Kanako Wake

Distribution of RF energy emitted by mobile phones in anatomical structures of the brain

The rapid worldwide increase in mobile phone use in the last decade has generated considerable interest in possible carcinogenic effects of radio frequency (RF). Because exposure to RF from phones is localized, if a risk exists it is likely to be greatest for tumours in regions with greatest energy absorption. The objective of the current paper was to characterize the spatial distribution of RF energy in the brain, using results of measurements made in two laboratories on 110 phones used in Europe or Japan. Most (97-99% depending on frequency) appears to be absorbed in the brain hemisphere on the side where the phone is used, mainly (50-60%) in the temporal lobe. The average relative SAR is highest in the temporal lobe (6-15%, depending on frequency, of the spatial peak SAR in the most exposed region of the brain) and the cerebellum (2-10%) and decreases very rapidly with increasing depth, particularly at higher frequencies. The SAR distribution appears to be fairly similar across phone models, between older and newer phones and between phones with different antenna types and positions. Analyses of risk by location of tumour are therefore important for the interpretation of results of studies of brain tumours in relation to mobile phone use.

Mobile phone use, exposure to radiofrequency electromagnetic field, and brain tumour: a case-control study

In a case–control study in Japan of brain tumours in relation to mobile phone use, we used a novel approach for estimating the specific absorption rate (SAR) inside the tumour, taking account of spatial relationships between tumour localisation and intracranial radiofrequency distribution. Personal interviews were carried out with 88 patients with glioma, 132 with meningioma, and 102 with pituitary adenoma (322 cases in total), and with 683 individually matched controls. All maximal SAR values were below 0.1 W kg−1, far lower than the level at which thermal effects may occur, the adjusted odds ratios (ORs) for regular mobile phone users being 1.22 (95% confidence interval (CI): 0.63–2.37) for glioma and 0.70 (0.42–1.16) for meningioma. When the maximal SAR value inside the tumour tissue was accounted for in the exposure indices, the overall OR was again not increased and there was no significant trend towards an increasing OR in relation to SAR-derived exposure indices. A non-significant increase in OR among glioma patients in the heavily exposed group may reflect recall bias.

Mobile phone use and acoustic neuroma risk in Japan

Objectives: The rapid increase of mobile phone use has increased public concern about its possible health effects in Japan, where the mobile phone system is unique in the characteristics of its signal transmission. To examine the relation between mobile phone use and acoustic neuroma, a case-control study was initiated. Methods: The study followed the common, core protocol of the international collaborative study, INTERPHONE. A prospective case recruitment was done in Japan for 2000–04. One hundred and one acoustic neuroma cases, who were 30–69 years of age and resided in the Tokyo area, and 339 age, sex, and residency matched controls were interviewed using a common computer assisted personal interview system. Education and marital status adjusted odds ratio was calculated with a conditional logistic regression analysis. Results: Fifty one cases (52.6%) and 192 controls (58.2%) were regular mobile phone users on the reference date, which was set as one year before the diagnosis, and no significant increase of acoustic neuroma risk was observed, with the odds ratio (OR) being 0.73 (95% CI 0.43 to 1.23). No exposure related increase in the risk of acoustic neuroma was observed when the cumulative length of use (<4 years, 4–8 years, >8 years) or cumulative call time (<300 hours, 300–900 hours, >900 hours) was used as an exposure index. The OR was 1.09 (95% CI 0.58 to 2.06) when the reference date was set as five years before the diagnosis. Further, laterality of mobile phone use was not associated with tumours. Conclusions: These results suggest that there is no significant increase in the risk of acoustic neuroma in association with mobile phone use in Japan.

Lack of Adverse Effects of Whole-Body Exposure to a Mobile Telecommunication Electromagnetic Field on the Rat Fetus

Abstract The recent steep increase in the number of users of cellular phones is resulting in marked increase of exposure of humans to radiofrequency electromagnetic fields (EMFs). Children are of particular concern. Our goal was to evaluate potential adverse effects of long-term whole-body exposure to EMFs simulating those from base stations for cellular phone communication. Pregnant rats were given low, high or no exposure. At the high level, the average specific absorption rate (SAR)for the dams was 0.066–0.093 W/kg. The SAR for the fetuses and the F1 progeny was 0.068–0.146 W/kg. At the low level, the SARs were about 43% of these. The 2.14 GHz signals were applied for 20 h per day during the gestation and lactation periods. No abnormal findings were observed in either the dams or the F1 generation exposed to the EMF or in the F2 offspring. Parameters evaluated included growth, gestational condition and organ weights for dams and survival rates, development, growth, physical and functional development, hormonal status, memory function and reproductive ability of the F1 offspring (at 10 weeks of age) along with embryotoxicity and teratogenicity in the F2 rats. Thus, under our experimental conditions, whole-body exposure to 2.14 GHz for 20 h per day during gestation and lactation did not cause any adverse effects on pregnancy or the development of rats.

Incident Electric Field Effect and Numerical Dosimetry for a Wireless Power Transfer System Using Magnetically Coupled Resonances

We conducted a dosimetry study of a wireless power transfer (WPT) system, which is based on magnetically coupled resonances. The electric and magnetic fields produced by the system have been calculated using the method of moments. We calculated the induced electric fields and the specific absorption rates in a Japanese adult male model by the scattered-field finite-difference time-domain method, taking into account both the incident electric and magnetic fields, and also by the impedance method, but only taking into account the incident magnetic fields. We discuss the differences between the results obtained by the two methods. We also discuss the compliance of the WPT system with international safety guidelines.

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

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 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.

Intercomparison of induced fields in Japanese male model for ELF magnetic field exposures: effect of different computational methods and codes

The present study provides an intercomparison of the induced quantities in a human model for uniform magnetic field exposures at extremely low frequency. A total of six research groups have cooperated in this joint intercomparison study. The computational conditions and numeric human phantom including the conductivity of tissue were set identically to focus on the uncertainty in computed fields. Differences in the maximal and 99th percentile value of the in situ electric field were less than 30 and 10 % except for the results of one group. Differences in the current density averaged over 1 cm(2) of the central nerve tissue are 10 % or less except for the results of one group. This comparison suggests that the computational uncertainty of the in situ electric field/current density due to different methods and coding is smaller than that caused by different human phantoms and the conductivitys of tissue, which was reported in a previous study.

Effects of gestational exposure to 1.95-GHz W-CDMA signals for IMT-2000 cellular phones: Lack of embryotoxicity and teratogenicity in rats

The present study was designed to evaluate whether gestational exposure to an EMF targeting the head region, similar to that from cellular phones, might affect embryogenesis in rats. A 1.95-GHz wide-band code division multiple access (W-CDMA) signal, which is one applied for the International Mobile Telecommunication 2000 (IMT-2000) system and used for the freedom of mobile multimedia access (FOMA), was employed for exposure to the heads of four groups of pregnant CD(SD) IGS rats (20 per group) for gestational days 7-17. The exposure was performed for 90 min/day in the morning. The spatial average specific absorption rate (SAR) for individual brains was designed to be 0.67 and 2.0 W/kg with peak brain SARs of 3.1 and 7.0 W/kg for low (group 3) and high (group 4) exposures, respectively, and a whole-body average SAR less than 0.4 W/kg so as not to cause thermal effects due to temperature elevation. Control and sham exposure groups were also included. At gestational day 20, all dams were killed and fetuses were taken out by cesarean section. There were no differences in maternal body weight gain. No adverse effects of EMF exposure were observed on any reproductive and embryotoxic parameters such as number of live (243-271 fetuses), dead or resorbed embryos, placental weights, sex ratios, weights or external, visceral or skeletal abnormalities of live fetuses.

Development and Dosimetry Analysis of a 2-GHz Whole-Body Exposure Setup for Unrestrained Pregnant and Newborn Rats

For investigation of possible bio-effects of the 2-GHz wideband code division multiple access cellular system on pregnant and newborn rats, we have developed an unrestrained whole-body exposure setup, which employs two dipole antennas to induce a circularly polarized field at the location of the rats. The dosimetric results, by using the finite-difference time-domain method in conjunction with anatomical rat models, have confirmed the realization of a circular polarization in the exposure space, and have also revealed that the exposure setup can maintain a relative variation of the whole-body average specific absorption rate (SAR) within plusmn60% of the designed average level for various positions of rats. These findings show that the exposure setup is reasonable and acceptable in view of the actual SAR variation in a human body due to RF exposure from base stations.

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

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 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