incorporating a patch, dipole, and quarter wavelength antenna) were used. The authors report the SAM phantom yielded higher SAR values in comparison with the more realistic child-like model (i.e., the current standards are conservative). The average adult-to-child ratio (max SAR / 10 g in the adult vs. child head) was 0.92 +/- 0.17 at 900 MHz and 0.83 +/- 0.12 at 1800 MHz. When SARs were averaged over 1 gram, adult-to-child ratios were 0.98 +/- 0.21 and 0.91 +/- 0.20, respectively. Although the authors report slightly higher SAR values in the child models, they also state that downsizing of tissues in the child-like models disproportionately reduces skin and skull thickness, resulting in potentially over-estimating SAR values. The authors finally report that a fetal MRI model (multilayer model of a pregnant woman) and a 900 MHz, 120 V/m plane wave E-field source resulted in an SAR in the head of the fetus of 0.8 W/kg, and much less at higher frequencies. AUTHORS' ABSTRACT: Wiart et al. 2011 (IEEE #6070): Children are more and more using wireless communication systems. This growth has strengthened public concern and has highlighted the need to assess the radio frequency (RF) exposure of children. In dosimetry, taking advantage of the improvement of High Performance Calculation systems, great efforts have been carried out to improve the numerical tools and human models used to assess the Specific Absorption Rate (SAR). This paper analyses progress in building child and foetus models for numerical dosimetry purpose. The simulation results, in terms of Specific Absorption Rate over 1 and 10 g of tissues, in specific organs such as brain and averaged over the whole body, are reported and analysed. The results show that compliance methods used nowadays to certify phones are valid for children. The studies also show that specific tissues such as peripheral brain tissues can have higher exposure with children than with adults. Studies performed with plane waves as sources and whole body children models show that the whole body SAR of children can be higher than the WBSAR of adults and that the compliance to ICNIRP reference levels does not guarantee the compliance to ICNIRP basic restrictions. Dealing with the foetus models and dielectric properties great efforts have been made. Preliminary results show that the foetus exposure is often lower than the mother exposure, with an important influencing parameter: the foetus position in the uterus. AUTHORS' ABSTRACT: Chiaramello et al. (IEEE #7015): In this study, the exposure of a female eight-year old child to a WLAN access point located in an unknown position in a realistic indoor environment was investigated. A stochastic dosimetry approach based on low rank tensor approximation was used to develop surrogate models to quickly estimate the specific absorption rate in all the possible positions of the WLAN source and the child. Results showed that, for all the possible positions in the room, the exposure values were significantly below the limits of the International Commission of Non-Ionizing Radiation Protection guidelines for general public exposure. The variation of the positions of the source and the child greatly influenced the exposure, resulting in quartile coefficient of dispersion values always higher than 65%. The WLAN source positions, among all the possible ones, that minimize the exposure of the child staying in the rectangular room were found to be on the sides of the smaller wall of the room.
Findings		Effects
Status		Completed With Publication
Principal Investigator		France Telecom, France
Funding Agency		CoMoBio, France, ADONIS, France
Country		FRANCE
References		Wiart, J et al. Bioelectromagnetics, (2005) 26 suppl 7:S19-S30 Hadjem, A et al. Proceedings on IEEE MTT-S International Microwave Symposium IMS, (2004) :- Wiart, J et al. Progress in Biophysics and Molecular Biology., (2011) 107:421-427 Chiaramello, E et al. Journal of Electromagnetics, RF and Microwaves in Medicine and Biology., (2018) 2:131-137 Chiaramello, E et al. Annals of Telecommunications. , (2019) 74:113-121 Tognola, G et al. IEEE Journal of Electromagnetics, RF and Microwaves in Medicine and Biology., (2021) 5:100-107
Comments