Article

Yes the Children Are More Exposed to Radiofrequency Energy From Mobile Telephones Than Adults

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Abstract

Our reports of published research in several of the peer-reviewed journal articles in 1996, 2002, and 2004 have generated a lot of controversy over the last two decades, including the most recent publication by Foster and Chou. In this paper, we present arguments based on physics that the main reason for higher exposure of children (also women and men with smaller heads and likely thinner pinnae) to radiofrequency energy from mobile phones is the closer placement of the cell phone radiation source by several millimeters to the tissues of the head, e.g., the brain. Using heterogeneous anatomically derived shaped models of the head, we have previously reported that the exposure increases by a compounding rate of 10%–15% for every single millimeter of closer location of the radiating antenna. This is similar to the report of $sim 20$ % increase for every millimeter in the Foster and Chou’s paper from their (1) even though their simplistic (1) is valid only for a homogenous tissue slab of infinite size and the radiation source that is a wire dipole rather than a mobile telephone. Both of their assumptions for (1) are obviously not applicable for human exposures to mobile telephones. Actually, the physical reason for such a rapid drop off of coupled energy is that the radiofrequency electromagnetic fields close to a radiating source in the so-called near-field region reduce in strength very rapidly with every millimeter of distance, even faster than in the far-field region, where the electromagnetic fields reduce inversely with the square of the distance from the source.

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... Another thing to observe from the data in columns 4 and 5 is that the SAR is higher by a factor of 2 to 3 for a 5-millimeter closer placement of the wireless device. In [6] we have also proposed this as the reason for a higher SAR for children and for women and men with thinner pinna and skulls resulting in radiating wireless devices being placed closer to the brain in stronger radiated EM fields. ...
... 1) The ICNIRP guidelines state that the 10-g SAR for conditions of actual use be no more than 2 W/kg and FCC requires compliance with IEEE Standard C95.1-1991 [1] which is set in terms of 1 g SAR of 1.6 W/kg. It has been shown in peer-reviewed published literature [4], [6] that because of the fairly shallow penetration of RF energy coupled to the tissues, the 1 g SAR is typically 2.5-3 times the 10-g SAR. 2) For cell phones held against the pinna, the measured 1 or 10 g SAR will also be much higher if SAM had not used the lossless artificial plastic spacer in lieu of the tissue-simulant human pinna. As pointed out in [5] and [6], the tapered plastic spacer artificially separates the radiating cell phone antenna by up by up to 10 mm additional spacing for the RF coupled regions of the head resulting in underestimation the 1 g and 10 g SAR by a factor to 2-4. ...
... It has been shown in peer-reviewed published literature [4], [6] that because of the fairly shallow penetration of RF energy coupled to the tissues, the 1 g SAR is typically 2.5-3 times the 10-g SAR. 2) For cell phones held against the pinna, the measured 1 or 10 g SAR will also be much higher if SAM had not used the lossless artificial plastic spacer in lieu of the tissue-simulant human pinna. As pointed out in [5] and [6], the tapered plastic spacer artificially separates the radiating cell phone antenna by up by up to 10 mm additional spacing for the RF coupled regions of the head resulting in underestimation the 1 g and 10 g SAR by a factor to 2-4. This factor of 2-4 higher SAR is also borne out by the ANFR the ANFR measured results in Table 1 where higher values of SAR are reported in columns 3 and 4 that are for separation distances of 15 and 5 mm respectively. ...
Article
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In our publications, we have shown both from measurements and computer modeling that the specific absorption rate (SAR) reduces by 10%–15% for every millimeter separation of the cell phone on account of rapidly diminishing EM fields in the near-field region of the cell phone antenna. This rapid reduction of SAR depending on the antenna and its location on the handset has been shown, both computationally and experimentally, regardless of the phantom model such as a flat phantom suggested for SAR compliance testing of devices in contact with the body, for a sphere phantom, and for head-shaped models used for SAR compliance testing of cell phones. Unfortunately, our observations in the past were based on SARs of only three cell phones. Expecting that the SARs for cell phones may exceed the safety limits for body contact, cell phone manufacturers have started to recommend that the devices can be used at 5–25 mm from the body even though it is difficult to see how to maintain this distance correctly under mobile conditions. The National Agency ANFR of France recently released the cell phone SAR test data for 450 cell phones that measure 10-g SARs reducing by 10%–30% for each millimeter distal placement from the planar body phantom. Their data corroborate our findings that most cell phones will exceed the safety guidelines when held against the body by factors of 1.6–3.7 times for the European/ICNIRP standard or by factors as high as 11 if 1-g SAR values were to be measured as required by the U.S. FCC.
... That critique, which we only became aware of recently, has resulted in allegations that we misrepresented the papers we reviewed and has attracted media attention. We also respond to a separate critique by Gandhi [3] of our paper. ...
... Gandhi [3] raises different issues. He states that ''. . . the main reason for higher exposure of children (also women and men with smaller heads and likely thinner pinnae) to radiofrequency energy from mobile phones is the closer placement of the cell phone radiation source by several millimeters to the tissues of the head, e.g., the brain.' ' Gandhi has been voicing similar concerns for many years, mostly in connection with his view that SAM underestimates exposure. ...
... He states that ''. . . the main reason for higher exposure of children (also women and men with smaller heads and likely thinner pinnae) to radiofrequency energy from mobile phones is the closer placement of the cell phone radiation source by several millimeters to the tissues of the head, e.g., the brain.' ' Gandhi has been voicing similar concerns for many years, mostly in connection with his view that SAM underestimates exposure. His focus on methodology for compliance assessment is also evident in [3]. However, the studies we cited above and in [2] (which Gandhi does not dispute) clearly undercut his position, at least with regard to the conservative nature of SAM for estimating psSAR (head) for compliance assessment. ...
Article
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This is a response to two critical comments on our 2014 paper in the IEEE Access. That paper reviewed numerical dosimetry/modeling studies on the exposure [in terms of specific absorption rate (SAR)] to the user of a mobile phone to radiofrequency energy, and possible differences in exposure to children versus adults. The main focus was on the peak spatial average SAR (psSAR) in the head, which is the relevant quantity for assessing compliance with national and international exposure limits for mobile phones. Morris et al . criticized this paper for not accurately presenting the conclusions of the studies that it reviewed, despite the fact that these conclusions were summarized in this paper by quoting the original authors. However, their critique reflects a simple misreading of our paper and confusion about different metrics of exposure. A second critique, by Gandhi, noted age- and gender-related differences in the absorption of RF energy in the head. We agree with his comments, if they are interpreted as referring to the psSAR in the brain (which is different from the psSAR for the head as a whole and is not used for compliance assessment). This response briefly reviews major factors that limit the relevance of numerical dosimetry/modeling studies under tightly controlled conditions used for compliance assessment to real-world exposures to users of mobile phones.
... The SAR based safety limits, which intend to protect from the thermal MW effects, were developed based on computer simulation of the MW energy absorption in standardized male phantoms. Thus, they do not take into account individual variability in voxel SAR distribution, which may be observed in dependence on polarization, frequency, age, sex, and pregnancy status [1][2][3][4][5][6][7][8]. In addition, the mobile phone SAR values are usually obtained when the phone is positioned about 2 cm from the standard male phantom head, a condition, which is not usually maintained during mobile phone calls. ...
... Very few studies are available on effects of MW-exposure from mobile base stations. Notably, most of them indicate adverse health effects, including cancer, fertility and prenatal development under chronic exposures of humans [1][2][3][4][5][6][7][8][9], mammals [10] and birds [11]. Accumulated dose during chronic exposure seems to be important parameter for assessment of cancer risks from base stations. ...
... This is due to of smaller dimension of child head and consequently thinner pinnae and skulls. Because of this in case of child head, source of electromagnetic radiation is closer to the brain and pituitary gland than in case of adult head.Relevant data shows that the exposure of children is higher than adult exposure 1,2 Because of ethical considerations, human exposure to electromagnetic fields in experimental purposes is limited. Due to this reason is much more convenient to develop a realistic model of the human head by using numerical simulation 3 . ...
... For different frequencies and the corresponding values for the dielectric constant and conductivity of the air and the pituitary gland, the ratio of the normal components of the electric field for these two environments is calculated by using previously formula (2) and results are: In some earlier research, it was found that in the case of rats, which were exposed to mobile phone radiation, that plasma steroid levels in rats are significantly increased. These plasma steroid levels were above certain levels for which thresholds have been reasonably accurately determined. ...
Article
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Background/Aim. This paper investigates the influence of electromagnetic field on the pituitary gland of the child from mobile phone. Electric field distribution in child head and values of Specific Absorption Rate (SAR) at the region of pituitary gland has been determined. This study was performed for the frequencies of 900 MHz, 1800MHz and 2100 MHz, which are most common used in mobile communications. The special attention is dedicated to the values of the electric field and the values of the SAR in the pituitary gland. Methods. In this study for all frequencies the 10g and 1g average SAR have been calculated. In order to obtain the more accurate results for this research 3D realistic model of child head whose size corresponds to an average child (7 years old) had to be created. The electric field distribution and values of average SAR over 10g and 1g trough the model of child head, were obtained by the using numerical calculation based on the Finite Integration Technique (FIT). Results. The results discover where the maximum values of electric field and absorbed energy are, how the field penetrates, and how much the electric field strength decrease with the distance from the radiation source. The largest value of electric field in the region of the pituitary gland is at the frequency of 900MHz. This is a consequence of the highest penetration depth. Lower values of the electric field in the region of the pituitary gland are in case of frequencies 1800MHz and 2100MHz. As the electromagnetic characteristics of tissues depend on the frequency of electromagnetic waves and value for SAR will be different for different tissues and organs. The SAR in the pituitary gland decrease as the frequency increases as a direct consequence of lower penetration depth. Conclusion. The electric field strength from a mobile phone is higher than the value specified by standards for the maximum allowable exposure limits. The high values of electric field are not only in the vicinity of a mobile phone, but also in tissues and organs of the human head. Particular attention should be paid to the exposure of children to radiation of mobile phones. Smaller dimensions of children’s head and smaller thickness of tissues and organs have as a consequence greater penetration of electromagnetic waves.
... Most studies about the impact of electromagnetic radiation from wireless mobile devices focused on the impact of radiation on adult head models [1][2][3][4]. However, recent studies on the impact of electromagnetic radiation from mobile phones on children showed that the radiation exposure of adults differs from that of children and that children are more affected by EMR than adults [5][6][7][8][9][10][11]. A number of studies also showed that electromagnetic radiation causes a higher incidence of malignant brain tumours. ...
... Additionally, The Rulebook on the Limits of Exposure to Non-Ionizing Radiation [15] defines the basic limitations and reference limit levels of exposure of the population to electric, magnetic, and electromagnetic fields of different frequencies that are regarded as safe for human health. The majority of the studies concerning the potential harmful effects of electromagnetic radiation on mobile phones users focused on establishing the electric field values of inside the model body and the SAR (Specific Absorption Rate) values [1][2][3][4][5][6][7][8][9][10]. The magnetic field distribution through the child head model is calculated for the same horizontal crosssection of the model for three different frequencies -0.9 GHz, 1.8 GHz, and 2.1 GHz. ...
Article
Full-text available
Children's everyday use of mobile phones exposes them to significant levels of electromagnetic radiation, causing public concern over the potential adverse effects. This paper discusses the magnetic field distribution from a mobile phone at the frequencies of 0.9, 1.8, and 2.1 GHz through a child head model. Human tissues and organs are represented in terms of their corresponding electromagnetic properties. The results of magnetic field distribution for a horizontal cross-section of the child head model at the three given frequencies are presented in the paper.
... Despite the extensive literature on the subject [8,10,[23][24][25][26], there has been longstanding controversy about whether children absorb more RF energy than adults when using a smartphone [27]. Using realistic virtual human models, it is possible to find any differences in the exposure for different users such as adults vs. children. ...
... Regarding the question about whether children absorb more RF energy than adults when using a smartphone, the debate is still heated in the literature and to date, there are no firm conclusions on this matter [23][24][25][26][27]. The differences in peak local SAR and Sab between adults and children also found in this work are not relevant for compliance assessment [18] but might be important for other purposes, including research on possible biological effects of RF energy. ...
Article
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The recent development of millimeter-wave (mmW) technologies, such as the fifthgeneration (5G) network, comes with concerns related to user exposure. A quite large number of dosimetry studies above 6 GHz have been conducted, with the main purpose being to establish the correlation between different dosimetric parameters and the skin surface temperature elevation. However, the dosimetric studies from 28 GHz user equipment using different voxel models have not been comprehensively discussed yet. In this study, we used the finite-difference time-domain (FDTD) method for the estimation of the absorption of radiofrequency (RF) energy from a microstrip patch antenna array (28 GHz) in different human models. Specifically, we analyzed different exposure conditions simulating three real common scenarios (a phone call scenario, message writing scenario, and browsing scenario) regarding the use of smartphones/tablets by four different individuals (adult male and female, child male and female). From the results of Absorbed Power Density (Sab), it is possible to conclude that all the considered exposure scenarios comply with the safety limits, bothfor adult and children models. However, the high values of the local Specific Absorption Rate (SAR) in the superficial tissues and the slight differences in its distribution between adults and children suggest the need for further and more detailed analysis.
... Assessing RF energy absorption in human phantoms and subsequent SAR estimation remain an established research domain worldwide [12][13][14][15][16][17][18][19][20][21][22][23][24][25]. Dependence of SAR on frequency and polarization of electromagnetic field [12], frequency, power density and time of exposure [13], equivalent dielectric properties of human phantom model [14], distance, frequency and human tissue composition [15], minimum distance from cell tower antennas [16], placement, i.e., height and tilt angle of phone near human torso [17], size of human head during childhood [18], different human organs (like eye, testis, brain, and kidney) [19], electrical properties of human tissue along with surface area [20], different homogeneous models of nine month old infant [21], flat human phantom modelling [22], different multilayer anatomical models, and external field strength [23], etc. have been reported in literature. ...
... Assessing RF energy absorption in human phantoms and subsequent SAR estimation remain an established research domain worldwide [12][13][14][15][16][17][18][19][20][21][22][23][24][25]. Dependence of SAR on frequency and polarization of electromagnetic field [12], frequency, power density and time of exposure [13], equivalent dielectric properties of human phantom model [14], distance, frequency and human tissue composition [15], minimum distance from cell tower antennas [16], placement, i.e., height and tilt angle of phone near human torso [17], size of human head during childhood [18], different human organs (like eye, testis, brain, and kidney) [19], electrical properties of human tissue along with surface area [20], different homogeneous models of nine month old infant [21], flat human phantom modelling [22], different multilayer anatomical models, and external field strength [23], etc. have been reported in literature. Moreover, temperature distributions in human head [24] and eye [25] models have also been reported due to electromagnetic energy absorption. ...
Article
Different global and national electromagnetic regulatory standards have been developed based upon significantly diversified premises, developmental backgrounds, and objectives to safeguard life. Some standards aim at minimizing short duration thermal effects; some try to mitigate non-thermal effects over prolonged duration; and rest have adopted precautionary limits. As a consequence, these global and national electromagnetic standards substantially differ from each other. Moreover, in spite of lossy dielectric nature of plant tissues, electromagnetic energy absorption rate level estimations for a complete plant model have neither been reported in literature nor been considered while preparing safety standards. To this end, Specific Absorption Rate levels have been estimated for a typical Catharanthus roseus plant model — typical geometric shape of the plant prototype has been modelled considering the most practical scenario. Detailed analyses on variation of Specific Absorption Rate levels due to wide discrepancy among the existing electromagnetic regulatory standards have been reported in a quantitative manner. This particular work encompasses dielectric properties measurement of different Catharanthus roseus plant samples, modelling a typical Catharanthus roseus plant containing leaves, flower, and twig with appropriate dielectric properties defined, and finally the simulation-based investigations to estimate the variation in Specific Absorption Rate levels based on the contrasting electromagnetic exposure standards. Specific Absorption Rate levels have been reported at five different telecommunication bands as per two occupational and four public exposure scenarios. Variations among the estimated Specific Absorption Rate levels have been noted to be significant and presented in detail in this article. A total of thirty rigorous simulations have been carried out along with one hundred and twenty Specific Absorption Rate data evaluations to ensure accurate comparison among different electromagnetic standards. Noted vast variations among estimated Specific Absorption Rate levels based on contrasting electromagnetic standards over the frequencies indicate the necessity of re-evaluating all existing guidelines and also call for the need of maintaining a global uniformity among the existing electromagnetic standards worldwide.
... The S-FDTD method has been utilized to assess the impact of uncertainty in bioelectromagnetic applications (including SAR variation), and has shown that the impact of these variations can be significant [7], [12]. Variation in the electrical properties of tissues and shape and size variation between child and adult [13], [14], [16] and also between adults [14], [15] (most importantly the differences in ear thickness [9], [13] from person to person) has been shown to have a significant impact on the SAR in the head. ...
... The S-FDTD method has been utilized to assess the impact of uncertainty in bioelectromagnetic applications (including SAR variation), and has shown that the impact of these variations can be significant [7], [12]. Variation in the electrical properties of tissues and shape and size variation between child and adult [13], [14], [16] and also between adults [14], [15] (most importantly the differences in ear thickness [9], [13] from person to person) has been shown to have a significant impact on the SAR in the head. ...
Article
In this work a novel frequency domain stochastic numerical method named the geometrically stochastic finite difference frequency domain (GS-FDFD) is proposed to study the variation in electromagnetic fields caused by random geometric changes in the model. The delta method approximation is employed to extract the 1-D and 2-D GS-FDFD equations. Two bioelectromagnetic examples are studied. First, a 1-D multi layered body tissue with size variation is analyzed to calculate electromagnetic fields variations. Second, the influence of size variation in a 2-D slice of an anatomical head model on specific absorption rate (SAR) is investigated. In both examples the GS-FDFD results compare well with the benchmark Monte Carlo results.
... More recent studies that examined the impact of electromagnetic radiation from mobile phones on children revealed that there are certain differences compared to radiation exposure of adults, specifically that the impact might be greater in children than in adults [5][6][7][8][9][10][11]. ...
... Most studies that examined the potential adverse effects of electromagnetic radiation from mobile phones on their users were focused on determining the values of electric field inside the model body and the values for SAR (Specific Absorption Rate) [1][2][3][4][5][6][7][8][9][10]. The effects of magnetic field from a mobile phone and its spatial distribution inside the model were seldom considered. ...
... The S-FDTD method has been utilized to assess the impact of uncertainty in bioelectromagnetic applications (including SAR variation), and has shown that the impact of these variations can be significant [7], [12]. Variation in the electrical properties of tissues and shape and size variation between child and adult [13], [14], [16] and also between adults [14], [15] (most importantly the differences in ear thickness [9], [13] from person to person) has been shown to have a significant impact on the SAR in the head. ...
... The S-FDTD method has been utilized to assess the impact of uncertainty in bioelectromagnetic applications (including SAR variation), and has shown that the impact of these variations can be significant [7], [12]. Variation in the electrical properties of tissues and shape and size variation between child and adult [13], [14], [16] and also between adults [14], [15] (most importantly the differences in ear thickness [9], [13] from person to person) has been shown to have a significant impact on the SAR in the head. ...
Article
DOWNLOAD LINK: https://utah.instructure.com/courses/558911/files/90896623/download?wrap=1 This paper presents a stochastic scheme called geometrically stochastic FDTD (GS-FDTD) to insert the statistical variation of model geometry directly into the finite difference time domain (FDTD) method. Both 1D and 2D GS-FDTD formulations are presented. The method is utilized to investigate the impact of tissue size variation on the calculated EM fields in 1D and 2D layered and cylindrical biological models. In addition, we assess the SAR variance in a 2D slice of a human head model at 835 MHz with the size of the outer layer consisting of skin, ear and nose varying ±10 percent. Also an improved method of calculating specific absorption rate (SAR) variance is presented. Results are verified using the Monte Carlo technique.
... (Gandhi and Kang 2004;Gandhi et al. 1996) was primarily due to the thinner ears of children, which brought the physical location of the phone closer to the head. (Gandhi 2015) Since the phone is in the very-near-field wherein the fields decrease as the cube of the distance, even a very small difference in distance can result in a significantly higher exposure. Significant differences in SAR were observed when this effect was considered, (Gandhi and Kang 2004;Gandhi et al. 2012) but minimal differences were observed in models without an ear, or without considering the effect of the smaller pinnae of the ear. ...
Chapter
Bioelectromagnetic dosimetry is used to determine the electromagnetic fields in a biological body (human, animal, or experimental phantom) from devices that are far from the body (plane-wave exposures), near the body (near-field exposures), or inside the body (implantable medical devices). From simplified models (spheres, cylinders, layered planes) representing the human body, advances in commercially available radiofrequency devices (cell phones, in particular) and the availability of ever-more computing power have led to the development of detailed simulations based on anatomical millimeter-resolution models. Dosimetry adds to our overall understanding of how electromagnetic fields interact with the body and how to design devices that take advantage of these interactions. Opportunities for progress in dosimetry will follow new device designs and applications, integrating advanced multiphysics simulations for design and optimization with rapid prototyping and test equipment.
... In the past, exposure assessments in human heads were studied and analyzed using different adult and children head models [7] - [21]. According to those studies, the EM radiation levels in children are similar [21] or higher [5], [12] - [20] than those for adults. ...
Article
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Given the rapid introduction of mobile phones and other portable wireless devices into society, and the increased possibility of young children using or being exposed to electromagnetic (EM) fields, a study of specific absorption rate (SAR) in the head of young children is becoming increasingly relevant. To accurately evaluate the exposure of children to electromagnetic fields, realistic head models, which consider the age-specific anatomical structure and age-dependent tissues dielectric properties, are developed. During postnatal development of human tissues, the number and size of cells increase while the proportion of water content decreases. Such changes result generally in significant changes in the dielectric properties of tissues. The SAR levels for different ages are investigated using the developed child’s head models when young children or their parents use a standard mobile phone. The results show that the maximum SAR levels in brain tissues of young children (3 months) are higher by up to 61% and 78% than adults at the lowest (700 MHz) and highest (2600 MHz) investigated frequencies, respectively. The percentage absorption power in the heads of young children (3 months) is higher by up to 40.6% and 24% than the values for adults at 700 MHz and 2600 MHz, respectively. Our investigation shows that previous studies, which used scaled head models without considering the age-dependent variations in the head anatomy and/or age-dependent tissues’ dielectric properties, underestimated SAR levels in the children’s heads. The obtained results using the developed realistic head models indicate that for young children, a lower limit on radiated power might be required to meet the acceptable dosimetry levels.
... According to some authors, higher SAR values in the child head are due to thinner earlobes and therefore due to the position of the antenna, which is closer to the head. Likewise, with reduction of the thickness of earlobes, the absorption of RF energy in the surface tissues reduces and the value of SAR in the deeper tissues potentially increases [10,11]. However, the true-to-life degree of the model and the source of electromagnetic radiation vary from one research to another. ...
Article
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Daily use of wireless devices, especially mobile phones, has caused great concern among the public about the possible health effects of electromagnetic radiation to which the users of these devices, primarily children, are exposed. This paper summarizes the habit of using mobile phones by children and teenagers and its connection with possible harmful biological effects of electromagnetic radiation of these devices. This paper describes the procedure of creating models of adult and child heads that are used for numerical calculation of electromagnetic field penetration and the absorbed energy. As we know, the human body consists of many different tissues and organs, so each of them needs to be described by the appropriate electromagnetic characteristics. Key words: mobile phone, electromagnetic characteristics of tissues, model of child head, specific absorption rate
... Foster and Chou [3] argue that children have the same exposure to the brain as adults, and face equal risks, based on their review of studies comparing the intracranial dose rates of absorbed RF-EMR in adults and children. Others, for example Gandhi [4], contend that children have proportionally greater intracranial peak tissue dose given their thinner skulls and the higher water content of their cerebral tissues. Moreover, the rapid rate of growth and development, and incomplete myelination of the brain, make children uniquely susceptible to the effects of radiation [5], [6]. ...
Article
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The greater vulnerability of children to the effects of environmental hazards has raised concerns about their exposure to and the resultant absorption of mobile phone radiation. Foster and Chou (2014) reviewed published studies that used computer models of radio-frequency electromagnetic fields to estimate and compare the tissue dose rate in the heads of children and adults using mobile phones. Their review confuses exposure with absorption, and the study results conclude erroneously that children are not more exposed than adults. We show that their review was not executed systematically. There are discrepancies between text summaries and the graphed ratios of child: adult peak special specific absorption rate, in line with the author's hypothesis that children have the same or lower tissue dose than adults. Even the underlying precept of their review is flawed, as the results of deterministic models are treated as random variables. In fact, model results are entirely determined by the underlying assumptions and the structure of the model. Models are included in their unsystematic review that do not consider differences in dielectric constants among different tissues, or across ages, while other models that consider such differences are not included. In this paper, we discuss the differences between exposure and tissue absorption and re-examine the results presented by Foster and Chou. Based upon our review, we suggest an alternative interpretation of the published literature. In an Appendix, we discuss modeling of tissue dose in the context of governmental safety certification processes.
... Some authors [10, 12] see the problem as not only due to the difference in energy absorption, but also because children are still developing and so must be considered more sensitive [13]. However, whether children absorb larger quantities of energy from mobile devices due to different anatomical and physiological characteristics compared to adults is debatable [10,12,[14][15][16][17][18][19]. ...
Article
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Background For more than 20 years, the potential health risks of radiofrequency electromagnetic field (RF EMF) exposure from mobile communication devices on children and adolescents have been examined because they are considered sensitive population groups; however, it remains unclear whether such exposure poses any particular risk to them. Objectives The aim of this review was to systematically analyze and evaluate the physiological and health-related effects of RF EMF exposures from wireless communication devices (mobile phones, cordless phones, Bluetooth, etc.) on children and adolescents. Methods This review was prepared according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Methodological limitations in individual studies were assessed using the Office of Health Assessment and Translation (OHAT) Risk-of-Bias Rating Tool for Human and Animal Studies. Results A total of 42 epidemiological and 11 experimental studies were eligible for this review. Most of the studies displayed several methodological weaknesses that limited the internal validity of the results. Due to a lack of consistency regarding the outcomes as well as the lack of scientific rigor in most reviewed studies, the body of evidence for the effects of RF EMF of mobile communication devices on subjective symptoms, cognition, and behavior in children and adolescents was low to inadequate. Evidence from the studies investigating early childhood development, brain activity, cancer, and physiological parameters was considered inadequate for drawing conclusions about possible effects. Discussion Overall, the body of evidence allows no final conclusion on the question whether exposure to RF EMF from mobile communication devices poses a particular risk to children and adolescents. There has been rapid development in technologies generating RF EMF, which are extensively used by children and adolescents. Therefore, we strongly recommend high-quality systematic research on children and adolescents, since they are generally considered as sensitive age groups.
... For electromagnetic sources that are in or very near the body (medical implants, cell phones, wearables, etc.) the exact placement and orientation of the source significantly impacts the field distribution [239], [173]. Near-field sources such as cell phones, medical implants, etc., require great precision in their modeling. ...
Article
Rapid advances in antennas, propagation, electromagnetics, and materials are opening new and unexplored opportunities in body area sensing and stimulation. Next-generation wearables and implants are seamlessly providing round-the-clock monitoring. In turn, numerous applications are brought forward with the potential to ultimately transform healthcare, sports, consumer electronics, and beyond. This review paper provides a comprehensive overview, discusses challenges and opportunities, and indicates future directions for: (a) enabling technologies needed to make body area sensing and stimulation a reality, and (b) emerging bioelectromagnetics applications that may readily benefit from such technologies.
... It seems that the increase in power absorption from a mobile phone is inversely proportional to the child's age due to differences such as a lower thickness of pinna, skin, and skull of the younger child models. It is indicated that, in general, children are more vulnerable to electromagnetic radiation than adults [21][22][23]. ...
Article
A detailed dosimetry study of electromagnetic absorption and temperature rise under real scenarios is delivered when a mobile phone is used inside an elevator cabin. Numerically accurate human models of a 7 th month pregnant woman and a 5-year-old female child are utilized as the exposed subjects. The female child acts as the phone user. The mobile phone is modeled in three talk positions (parallel, tilt, and cheek) operating at 1000 MHz and 1800 MHz. From the obtained numerical results for the specific absorption rate (SAR) and temperature rise induced by the mobile radiofrequency (RF) radiation, it is found that the child's RF exposure is significantly affected by the phone position and less affected by the relevant position of the human models. The exact opposite case applies for the pregnant woman model and its fetus. Almost all numerical investigations are carried out inside a metallic elevator cabin.
... There is limited information on RF-EMF exposure levels among children and their relevant environments such as kindergartens and schools. 20,21 Some studies have estimated that absorption of RF-EMF from both near- 22,23 and far-field 24 sources is greater in children than adults. Age could be one of the parameters to influence differential biological effects of RF-EMF exposures. ...
Article
Full-text available
The aim of this study was to assess environmental and personal radiofrequency-electromagnetic field (RF-EMF) exposures in kindergarten children. Ten children and 20 kindergartens in Melbourne, Australia participated in personal and environmental exposure measurements, respectively. Order statistics of RF-EMF exposures were computed for 16 frequency bands between 88 MHz and 5.8 GHz. Of the 16 bands, the three highest sources of environmental RF-EMF exposures were: Global System for Mobile Communications (GSM) 900 MHz downlink (82 mV/m); Universal Mobile Telecommunications System (UMTS) 2100MHz downlink (51 mV/m); and GSM 900 MHz uplink (45 mV/m). Similarly, the three highest personal exposure sources were: GSM 900 MHz downlink (50 mV/m); UMTS 2100 MHz downlink, GSM 900 MHz uplink and GSM 1800 MHz downlink (20 mV/m); and Frequency Modulation radio, Wi-Fi 2.4 GHz and Digital Video Broadcasting-Terrestrial (10 mV/m). The median environmental exposures were: 179 mV/m (total all bands), 123 mV/m (total mobile phone base station downlinks), 46 mV/m (total mobile phone base station uplinks), and 16 mV/m (Wi-Fi 2.4 GHz). Similarly, the median personal exposures were: 81 mV/m (total all bands), 62 mV/m (total mobile phone base station downlinks), 21 mV/m (total mobile phone base station uplinks), and 9 mV/m (Wi-Fi 2.4 GHz). The measurements showed that environmental RF-EMF exposure levels exceeded the personal RF-EMF exposure levels at kindergartens.Journal of Exposure Science and Environmental Epidemiology advance online publication, 19 October 2016; doi:10.1038/jes.2016.55.
Conference Paper
Specific absorption rate (SAR) simulation may be used to assess exposure levels, health risk and compliance with recommendations of wireless devices EMF exposure limits. When developing a numerical model of a human head the segmentation system decides the boundary between the modeled tissues. E.g., using different strategies (thresholds or parameters) some tissues may be modeled thinner or thicker. The objective of this work is to investigate the sensitivity of the skull thickness in the SAR. Starting with a single DICOM study, two models differing only in the skull thickness were developed. The bones mass of one of the models were 35% lighter than the other's. Under the same exposure conditions, the 1g-psSAR in the brain of the “thin skull” model was 5% higher than the 1g-psSAR of the “thick skull” model. This difference applies to the particular conditions of the performed simulations, then we can conclude that the expected uncertainty related to the skull modelling is of this order of value. We also can expect higher SAR differences corresponding to age related skull thickness differences between children and adults.
Article
This paper represents the numerical analysis of Specific Absorption Rate (SAR) and temperature distribution within a real child head model exposed to mobile phone radiation at the frequency of f = 900 MHz. In this research the SAR and temperature distribution are obtained by numerical solutions of the equation of electromagnetic waves propagation and by bioheat equation, respectively, and are shown inside different biological tissues and organs during exposure to electromagnetic radiation from a mobile phone. As electromagnetic properties of tissues depend on the electromagnetic waves frequency, the value of SAR and temperature will be different for different tissues and organs. The maximum absorption of electromagnetic energy is in the surface layers of the model, whereby this value is greater than the maximum allowed value defined by standards. Furthermore, the increase in temperature is the highest in those biological tissues and organs that are closest to the source of radiation i.e. a mobile phone. Moving away from a mobile phone, the temperature decreases, but more slowly than the SAR values. In the analysis of the temperature rise resulting from tissues and organs heating due to the effects of electromagnetic fields on a child’s head, special attention will be given to the maximum temperature increase in the brain.
Chapter
This chapter summarizes some of the controversies in recent decades regarding non-ionizing radiation (NIR). A number of studies investigated the possibilities of apparent cancer “clusters” being linked to Radiofrequency (RF) exposure. Among early controversies, increased risk of childhood leukemia associated with radio transmitters in Hawaii and within a 6 km radius of the Vatican City Radio transmitter rank among the more prominent. During the late 1990s, there was much more controversy about mobile phone base station siting than about cancer being caused by mobile phone exposure. The use of lasers in outdoor and indoor entertainment also can represent a hazard if not installed or controlled adequately. International exposure guidelines have been developed to provide protection against established effects from NIR by various scientific organizations. In order to prevent or reduce possible risks related to NIR exposure, some national governments or local authorities have adopted measures that replace or complement science-based exposure limits.
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Electromagnetic simulation based channel modeling is presently considered as a promising option for wireless body area network (WBAN) channel modeling. The benefits of simulation-based channel modeling are obvious: realistic channel characteristics for required environments and situations are provided flexibly and cheaply. Additionally, the use of simulation based channel modeling may overcome several challenges related to the use of measurement data, such as uncertainties and inaccuracies due to cabling, unintentional changes in the position of the test person or the antennas, etc. There are several numerical methods suitable for simulation based channel modeling, both full-wave and an asymptotic solutions. The choice of the numerical approach depends on the nature of the communication links of the wireless body network being considered. This paper presents a general overview, including recent progress, of the electromagnetic simulation based WBAN channel modeling techniques. Advantages, disadvantages and the most appropriate applications are described. Furthermore, the features of the different techniques are compared.
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The exposure ratio of multiple micro-power devices is difficult to be evaluated in terms of the choices of measure point and public exposure control limit due to various frequencies, antenna transmit powers and device topologies, whereas the traditional multi-device evaluation method were found unable to achieve consistent and rational results. In order to address these challenges, a combined radiation device mode is introduced to simplify the choice of measure point, and a convert algorithm is proposed to determine public exposure control limit in any distance. The adjusting factors are added to the convert algorithm to improve its position consistency and limit rationality, and a neural network is designed to optimize its nonlinear coefficients. Finally, the radiation pressure tests in lineal and rectangular topologies are provided to corroborate our studies.
Conference Paper
In this paper, the study is centered on the various effects of Electromagnetic Field (EMF) on the health of habitats living near a mobile tower. The proposed study has been focused on the particular tower of the State-owned mobile operator "BSNL" i.e., Bharat Sanchar Nigam Limited. It is located in the surrounding areas of Village Murthal (Sonipat). The aim of this investigation is to identify the vulnerable power of EMF Radiations at the particular location around the tower and compare them with the standard prescribed by the Department of Telecommunication (DoT).
Article
Electromagnetic regulatory guidelines prescribed by the international and national organizations are in effect worldwide to protect humans from immediate health effects. For restricting human exposure to electromagnetic radiation in near field, a quantitative term ‘specific absorption rate (SAR) limit’ has been coined and well established in literature. In addition, reference power density limit has also been prescribed in far field for human safety. At the same time, plants and fruits also absorb reasonable amount of electromagnetic energy due to high permittivity and electrical conductivity. Unfortunately, there is not much concern regarding electromagnetic energy absorption in plants and fruits, and no prescribed SAR limit in spite of recent reports in literature. Unlike humans, plants and fruits are of asymmetric shapes and sizes; therefore even at a particular frequency and fixed reference power density, electromagnetic energy absorption rate i.e., SAR in plants and fruits is expected to differ depending upon angle of incidence and wave polarization. To address these issues in detail, a typical bunch of three single layered water apples has been prototyped and exposed to plane wave irradiation at five different frequency bands as per the existing Indian electromagnetic regulatory guidelines. Broadband dielectric properties of water apples have been measured using open ended coaxial probe technique; thereafter, measured dielectric properties have been fed into the designed model. At a particular frequency, reasonable variations in magnitude and position of maximum local point (MLP) SAR, 1 g averaged SAR, and 10 g averaged SAR data have been noted for six different combinations of angle of incidence and wave polarization. This whole course of action is repeated over five different frequency bands. Moreover, variations in observed SAR data are also compared with previously reported variations in SAR data for a multilayer fruit structure. Observations indicate different order of changes in SAR for different fruit structures due to similar combinations of frequency, power density, angle of incidence, and wave polarization. Hence, direct definition of SAR limits for plant and fruit structures should be adopted even in far field in conjunction with reference power density.
Article
Purpose The purpose of this paper is to determine the impact of human age on the distribution of electric field and absorbed energy that originates from a mobile phone. Design/methodology/approach This research was performed for frequencies of 900, 1800 and 2100 MHz, which are used in a mobile communication system. To obtain the most accurate results, 3 D realistic model of the child’s head has been created whereby the dimensions of this model correspond to the dimensions of a seven-year-old child. Distribution of the electric field and specific absorption rate (SAR) through the child’s head was obtained by numerical analysis based on the finite integration technique. Findings The results discover that amount of absorbed energy is greater in the surface layers of the child’s head model when the electromagnetic (EM) characteristics of tissues are adjusted for the child. This deviation corresponds to different EM characteristics of biological tissues and organs of an adult person compared to a child. Research limitations/implications The study deals with penetrated electrical field and absorbed EM field energy. There is space for further studies of other EM field effects (e.g. thermal effects). Practical implications The analysis of obtained results leads to idea that mobile phones and devices aimed for children using should be modified to provide SAR values inside prescribed standards. Social implications The obtained results are foundation for future research on influence of EM fields of mobile devices on human health. Originality/value The proposed procedure offers the model for accurate estimation and quality analysis of SAR and EM field distribution inside child head tissue.
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The peak spatial specific absorption rate (SAR) assessed with the standardized specific anthropometric mannequin head phantom has been shown to yield a conservative exposure estimate for both adults and children using mobile phones. There are, however, questions remaining concerning the impact of age-dependent dielectric tissue properties and age-dependent proportions of the skull, face and ear on the global and local absorption, in particular in the brain tissues. In this study, we compare the absorption in various parts of the cortex for different magnetic resonance imaging-based head phantoms of adults and children exposed to different models of mobile phones. The results show that the locally induced fields in children can be significantly higher (>3 dB) in subregions of the brain (cortex, hippocampus and hypothalamus) and the eye due to the closer proximity of the phone to these tissues. The increase is even larger for bone marrow (>10 dB) as a result of its significantly high conductivity. Tissues such as the pineal gland show no increase since their distances to the phone are not a function of age. This study, however, confirms previous findings saying that there are no age-dependent changes of the peak spatial SAR when averaged over the entire head.
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This paper compares the maximum allowable powers of some typical cellular telephones at 835 and 1900 MHz for compliance with the limits of specific absorption rates (SAR) given in ANSI/IEEE, ICNIRP and the proposed modification of ANSI/IEEE safety guidelines. It is shown that the present ANSI/IEEE guideline is the most conservative with the ICNIRP guidelines allowing a maximum radiated powerthat is 2.5-3 times higher, and the proposed IEEE modification of treating pinna as an extremity tissue the least conservative allowing even higher radiated powers by up to 50%. The paper also expands the previously reported study of energy deposition in models of adults versus children to two different and distinct anatomically-based models of the adult head, namely the Utah model and the 'Visible Man' model, each of which is increased or reduced by the voxel size to obtain additional head models larger or smaller in all dimensions by 11.1% or -9.1%, respectively. The peak 1 g body-tissue SAR calculated using the widely accepted FDTD method for smaller models is up to 56% higher at 1900 MHz and up to 20% higher at 835 MHz compared to the larger models, with the average models giving intermediate SARs. Also given in the paper is a comparison of the peak 1 g and 10 g SARs for two different anatomically-based models with 6 mm thick smooth plastic ear models used for SAR compliance testing. The SARs obtained with the insulating plastic ear models are up to two or more times smaller than realistic anatomic models. We propose a 2 mm thin shell phantom with lossy ear that should give SARs within +/- 15% of those of anatomic models.
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Increasingly, mobile telephones are becoming pocket-sized and are being left in the shirt pocket with a connection to the ear for hands-free operation. We have considered an anatomic model of the chest and a planar phantom recommended by US FCC to compare the peak 1 and 10 g SARs for four typical cellular telephones, two each at 835 and 1900 MHz. An agreement within +/- 10% is obtained between calculated and experimental 1 and 10 g SARs for various separations (2-8 mm) from the planar phantom used to represent different thicknesses of the clothing both for the antenna away from or turned back towards the body. Because of the closer placement of the antennas relative to the body, the peak 1 and 10 g SARs are considerably higher (by a factor of 2-7) for pocket-mounted telephones as compared to the SARs obtained using a 6 mm thick plastic ear head model--a procedure presently accepted both in the US and Europe. This implies that a telephone tested for SAR compliance against the model of the head may be severely out of compliance if it were placed in the shirt pocket.
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A 2-mm-thick plastic shell with 5-10-mm-thick tapered plastic spacer in the shape of a "pinna"-specific anthropomorphic mannequin (SAM) head model is being used for determination of the specific absorption rate (SAR) of cellular telephones for compliance testing against IEEE and the International Commission on Non-Ionizing Radiation Protection (ICNIRP) Safety Guidelines used in the U.S. and Europe, respectively. We have used three-dimensional computer-aided design files of the SAM Model with 1-mm resolution to calculate peak 1- and 10-g SAR for "cheek" and "15°-tilted" positions of some typical telephones for comparison with those for three anatomic models of the head to show that the SAR obtained for SAM is up to two or more times smaller than for anatomic models. This is due to the shift of the high SAR locations to a low radiated fields region away from the antenna, particularly at 835 MHz, and a substantial physical separation from the absorptive phantom at 1900 MHz. Due to the use of lossless plastic for the "pinna," another handicap of the SAM model is the total lack of knowledge of 1- or 10-g SAR in the pinna tissues required by all safety guidelines (current or proposed). To remedy this situation, we propose a modified SAM with a lossy "pinna," for which 1- and 10-g SARs are relatively close to those for anatomic models, provided we use a fluid of higher conductivity than that currently used for compliance testing at 835 MHz. Lastly, we compare the implications of the current IEEE and ICNIRP guidelines and the newly proposed IEEE guidelines with a relaxed limit of 4.0 W/kg for any 10-g of tissue of the pinna for maximum allowable powers for cellular telephones at 835 and 1900 MHz to show that the newly proposed relaxed IEEE limits will allow radiated powers that may be 8-16 times those permitted by the current IEEE Standard and up to two times higher than those permitted under ICNIRP guidelines used in over 30 countries.
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The authors have used the finite-difference time-domain method and a new millimeter-resolution anatomically based model of the human to study electromagnetic energy coupled to the head due to mobile telephones at 835 and 1900 MHz. Assuming reduced dimensions characteristic of today's mobile telephones, the authors have obtained SAR distributions for two different lengths of monopole antennas of lengths λ/4 and 3λ/8 for a model of the adult male and reduced-scale models of 10- and 5-year-old children and find that peak one-voxel and 1-g SARs are larger for the smaller models of children, particularly at 835 MHz. Also, a larger in-depth penetration of absorbed energy for these smaller models is obtained. The authors have also studied the effect of using the widely disparate tissue properties reported in the literature and of using homogeneous instead of the anatomically realistic heterogeneous models on the SAR distributions. Homogeneous models are shown to grossly overestimate both the peak 1-voxel and 1-g SARs. Last, the authors show that it is possible to use truncated one-half or one-third models of the human head with negligible errors in the calculated SAR distributions. This simplification will allow considerable savings in computer memory and computation times
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There has been long-standing controversy, both among scientists and in the public, about whether children absorb more radio frequency (RF) energy in their heads than adults when using a mobile telephone. This review summarizes the current understanding of this issue, and some of the complexities in comparing the absorption of RF energy in different individuals from use of mobile phones. The discussion is limited to dosimetric issues, i.e., possible age-related differences in absorption of RF energy in the heads of mobile phone users. For most metrics of exposure, in particular those relevant to assessing the compliance of handsets with regulatory limits, there is no clear evidence for age-related differences in exposure. For two metrics of exposure, there is a clear evidence that age can play a factor: 1) the local specific absorption rate (SAR), in particular anatomically defined locations within the brain, will vary with head size and hence with age and 2) the SAR, in particular tissues, (e.g., bone marrow in the skull) can vary with age due to age-related differences in the dielectric properties of tissue. However, these differences involve SAR levels that are below the 1-g or 10-g peak spatial SAR (psSAR averaged over 1 or 10 g of tissue) and have no significance for compliance assessment. Age-related differences observed in worst case simulations such as presently considered are difficult to generalize to human populations under real-world exposure conditions due to many variables that determine SAR during realistic usages.
Article
The steady increase of mobile phone usage, especially mobile phones by children, has led to a rising concern about the possible adverse health effects of radio frequency electromagnetic field exposure. The objective of this work is to study whether there is a larger radio frequency energy absorption in the brain of a child compared to that of an adult. For this reason, three high-resolution models, two child head models (6 - and 11-year old) and one adult head model (34-year old) have been used in the study. A finite-difference time-domain method was employed to calculate the specific absorption rate (SAR) in the models from exposure to a generic handset at 1750 MHz. The results show that the SAR distributions in the human brain are age-dependent, and there is a deeper penetration of the absorbed SAR in the child’s brain. The induced SAR can be significantly higher in subregions of the child’s brain. In all of the examined cases, the SAR values in the brains of a child and an adult are well below the IEEE safety standard.
Article
The existing cell phone certification process uses a plastic model of the head called the Specific Anthropomorphic Mannequin (SAM), representing the top 10% of U.S. military recruits in 1989 and greatly underestimating the Specific Absorption Rate (SAR) for typical mobile phone users, especially children. A superior computer simulation certification process has been approved by the Federal Communications Commission (FCC) but is not employed to certify cell phones. In the United States, the FCC determines maximum allowed exposures. Many countries, especially European Union members, use the "guidelines" of International Commission on Non-Ionizing Radiation Protection (ICNIRP), a non governmental agency. Radiofrequency (RF) exposure to a head smaller than SAM will absorb a relatively higher SAR. Also, SAM uses a fluid having the average electrical properties of the head that cannot indicate differential absorption of specific brain tissue, nor absorption in children or smaller adults. The SAR for a 10-year old is up to 153% higher than the SAR for the SAM model. When electrical properties are considered, a child's head's absorption can be over two times greater, and absorption of the skull's bone marrow can be ten times greater than adults. Therefore, a new certification process is needed that incorporates different modes of use, head sizes, and tissue properties. Anatomically based models should be employed in revising safety standards for these ubiquitous modern devices and standards should be set by accountable, independent groups.
Article
This paper reviews and summarises the state of knowledge on dielectric properties of tissues; in particular those obtained as a function of age. It also examines the impact of variation in dielectric data on the outcome of recent dosimetric studies assessing the exposure of children to electromagnetic fields.
Article
The electromagnetic exposure of cell phone users depends on several parameters. One of the most dominant of these is the distance between the cell phone and the head tissue. The pinna can be regarded as a spacer between the top of the phone and the head tissue. The size of this spacer has not yet been systematically studied. The objective of this article is to investigate the variations of distance as a function of age of the exposed person, and the mechanical force on the pinna and how it affects the peak spatial specific absorption rate (psSAR). The distances were measured for adults and children (6-8 years of age) while applying a well-defined force on the pinna using a custom-developed measurement device. The average distances of the pinnae to the heads and their standard deviations showed no major differences between the two age groups: 10.5 +/- 2.0 mm for children (6-8 years) and 9.5 +/- 2.0 mm for adults. The pinnae of our anatomical high-resolution head models of one adult and two children were transformed according to the measurement results. The numerical exposure analysis showed that the reduced distance due to the pinna compression can increase the maximum 10 g psSAR by approximately 2 dB for adults and children, if the exposure maximum is associated with the upper part of the phone.
Article
The dielectric properties of ten rat tissues at six different ages were measured at 37 degrees C in the frequency range of 130 MHz to 10 GHz using an open-ended coaxial probe and a computer controlled network analyser. The results show a general decrease of the dielectric properties with age. The trend is more apparent for brain, skull and skin tissues and less noticeable for abdominal tissues. The variation in the dielectric properties with age is due to the changes in the water content and the organic composition of tissues. The percentage decrease in the dielectric properties of certain tissues in the 30 to 70 day old rats at cellular phone frequencies have been tabulated. These data provide an important input in the provision of rigorous dosimetry in lifetime-exposure animal experiments. The results provide some insight into possible differences in the assessment of exposure for children and adults.
Article
This study analyzes the main parameters that should influence the specific absorption rate (SAR) in children's heads. The evolution of their head shape and the growth of specific parameters, such as the skull thickness, are analyzed. The influence of these parameters on the radio frequency (RF) exposure of children's head is studied. The SAR over 1 g in specific tissue is assessed in different children's head models based on magnetic resonance imaging (MRI) and on non-uniformly down-scaled adult heads. Comparisons with SAR data in adults are reported using a handset with a patch antenna operating at 900 MHz.
Article
The increasing use of mobile communication devices, especially mobile phones by children, has triggered discussions on whether there is a larger radio frequency (RF) energy absorption in the heads of children compared to that of adults. The objective of this study was to clarify possible differences in RF energy absorption in the head region of children and adults using computational techniques. Using the finite-difference time-domain (FDTD) computational method, a set of specific absorption rate (SAR) calculations were performed for anatomically correct adult and child head models. A half-wave dipole was used as an exposure source at 900, 1800 and 2450 MHz frequencies. The ear and eye regions were studied representing realistic exposure scenarios to current and upcoming mobile wireless communication devices. The differences in absorption were compared with the maximum energy absorption of the head model. Four magnetic resonance imaging (MRI) based head models, one female, one adult, two child head models, aged 3 and 7 years, were used. The head models greatly differ from each other in terms of size, external shape and the internal anatomy. The same tissue dielectric parameters were applied for all models. The analyses suggest that the SAR difference between adults and children is more likely caused by the general differences in the head anatomy and geometry of the individuals rather than age. It seems that the external shape of the head and the distribution of different tissues within the head play a significant role in the RF energy absorption.
Article
The Specific Absorption Rate (SAR) produced by mobile phones in the head of adults and children is simulated using an algorithm based on the Finite Difference Time Domain (FDTD) method. Realistic models of the child and adult head are used. The electromagnetic parameters are fitted to these models. Comparison also are made with the SAR calculated in the children model when using adult human electromagnetic parameters values. Microstrip (or patch) antennas and quarter wavelength monopole antennas are used in the simulations. The frequencies used to feed the antennas are 1850 MHz and 850 MHz. The SAR results are compared with the available international recommendations. It is shown that under similar conditions, the 1g-SAR calculated for children is higher than that for the adults. When using the 10-year old child model, SAR values higher than 60% than those for adults are obtained.