Ally Y. Simba

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.

Specific Absorption Rates of Anatomically Realistic Human Models Exposed to RF Electromagnetic Fields From Mobile Phones Used in Elevators

This paper presents a detailed numerical investigation to determine whether or not an increased specific absorption rate (SAR) in an adult using a mobile phone inside an elevator due to the multireflections of electromagnetic fields from the walls exceed the RF-exposure guidelines. A fully realistic heterogeneous human body model and an actual elevator size were employed. The nonuniform mesh finite-difference time-domain technique and a supercomputer were employed to obtain the SAR and other important parameters. The mobile phone was modeled as a lambda/2 dipole antenna placed at a distance of 16 mm from the head. For computations, operating frequencies of 900, 1500, and 2000 MHz with transmitting power of 250 mW were used. Computed results show that the peak spatial-average 10-g SAR depends on the position of the passenger and the antenna against the elevator walls. We observed a substantial increase in the whole-body average SAR and peak 10-g SAR values of the passenger in the elevator over their respective free-space values. However, the maximum values obtained do meet the basic restrictions described in the international RF safety guidelines. For example, the maximum values of the whole-body average and peak spatial-average SAR were 4.4% and 78% of the international RF safety guideline, respectively.

Effects of electromagnetic fields emitted from W-CDMA-like mobile phones on sleep in humans.

In this study, we investigated subjective and objective effects of mobile phones using a Wideband Code Division Multiple Access (W-CDMA)-like system on human sleep. Subjects were 19 volunteers. Real or sham electromagnetic field (EMF) exposures for 3 h were performed before their usual sleep time on 3 consecutive days. They were exposed to real EMF on the second or third experimental day in a double-blind design. Sleepiness and sleep insufficiency were evaluated the next morning. Polysomnograms were recorded for analyses of the sleep variables and power spectra of electroencephalograms (EEG). No significant differences were observed between the two conditions in subjective feelings. Sleep parameters including sleep stage percentages and EEG power spectra did not differ significantly between real and sham exposures. We conclude that continuous wave EMF exposure for 3 h from a W-CDMA-like system has no detectable effects on human sleep.

Measurement of the maximum SAR in a spherical phantom when operating a mobile phone near a metallic wall

The aim of this paper is to present an experimental investigation of the specific absorption rate (SAR) in a spherical phantom head when operating a mobile phone close to a metallic wall. The mobile phone is modeled as a half-wavelength dipole antenna. The effect of the wall on the peak 10-g SAR and input characteristics of the antenna for two wall orientations are measured. The antenna is set to transmit maximum output power of 250 mW at 900 MHz. A slowly decaying sinusoidal form of the peak 10-g SAR curves, which has been predicted by numerical simulation from several authors including ourselves, is confirmed experimentally for the first time. Under the valid antenna-wall distances used in this work, maximum peak 10-g SAR increase of 7% over the free space value was recorded at the distance of 394 mm away from the wall. Simulated results obtained by the FDTD technique are also presented. Good agreement between the measured and simulated results is obtained.

A review of mobile phone usage in enclosed areas and RF safety guideline

The use of mobile phones in metallic enclosed environments such as elevators, train cars and even airplanes has attract a lot of attention in recent years. In these environments, most of the radio frequency (RF) energy from mobile phones remains inside due to the lack of escape routes, resulting in possibility of the field levels exceeding limits described in the international RF safety guidelines. This has resulted in an anxiety on possible health effects of passengers in these environments. In this review paper, size of the passengers (child vs. adult human model), method of investigation (theory vs. numerical), passenger position, elevator structure etc., are briefly discussed to determine how they affect the RF exposure. We also discuss few experimental investigation related to this problem for the passenger using a mobile phone near a metallic wall. Our objective is to provide an understanding of the SAR characteristics of the mobile phone user in such environment and how these characteristics are affected by the aforementioned factors.

Numerical estimation of EMI impact on implantable cardiac pacemakers in elevator using EMF distributions inside human body

In recent years, mobile phone usage has extended to a wide range of environment such as places surrounded by conductive surfaces, e.g., train carriages, elevators, and airplanes. There have been concerns that cellular radio can interfere with different types of devices and increased usage in multi-reflection environments has led to concern about the possible effect of electromagnetic interference (EMI) on implantable medical devices (IMDs). Many experimental studies have been carried out in order to assess the EMI generated by cellular radio in free-space and experienced by IMDs including implantable cardiac pacemakers and implantable cardioverter defibrillators (ICDs) [1]-[3]. However, few studies have addressed the effect of EMI on IMDs in elevators. Precise and efficient methods of measuring the electric field (E-field) strength in different regions of multi-reflection environments have not been advanced due to the disturbed fields caused by the presence of measurement equipment and/or human bodies. Therefore, this is achieved by carrying out precise numerical simulations using the Finite-Difference-Time-Domain method [4]. We have already carried out numerical simulations on homogeneous human phantom models and some elevator models to investigate the EMI impact to implantable cardiac pacemakers in elevators; we examined the E-field distribution on the horizontal plane inside elevator [5], outside of human body. In this paper, we introduce our method for estimating pacemaker EMI using EMF distributions inside the region of the human body into which pacemakers are implanted. This enables us to carry out quantitative evaluations of the EMI impact to pacemakers by cellular radio transmission. In order to examine the complex situations where human is present in elevators, our analysis considered a realistically-shaped and anatomically-correct human phantom model. All calculations were run on a supercomputer.

Comparison of induced ankle currents of the human-body equivalent antennas and anatomically human models exposed to nearby monopole antennas

In this paper, the induced ankle currents of the liquid-type human-body equivalent antennas are compared to those of their corresponding Japanese adult male and female models when exposed to monopole antennas placed at a distance of 3 m away. The purpose is to determining if they will be in good agreement like the case of plane wave exposure from which they were designed. The investigation of the monopole antennas exposure is important, because they have been used to provide experimental validation of the performance of the equivalent antennas. Our results indicate that good agreement in induced ankle current is obtained for the frequencies above 45 MHz. This may be explained by the fact that at the frequencies above 45 MHz, at 3 m distance away, the equivalent antennas appear to be at far fields of the monopole antennas, at which the fields becomes almost like those of the plane wave.

Exposure system for a study of effects of mobile phones to human sleep and its dosimetry evaluation using numerical mobile phone

An exposure system for human provocation studies has been developed for the experiment on the effect of electromagnetic field exposure from mobile phone to the human sleep. The mobile phone, with an uplink of 1950 MHz, is configured to transmit the maximum output power of 250 mW. The results from the actual experiment for prolonged exposure of 3 hours have not shown any adverse effect of the EMF from mobile phone on the sleep of the human volunteers. We have also evaluated the specific absorption rate in the head of the adult Japanese human model using numerical phone modeled based on the shape and antenna used in the actual mobile phone employed in the experiment. The specific absorption rate was evaluated using finite-difference time-domain. Small values of SAR, i.e., less than 0.2 W/kg, were observed in the brain, with

Basic investigation of the measurements of W-CDMA signal from mobile phone base station

This paper presents a preliminary study of the measurements of W-CDMA signal from mobile phone base station. The measurements are carried out inside an anechoic chamber. We employed a base station simulator and the frequency selective method using Narda Probe. We investigated the effect of the spectrum analyzer settings on the measurements of the electric field strength for different resolution bands widths (RBWs), i.e., 50, 500, and 5000 kHz. The difference of the measured electric fields between these RBWs was less than 1.6 dB.