The effect of increase in dielectric values on specific absorption rate (SAR) in eye and head tissues following 900, 1800 and 2450 MHz radio frequency (RF) exposure

Technology Platforms, Nokia Corporation, PO Box 301, FIN-00045 Nokia Group, Linnoitustie 6, 02600 Espoo, Finland.
Physics in Medicine and Biology (Impact Factor: 2.76). 04/2006; 51(6):1463-77. DOI: 10.1088/0031-9155/51/6/007
Source: PubMed


Numerous studies have attempted to address the question of the RF energy absorption difference between children and adults using computational methods. They have assumed the same dielectric parameters for child and adult head models in SAR calculations. This has been criticized by many researchers who have stated that child organs are not fully developed, their anatomy is different and also their tissue composition is slightly different with higher water content. Higher water content would affect dielectric values, which in turn would have an effect on RF energy absorption. The objective of this study was to investigate possible variation in specific absorption rate (SAR) in the head region of children and adults by applying the finite-difference time-domain (FDTD) method and using anatomically correct child and adult head models. In the calculations, the conductivity and permittivity of all tissues were increased from 5 to 20% but using otherwise the same exposure conditions. A half-wave dipole antenna was used as an exposure source to minimize the uncertainties of the positioning of a real mobile device and making the simulations easily replicable. Common mobile telephony frequencies of 900, 1800 and 2450 MHz were used in this study. The exposures of ear and eye regions were investigated. The SARs of models with increased dielectric values were compared to the SARs of the models where dielectric values were unchanged. The analyses suggest that increasing the value of dielectric parameters does not necessarily mean that volume-averaged SAR would increase. Under many exposure conditions, specifically at higher frequencies in eye exposure, volume-averaged SAR decreases. An increase of up to 20% in dielectric conductivity or both conductivity and permittivity always caused a SAR variation of less than 20%, usually about 5%, when it was averaged over 1, 5 or 10 g of cubic mass for all models. The thickness and composition of different tissue layers in the exposed regions within the human head play a more significant role in SAR variation compared to the variations (5-20%) of the tissue dielectric parameters.

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    • "Now a day's various types of antennas are widely used for wireless communications applications [1]-[5]. The public concern regarding possible health hazards have been growing due to the absorption of electromagnetic energy from the radiation of antennas [6]. The rate of energy absorption by an object when exposed to electromagnetic fields is measured in terms of Specific Absorption Rate (SAR). "
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    ABSTRACT: In this paper a parametric study on characteristics of a planar metal antenna in vicinity of a homogenous human head at 900 MHz and 1800 MHz are carried out. Initially the planar metal antenna is designed at 900 MHz and 1800 MHz. The impedance and radiation characteristics of these antennas are shown in free space and in proximity of a human head. Also Specific Absorption Rate (SAR) for different distances of the antenna from head are evaluated and compared.
    C3IT 2012, Academy of Technology, Hooghly, West Bengal, India; 02/2015
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    • "Dr. Giorgi Bit-Babik in our laboratory, in collaboration with Dr. Guy, Professor Jian-qin Wang, and Professor Osamu Fujiwara of Nagoya Institute of Technology, tested several human head models and found that penetration depths for children and adults are about the same [Bit- Babik et al., 2005]. This conclusion is consistent with other recent publications [Martinez-Burdalo et al., 2004; Christ and Kuster, 2005; Lee et al., 2005; Wiart et al., 2005; Beard et al., 2006; Keshvari et al., 2006]. "

    • "Being fatty, myelin does not contain free ions. Keshvari et al. (2006) postulated that this indicates that as the myelin sheath develops there is also a reduction in electrical conductivity of brain tissue. The reverse side of this coin is "
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    ABSTRACT: Myelin provides the electrical insulation for the central and peripheral nervous system and develops rapidly in the first years of life, but continues into mid-life or later. Myelin integrity is vital to healthy nervous system development and functioning. This review outlines the development of myelin through life, and then considers the evidence for an association between myelin integrity and exposure to low-intensity radiofrequency electromagnetic fields (RF-EMFs) typical in the modern world. In RF-EMF peer-reviewed literature examining relevant impacts such as myelin sheath, multiple sclerosis, and other myelin-related diseases, cellular examination was included. There are surprisingly little data available in each area, but considered together a picture begins to emerge in RF-EMF-exposed cases: (1) significant morphological lesions in the myelin sheath of rats; (2) a greater risk of multiple sclerosis in a study subgroup; (3) effects in proteins related to myelin production; and (4) physical symptoms in individuals with functional impairment electrohypersensitivity, many of which are the same as if myelin were affected by RF-EMF exposure, giving rise to symptoms of demyelination. In the latter, there are exceptions; headache is common only in electrohypersensitivity, while ataxia is typical of demyelination but infrequently found in the former group. Overall, evidence from in vivo and in vitro and epidemiological studies suggests an association between RF-EMF exposure and either myelin deterioration or a direct impact on neuronal conduction, which may account for many electrohypersensitivity symptoms. The most vulnerable are likely to be those in utero through to at least mid-teen years, as well as ill and elderly individuals.
    Journal of Toxicology and Environmental Health Part B 09/2014; 17(5):247-58. DOI:10.1080/10937404.2014.923356 · 4.97 Impact Factor
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