Masao Taki

Publications of Masao Taki

• Analysis of three-dimensional SAR distributions emitted by mobile phones in an epidemiological perspective.

  Authors: Isabelle Deltour, Joe Wiart, Masao Taki, Kanako Wake, Nadège Varsier, Simon Mann, Joachim Schüz, Elisabeth Cardis

  Bioelectromagnetics. 06/2011; 32(8):634-43.

  The three-dimensional distribution of the specific absorption rate of energy (SAR) in phantom models was analysed to detect clusters of mobile phones producing similar spatial deposition of energy inThe three-dimensional distribution of the specific absorption rate of energy (SAR) in phantom models was analysed to detect clusters of mobile phones producing similar spatial deposition of energy in the head. The clusters' characteristics were described from the phones external features, frequency band and communication protocol. Compliance measurements with phones in cheek and tilt positions, and on the left and right side of a physical phantom were used. Phones used the Personal Digital Cellular (PDC), Code division multiple access One (CdmaOne), Global System for Mobile Communications (GSM) and Nordic Mobile Telephony (NMT) communication systems, in the 800, 900, 1500 and 1800 MHz bands. Each phone's measurements were summarised by the half-ellipsoid in which the SAR values were above half the maximum value. Cluster analysis used the Partitioning Around Medoids algorithm. The dissimilarity measure was based on the overlap of the ellipsoids, and the Manhattan distance was used for robustness analysis. Within the 800 MHz frequency band, and in part within the 900 MHz and the 1800 MHz frequency bands, weak clustering was obtained for the handset shape (bar phone, flip with top and flip with central antennas), but only in specific positions (tilt or cheek). On measurements of 120 phones, the three-dimensional distribution of SAR in phantom models did not appear to be related to particular external phone characteristics or measurement characteristics, which could be used for refining the assessment of exposure to radiofrequency energy within the brain in epidemiological studies such as the Interphone.

• Analysis of gene expression in a human-derived glial cell line exposed to 2.45 GHz continuous radiofrequency electromagnetic fields.

  Authors: Tomonori Sakurai, Tomoko Kiyokawa, Eijiro Narita, Yukihisa Suzuki, Masao Taki, Junji Miyakoshi

  Journal of radiation research. 02/2011; 52(2):185-92.

  The increasing use of mobile phones has aroused public concern regarding the potential health risks of radiofrequency (RF) fields. We investigated the effects of exposure to RF fields (2.45 GHz,The increasing use of mobile phones has aroused public concern regarding the potential health risks of radiofrequency (RF) fields. We investigated the effects of exposure to RF fields (2.45 GHz, continuous wave) at specific absorption rate (SAR) of 1, 5, and 10 W/kg for 1, 4, and 24 h on gene expression in a normal human glial cell line, SVGp12, using DNA microarray. Microarray analysis revealed 23 assigned gene spots and 5 non-assigned gene spots as prospective altered gene spots. Twenty-two genes out of the 23 assigned gene spots were further analyzed by reverse transcription-polymerase chain reaction to validate the results of microarray, and no significant alterations in gene expression were observed. Under the experimental conditions used in this study, we found no evidence that exposure to RF fields affected gene expression in SVGp12 cells.

• Short-term exposure to a 1439-MHz TDMA signal exerts no estrogenic effect in rats.

  Authors: Hiroharu Yamashita, Keisuke Hata, Hironori Yamaguchi, Giichiro Tsurita, Kanako Wake, Soichi Watanabe, Masao Taki, Shoogo Ueno, Hirokazu Nagawa

  Bioelectromagnetics. 10/2010; 31(7):573-5.

  The aim of this study was to elucidate the possible effects of short-term exposure to a 1439-MHz electromagnetic field (EMF) employing time division multiple access (TDMA), which is the basis of theThe aim of this study was to elucidate the possible effects of short-term exposure to a 1439-MHz electromagnetic field (EMF) employing time division multiple access (TDMA), which is the basis of the Japanese Personal Digital Cellular system, on estrogenic activity in rats. Sixty-four ovariectomized female Sprague-Dawley rats were divided into four groups: EMF exposure (EM), sham exposure, cage control, and 17 beta-estradiol injected (E2). The EM group was exposed, for 4 h per day on three consecutive days, to the 1439-MHz TDMA signal that produced 5.5-6.1 and 0.88-0.99 W/kg average specific absorption rates in the brain and the whole body, respectively. The uterine wet mass and serum estradiol level significantly increased in the E2 group, while there were no differences among the other three groups. Although negative effects of long-term EMF exposure must be thoroughly investigated before a final conclusion can be reached, our results do not support the assumption that the high frequency EMF used in cellular phones exerts estrogenic activity.

• The estimation of 3D SAR distributions in the human head from mobile phone compliance testing data for epidemiological studies.

  Authors: Kanako Wake, Nadège Varsier, Soichi Watanabe, Masao Taki, Joe Wiart, Simon Mann, Isabelle Deltour, Elisabeth Cardis

  Physics in medicine and biology. 10/2009; 54(19):5695-5706.

  A worldwide epidemiological study called 'INTERPHONE' has been conducted to estimate the hypothetical relationship between brain tumors and mobile phone use. In this study, we proposed a method toA worldwide epidemiological study called 'INTERPHONE' has been conducted to estimate the hypothetical relationship between brain tumors and mobile phone use. In this study, we proposed a method to estimate 3D distribution of the specific absorption rate (SAR) in the human head due to mobile phone use to provide the exposure gradient for epidemiological studies. 3D SAR distributions due to exposure to an electromagnetic field from mobile phones are estimated from mobile phone compliance testing data for actual devices. The data for compliance testing are measured only on the surface in the region near the device and in a small 3D region around the maximum on the surface in a homogeneous phantom with a specific shape. The method includes an interpolation/extrapolation and a head shape conversion. With the interpolation/extrapolation, SAR distributions in the whole head are estimated from the limited measured data. 3D SAR distributions in the numerical head models, where the tumor location is identified in the epidemiological studies, are obtained from measured SAR data with the head shape conversion by projection. Validation of the proposed method was performed experimentally and numerically. It was confirmed that the proposed method provided good estimation of 3D SAR distribution in the head, especially in the brain, which is the tissue of major interest in epidemiological studies. We conclude that it is possible to estimate 3D SAR distributions in a realistic head model from the data obtained by compliance testing measurements to provide a measure for the exposure gradient in specific locations of the brain for the purpose of exposure assessment in epidemiological studies. The proposed method has been used in several studies in the INTERPHONE.

• Acute ocular injuries caused by 60-Ghz millimeter-wave exposure.

  Authors: Masami Kojima, Masahiro Hanazawa, Yoko Yamashiro, Hiroshi Sasaki, Soichi Watanabe, Masao Taki, Yukihisa Suzuki, Akimasa Hirata, Yoshitsugu Kamimura, Kazuyuki Sasaki

  Health physics. 10/2009; 97(3):212-8.

  The goal of this study was to examine the clinical course of 60-GHz millimeter-wave induced damages to the rabbit eye and to report experimental conditions that allow reproducible induction of theseThe goal of this study was to examine the clinical course of 60-GHz millimeter-wave induced damages to the rabbit eye and to report experimental conditions that allow reproducible induction of these injuries. The eyes of pigmented rabbits (total number was 40) were irradiated with 60-GHz millimeter-waves using either a horn antenna or one of two lens antennas (6 and 9 mm diameter; phi6, phi9) Morphological changes were assessed by slit-lamp microscopy. Additional assessments included corneal fluorescein staining, iris fluorescein angiography, and lens epithelium light microscopy. Under the standardized eye-antenna positioning, the three antennas caused varying damages to the eyelids or eyeglobes. The most reproducible injuries without concurrent eyelid edema and corneal desiccation were achieved using the phi6 lens antenna: irradiation for 6 min led to an elevation of the corneal surface temperature (reaching 54.2 +/- 0.9 degrees C) plus corneal edema and epithelial cell loss. Furthermore, mitotic cells appeared in the pupillary area of the lens epithelium. Anterior uveitis also occurred resulting in acute miosis (from 6.6 +/- 1.4 to 2.2 +/- 1.4 mm), an increase in flares (from 6.7 +/- 0.9 to 334.3 +/- 130.8 photons per second), and iris vasodilation or vessel leakage. These findings indicate that the three types of millimeter-wave antennas can cause thermal injuries of varying types and levels. The thermal effects induced by millimeter-waves can apparently penetrate below the surface of the eye.

• In-situ electric field and current density in Japanese male and female models for uniform magnetic field exposures.

  Authors: Akimasa Hirata, Kanako Wake, Soichi Watanabe, Masao Taki

  Radiation protection dosimetry. 02/2009; 135(4):272-5.

  The present study quantified the in situ electric field and induced current density in anatomically based numeric Japanese male and female models for exposure to extremely low-frequency magneticThe present study quantified the in situ electric field and induced current density in anatomically based numeric Japanese male and female models for exposure to extremely low-frequency magnetic fields. A quasi-static FDTD method was applied to analyse this problem. The computational results obtained herein reveal that the 99 th percentile value of the in situ electric field in the nerve tissue and the current density averaged over an area of 1 cm(2) of the nerve tissue (excluding non-nerve tissues in the averaging region) in the female models were less than 35 and 25 %, respectively. These induced quantities in the Japanese models were smaller than those for European models reported in a previous study, which is mainly due to the difference in cross-sectional area of the body.

• Effects of short-term W-CDMA mobile phone base station exposure on women with or without mobile phone related symptoms.

  Authors: Toshiaki Furubayashi, Akira Ushiyama, Yasuo Terao, Yoko Mizuno, Kei Shirasawa, Pornanong Pongpaibool, Ally Y. Simba, Kanako Wake, Masami Nishikawa, Kaori Miyawaki [......] Shogo Hirota, Miyuki Takahashi, Tomoko Okano, Satomi Inomata-Terada, Shigeru Sokejima, Eiji Maruyama, Soichi Watanabe, Masao Taki, Chiyoji Ohkubo, Yoshikazu Ugawa

  Bioelectromagnetics. 10/2008;

  To investigate possible health effects of mobile phone use, we conducted a double-blind, cross-over provocation study to confirm whether subjects with mobile phone related symptoms (MPRS) are moreTo investigate possible health effects of mobile phone use, we conducted a double-blind, cross-over provocation study to confirm whether subjects with mobile phone related symptoms (MPRS) are more susceptible than control subjects to the effect of electromagnetic fields (EMF) emitted from base stations. We sent questionnaires to 5,000 women and obtained 2,472 valid responses from possible candidates; from these, we recruited 11 subjects with MPRS and 43 controls. There were four EMF exposure conditions, each of which lasted 30 min: continuous, intermittent, and sham exposure with and without noise. Subjects were exposed to EMF of 2.14 GHz, 10 V/m (W-CDMA), in a shielded room to simulate whole-body exposure to EMF from base stations, although the exposure strength we used was higher than that commonly received from base stations. We measured several psychological and cognitive parameters pre- and post-exposure, and monitored autonomic functions. Subjects were asked to report on their perception of EMF and level of discomfort during the experiment. The MPRS group did not differ from the controls in their ability to detect exposure to EMF; nevertheless they consistently experienced more discomfort, regardless of whether or not they were actually exposed to EMF, and despite the lack of significant changes in their autonomic functions. Thus, the two groups did not differ in their responses to real or sham EMF exposure according to any psychological, cognitive or autonomic assessment. In conclusion, we found no evidence of any causal link between hypersensitivity symptoms and exposure to EMF from base stations. Bioelectromagnetics (c) 2008 Wiley-Liss, Inc.

• Computation of temperature elevation in rabbit eye irradiated by 2.45-GHz microwaves with different field configurations.

  Authors: Akimasa Hirata, Soichi Watanabe, Masao Taki, Osamu Fujiwara, Masami Kojima, Kazuyuki Sasaki

  Health physics. 03/2008; 94(2):134-44.

  This study calculated the temperature elevation in the rabbit eye caused by 2.45-GHz near-field exposure systems. First, we calculated specific absorption rate distributions in the eye for differentThis study calculated the temperature elevation in the rabbit eye caused by 2.45-GHz near-field exposure systems. First, we calculated specific absorption rate distributions in the eye for different antennas and then compared them with those observed in previous studies. Next, we re-examined the temperature elevation in the rabbit eye due to a horizontally-polarized dipole antenna with a C-shaped director, which was used in a previous study. For our computational results, we found that decisive factors of the SAR distribution in the rabbit eye were the polarization of the electromagnetic wave and antenna aperture. Next, we quantified the eye average specific absorption rate as 67 W kg(-1) for the dipole antenna with an input power density at the eye surface of 150 mW cm(-2), which was specified in the previous work as the minimum cataractogenic power density. The effect of administrating anesthesia on the temperature elevation was 30% or so in the above case. Additionally, the position where maximum temperature in the lens appears is discussed due to different 2.45-GHz microwave systems. That position was found to appear around the posterior of the lens regardless of the exposure condition, which indicates that the original temperature distribution in the eye was the dominant factor.

• SAR characterization inside intracranial tumors for case-control epidemiological studies on cellular phones and RF exposure.

  Authors: Nadège Varsier, Kanako Wake, Masao Taki, Soichi Watanabe, Toru Takebayashi, Naohito Yamaguchi, Yuriko Kikuchi

  Annales des Télécommunications. 01/2008; 63:65-78.

• Lack of promoting effects of chronic exposure to 1.95-GHz W-CDMA signals for IMT-2000 cellular system on development of N-ethylnitrosourea-induced central nervous system tumors in F344 rats.

  Authors: Tomoyuki Shirai, Toshio Ichihara, Kanako Wake, So-ichi Watanabe, Yukio Yamanaka, Mayumi Kawabe, Masao Taki, Osamu Fujiwara, Jianqing Wang, Satoru Takahashi, Seiko Tamano

  Bioelectromagnetics. 11/2007; 28(7):562-72.

  The present study was performed to evaluate effects of a 2-year exposure to an electromagnetic near-field (EMF) equivalent to that generated by cellular phones on tumor development in the centralThe present study was performed to evaluate effects of a 2-year exposure to an electromagnetic near-field (EMF) equivalent to that generated by cellular phones on tumor development in the central nervous system (CNS) of rats. For this purpose, pregnant F344 rats were given a single administration of N-ethylnitrosourea (ENU) on gestational day 18. A total of 500 pups were divided into five groups, each composed of 50 males and 50 females: Group 1, untreated controls; Group 2, ENU alone; Groups 3 to 5, ENU + EMF (sham exposure and two exposure levels). A 1.95-GHz wide-band code division multiple access (W-CDMA) signal, which is a feature of the International Mobile Telecommunication 2000 (IMT-2000) cellular system was employed for exposure of the rat head starting from 5 weeks of age, 90 min a day, 5 days a week, for 104 weeks. Brain average specific absorption rates (SARs) were designed to be .67 and 2.0 W/kg for low and high exposures, respectively. The incidence and numbers of brain tumors in female rats exposed to 1.95-GHz W-CDMA signals showed tendencies to increase but without statistical significance. Overall, no significant increase in incidences or numbers, either in the males or females, was detected in the EMF-exposed groups. In addition, no clear changes in tumor types in the brain were evident. Thus, under the present experimental conditions, exposure of heads of rats to 1.95-GHz W-CDMA signals for IMT-2000 for a 2-year period was not demonstrated to accelerate or otherwise affect ENU-initiated brain tumorigenesis.

• Development of a 2.45-GHz Local Exposure System for In Vivo Study on Ocular Effects

  Authors: K. Wake, H. Hongo, S. Watanabe, Masao Taki, Y. Kamimura, Y. Yamanaka, T. Uno, M. Kojima, I. Hata, K. Sasaki

  Microwave Theory and Techniques, IEEE Transactions on. 04/2007;

  We developed a new exposure system to irradiate microwaves locally on a rabbit eye using a small coaxial-to-waveguide adapter filled with low-loss dielectric material as an antenna. A numericalWe developed a new exposure system to irradiate microwaves locally on a rabbit eye using a small coaxial-to-waveguide adapter filled with low-loss dielectric material as an antenna. A numerical rabbit model was also developed using X-ray computer tomography images, and the specific absorption rates (SARs) in the rabbit, especially in the eye, were analyzed with the finite-difference time-domain method. The temperature elevation in the exposed eye was also evaluated by solving a bioheat equation. Our exposure system can generate incident power density of 15 mW/cm² at the surface of a rabbit eye with input power of 1 W. When the incident power density on the rabbit eye is 300 mW/cm², average SAR over the exposed eye and the whole body were approximately 108 and 1.8 W/kg, respectively. The exposure system can realize localized exposure to the eye with the ratio of exposed-eye averaged SAR to the whole-body averaged SAR was 60. The developed exposure system can achieve high-intensity exposure such as the threshold of cataracts, i.e., the eye-averaged SAR over 100 W/kg or the lens temperature over 41 degC with the incident power density of 300mW/cm² without significant whole-body thermal stresses

• Effects of 2.45 GHz electromagnetic fields with a wide range of SARs on bacterial and HPRT gene mutations.

  Authors: Shin Koyama, Yoshio Takashima, Tomonori Sakurai, Yukihisa Suzuki, Masao Taki, Junji Miyakoshi

  Journal of radiation research. 02/2007; 48(1):69-75.

  Present day use of mobile phones is ubiquitous. This causes some concern for human health due to exposure to high-frequency electromagnetic fields (HFEMF) from mobile phones. Consequently, we havePresent day use of mobile phones is ubiquitous. This causes some concern for human health due to exposure to high-frequency electromagnetic fields (HFEMF) from mobile phones. Consequently, we have examined the effects of 2.45 GHz electromagnetic fields on bacterial mutations and the hypoxanthine-guanine phosphoribosyl transferase (HPRT) gene mutations. Using the Ames test, bacteria were exposed to HFEMF for 30 min at specific absorption rates (SARs) from 5 to 200 W/kg. In all strains, there was no significant difference in the frequency of revertant colonies between sham exposure and HFEMF-exposed groups. In examination of mutations of the HPRT gene, Chinese hamster ovary (CHO)-K1 cells were exposed to HFEMF for 2 h at SARs from 5 to 200 W/kg. We detected a combination effect of simultaneous exposure to HFEMF and bleomycin at the respective SARs. A statistically significant difference was observed between the cells exposed to HFEMF at the SAR of 200 W/kg. Cells treated with the combination of HFEMF at SARs from 50 to 200 W/kg and bleomycin exhibited increased HPRT mutations. As the exposure to HFEMF induced an increase in temperature, these increases of mutation frequency may be a result of activation of bleomycin by heat. We consider that the increase of mutation frequency may be due to a thermal effect.

• The INTERPHONE study: design, epidemiological methods, and description of the study population.

  Authors: Elisabeth Cardis, Lesley Richardson, Isabelle Deltour, Bruce Armstrong, Maria Feychting, Christoffer Johansen, Monique Kilkenny, Patricia McKinney, Baruch Modan, Siegal Sadetzki [......] Brigitte Schlehofer, Jack Siemiatycki, Masao Taki, Toru Takebayashi, Tore Tynes, Martie van Tongeren, Paolo Vecchia, Joe Wiart, Alistair Woodward, Naohito Yamaguchi

  European journal of epidemiology. 02/2007; 22(9):647-64.

  The very rapid worldwide increase in mobile phone use in the last decade has generated considerable interest in the possible health effects of exposure to radio frequency (RF) fields. A multinationalThe very rapid worldwide increase in mobile phone use in the last decade has generated considerable interest in the possible health effects of exposure to radio frequency (RF) fields. A multinational case-control study, INTERPHONE, was set-up to investigate whether mobile phone use increases the risk of cancer and, more specifically, whether the RF fields emitted by mobile phones are carcinogenic. The study focused on tumours arising in the tissues most exposed to RF fields from mobile phones: glioma, meningioma, acoustic neurinoma and parotid gland tumours. In addition to a detailed history of mobile phone use, information was collected on a number of known and potential risk factors for these tumours. The study was conducted in 13 countries. Australia, Canada, Denmark, Finland, France, Germany, Israel, Italy, Japan, New Zealand, Norway, Sweden, and the UK using a common core protocol. This paper describes the study design and methods and the main characteristics of the study population. INTERPHONE is the largest case-control study to date investigating risks related to mobile phone use and to other potential risk factors for the tumours of interest and includes 2,765 glioma, 2,425 meningioma, 1,121 acoustic neurinoma, 109 malignant parotid gland tumour cases and 7,658 controls. Particular attention was paid to estimating the amount and direction of potential recall and participation biases and their impact on the study results.

• Computational verification of anesthesia effect on temperature variations in rabbit eyes exposed to 2.45 GHz microwave energy.

  Authors: Akimasa Hirata, Soichi Watanabe, Masami Kojima, Ikuho Hata, Kanako Wake, Masao Taki, Kazuyuki Sasaki, Osamu Fujiwara, Toshiyuki Shiozawa

  Bioelectromagnetics. 01/2007; 27(8):602-12.

  This paper computationally verifies the effect of anesthesia on temperature variations in the rabbit eye due to microwave energy. The main reason for this investigation is that our previous paperThis paper computationally verifies the effect of anesthesia on temperature variations in the rabbit eye due to microwave energy. The main reason for this investigation is that our previous paper suggested a reduction in blood flow due to the administration of anesthesia, resulting in an overestimated temperature increase. However, no quantitative investigation has yet been conducted. The finite-difference time-domain (FDTD) method is used for calculating power absorption and temperature variation in rabbits. For this purpose, we used a computational rabbit phantom, which is comprised of 12 tissues (including 6 eye tissues) with a resolution of 1 mm. Thermal constants of the rabbit were derived by comparing measured and calculated temperatures. For intense microwave exposure to the rabbit eye, time courses of calculated and measured temperatures were in good agreement for cases both with and without the administration of anesthesia. The point to be stressed is that under anesthesia the thermoregulatory response was inactivated and blood flow and basal metabolism was reduced.

• Effects of continuous and intermittent exposure to RF fields with a wide range of SARs on cell growth, survival, and cell cycle distribution.

  Authors: Yoshio Takashima, Hideki Hirose, Shin Koyama, Yukihisa Suzuki, Masao Taki, Junji Miyakoshi

  Bioelectromagnetics. 08/2006; 27(5):392-400.

  To examine the biological effects of radio frequency (RF) electromagnetic fields in vitro, we have examined the fundamental cellular responses, such as cell growth, survival, and cell cycleTo examine the biological effects of radio frequency (RF) electromagnetic fields in vitro, we have examined the fundamental cellular responses, such as cell growth, survival, and cell cycle distribution, following exposure to a wide range of specific absorption rates (SAR). Furthermore, we compared the effects of continuous and intermittent exposure at high SARs. An RF electromagnetic field exposure unit operating at a frequency of 2.45 GHz was used to expose cells to SARs from 0.05 to 1500 W/kg. When cells were exposed to a continuous RF field at SARs from 0.05 to 100 W/kg for 2 h, cellular growth rate, survival, and cell cycle distribution were not affected. At 200 W/kg, the cell growth rate was suppressed and cell survival decreased. When the cells were exposed to an intermittent RF field at 300 W/kg(pk), 900 W/kg(pk) and 1500 W/kg(pk) (100 W/kg(mean)), no significant differences were observed between these conditions and intermittent wave exposure at 100 W/kg. When cells were exposed to a SAR of 50 W/kg for 2 h, the temperature of the medium around cells rose to 39.1 degrees C, 100 W/kg exposure increased the temperature to 41.0 degrees C, and 200 W/kg exposure increased the temperature to 44.1 degrees C. Exposure to RF radiation results in heating of the medium, and the thermal effect depends on the mean SAR. Hence, these results suggest that the proliferation disorder is caused by the thermal effect.

• Effect of high-frequency electromagnetic fields with a wide range of SARs on chromosomal aberrations in murine m5S cells.

  Authors: Yoshiki Komatsubara, Hideki Hirose, Tomonori Sakurai, Shin Koyama, Yukihisa Suzuki, Masao Taki, Junji Miyakoshi

  Mutation research. 12/2005; 587(1-2):114-9.

  To investigate the induction of chromosomal aberrations in mouse m5S cells after exposure to high-frequency electromagnetic fields (HFEMFs) at 2.45 GHz, cells were exposed for 2 h at average specificTo investigate the induction of chromosomal aberrations in mouse m5S cells after exposure to high-frequency electromagnetic fields (HFEMFs) at 2.45 GHz, cells were exposed for 2 h at average specific absorption rates (SARs) of 5, 10, 20, 50 and 100 W/kg with continuous wave-form (CW), or at a mean SAR of 100 W/kg (with a maximum of 900 W/kg) with pulse wave-form (PW). The effects of HFEMF exposure were compared with those in sham-exposed controls and with mitomycin C (MMC) or X-ray treatment as positive controls. We examined all structural, chromatid-type and chromosome-type changes after HFEMF exposures and treatments with MMC and X-rays. No significant differences were observed following exposure to HFEMFs at SARs from 5 to 100 W/kg CW and at a mean SAR of 100 W/kg PW (a maximum SAR of 900 W/kg) compared with sham-exposed controls, whereas treatments with MMC and X-rays increased the frequency of chromatid-type and chromosome-type aberrations. In summary, HFEMF exposures at 2.45 GHz for 2 h with up to 100 W/kg SAR CW and an average 100 W/kg PW (a maximum SAR of 900 W/kg) do not induce chromosomal aberrations in m5S cells. Furthermore, there was no difference between exposures to CW and PW HFEMFs.

• Effects of 2450 MHz electromagnetic fields with a wide range of SARs on methylcholanthrene-induced transformation in C3H10T1/2 cells.

  Authors: Jin Wang, Tomonori Sakurai, Shin Koyama, Yoshiki Komatubara, Yukihisa Suzuki, Masao Taki, Junji Miyakoshi

  Journal of radiation research. 10/2005; 46(3):351-61.

  This study examined whether 2450 MHz continuous wave high frequency electromagnetic fields (HFEMF) could induce cancer-like changes in mouse C3H10T1/2 cells, and whether HFEMF could initiateThis study examined whether 2450 MHz continuous wave high frequency electromagnetic fields (HFEMF) could induce cancer-like changes in mouse C3H10T1/2 cells, and whether HFEMF could initiate malignant or synergistic transformation. Transformed foci, Type II and Type III, were independently counted as the experiment endpoint. The cells were exposed to HFEMF alone at a wide range of specific absorption rates (SARs) of 5 to 200 W/kg for 2 h and/or were treated with a known initiating chemical, methylcholanthrene (MC) (2.5 microg/ml). No significant differences were observed in the malignant transformation (Type II + Type III) frequency between the controls and HFEMF with or without 12-O-tetradecanoylphorbol-13-acetate (TPA) (0.5 ng/ml), a tumor promoter that could enhance transformation frequency initiated by MC in multistage carcinogenesis. However, the transformation frequency for HFEMF at SAR of more than 100 W/kg with MC or MC plus TPA was increased compared with MC alone or MC plus TPA. On the other hand, the corresponding heat groups (heat alone, heat + MC, and heat + MC + TPA) did not increase transformation compared with each control level in C3H10T1/2 cells. This result suggests that 2450 MHz HFEMF could not contribute to the initiation stage of tumor formation, but it may contribute to the promotion stage at the extremely high SAR (100 W/kg).

• Chronic exposure to a 1.439 GHz electromagnetic field used for cellular phones does not promote N-ethylnitrosourea induced central nervous system tumors in F344 rats.

  Authors: Tomoyuki Shirai, Mayumi Kawabe, Toshio Ichihara, Osamu Fujiwara, Masao Taki, So-ichi Watanabe, Kanako Wake, Yukio Yamanaka, Katsumi Imaida, Makoto Asamoto, Seiko Tamano

  Bioelectromagnetics. 02/2005; 26(1):59-68.

  The present study was designed to evaluate whether a 2 year exposure to an electromagnetic field (EMF) equivalent to that generated by cellular phones can accelerate tumor development in the centralThe present study was designed to evaluate whether a 2 year exposure to an electromagnetic field (EMF) equivalent to that generated by cellular phones can accelerate tumor development in the central nervous system (CNS) of rats. Brain tumorigenesis was initiated by an intrauterine exposure to N-ethylnitrosourea (ENU) on gestational day 18. A total of 500 pups were divided into five groups, each composed of 50 males and 50 females: Group 1, untreated control; Group 2, ENU alone; Groups 3-5, ENU + EMF (sham exposure and 2 exposure levels). A 1.439 GHz time division multiple access (TDMA) signal for the Personal Digital Cellular (PDC), Japanese standard cellular system was used for the exposure of the rat head starting from 5 weeks of age, 90 min a day, 5 days a week, for 104 weeks. Brain average specific absorption rate (SAR) was 0.67 and 2.0 W/kg for low and high exposures, respectively: whole body average SAR was less than 0.4 W/kg. There were no inter-group differences in body weights, food consumption, and survival rates. No increase in the incidences or numbers per group of brain and/or spinal cord tumors, either in the males or females, was detected in the EMF exposed groups. In addition, no clear changes in tumor types were evident. Thus, under the present experimental conditions, 1.439 GHz EMF exposure to the heads of rats for a 2 year period was not demonstrated to accelerate or affect ENU initiated brain tumorigenesis.

• Short term exposure to 1439 MHz pulsed TDMA field does not alter melatonin synthesis in rats.

  Authors: Keisuke Hata, Hironori Yamaguchi, Giichirou Tsurita, Soichi Watanabe, Kanako Wake, Masao Taki, Shoogo Ueno, Hirokazu Nagawa

  Bioelectromagnetics. 02/2005; 26(1):49-53.

  The widespread use of the mobile phone has initiated many studies on the possible adverse effects of a high frequency electromagnetic field (EMF), which is used in mobile phones. A low frequency EMFThe widespread use of the mobile phone has initiated many studies on the possible adverse effects of a high frequency electromagnetic field (EMF), which is used in mobile phones. A low frequency EMF is reported to suppress melatonin synthesis. The aim of this study was to clarify the effects on melatonin synthesis in rats after short term exposure to a 1439 MHz time division multiple access (TDMA) EMF. The average specific absorption ratio (SAR) of the brain was 7.5 W/kg, and the average SARs of the whole body were 1.9 and 2.0 W/kg for male and female rats, respectively. A total of 208 male and female rats were investigated. After acclimatization to a 12 h light-dark (LD) cycle, serum and pineal melatonin levels together with pineal serotonin level under a dark condition (less than 1 lux) were examined by radioimmunoassay. No significant differences in melatonin and serotonin levels were observed between the exposure, sham, and cage control groups. These results suggest that short term exposure to a 1439 MHz TDMA EMF, which is about four times stronger than that emitted by mobile phones, does not alter melatonin and serotonin synthesis in rats. Further investigations on the effects of long term exposure are warranted.

• Electromagnetic and Thermal Dosimetry of a Cylindrical Waveguide-Type

  Authors: Tomohide Sonoda, Rui Tokunaga, Koichi Seto, Yukihisa Suzuki, Kanako Wake, Soichi Watanabe, Masao Taki

  IEICE Transactions. 01/2005; 88-B:3287-3293.