ABSTRACT
OBJECTIVES: The output power of a mobile phone is directly related to its radiofrequency (RF) electromagnetic field strength, and may theoretically vary substantially in different networks and phone use circumstances due to power control technologies. To improve indices of RF exposure for epidemiological studies, we assessed determinants of mobile phone output power in a multinational study. METHODS: More than 500 volunteers in 12 countries used Global System for Mobile communications software-modified phones (GSM SMPs) for approximately 1 month each. The SMPs recorded date, time, and duration of each call, and the frequency band and output power at fixed sampling intervals throughout each call. Questionnaires provided information on the typical circumstances of an individual's phone use. Linear regression models were used to analyse the influence of possible explanatory variables on the average output power and the percentage call time at maximum power for each call. RESULTS: Measurements of over 60,000 phone calls showed that the average output power was approximately 50% of the maximum, and that output power varied by a factor of up to 2 to 3 between study centres and network operators. Maximum power was used during a considerable proportion of call time (39% on average). Output power decreased with increasing call duration, but showed little variation in relation to reported frequency of use while in a moving vehicle or inside buildings. Higher output powers for rural compared with urban use of the SMP were observed principally in Sweden where the study covered very sparsely populated areas. CONCLUSIONS: Average power levels are substantially higher than the minimum levels theoretically achievable in GSM networks. Exposure indices could be improved by accounting for average power levels of different telecommunications systems. There appears to be little value in gathering information on circumstances of phone use other than use in very sparsely populated regions.
Subject(s)
Cell Phone/statistics & numerical data , Environmental Exposure/analysis , Radio Waves , Adult , Case-Control Studies , Environmental Exposure/statistics & numerical data , Female , Humans , Male , Middle Aged , Radiation Dosage , Radiation Monitoring/methods , Rural Health/statistics & numerical data , Time Factors , Urban Health/statistics & numerical dataABSTRACT
A wire patch cell (WPC) operating at the uplink frequency band of GSM 1800 MHz has been designed for in vitro experiments with the aim of investigating the possible biological effects of electromagnetic radiation associated with cellular phones. The 1800 MHz WPC design is a direct descendant of the original 900 MHz WPC introduced by Laval et al. This system provides a homogeneous specific absorption rate distribution, using four 3.5 cm petri dishes simultaneously. Numerical dosimetry has been performed using a commercial code (CST Microwave Studio), in order to evaluate accurately the efficiency of the structure (in terms of W kg(-1) per 1 W input power) and the distribution in the chosen biological target. The numerical results have been confirmed by experimental measurements performed by measuring thermal increase due to a high power impulse. The efficiency of the structure is 1.25 +/- 25% W kg(-1) per 1 W input power higher than the efficiency of the 900 MHz WPC. A few adjustments have been made in order to use the WPC in a standard incubator and to avoid thermal increases related to the radio frequency exposure. This exposure system has been adopted for the experiments scheduled in the RAMP and GUARD projects (VFPE).
Subject(s)
Electromagnetic Fields , Radio Waves , Radiometry/instrumentation , Radiometry/methods , Cell Phone , Electromagnetic Phenomena , Humans , In Vitro Techniques , Temperature , Time FactorsABSTRACT
Measurements in the real environment, i.e. with several different electromagnetic field (EMF) sources and scattering problems, require an accurate analysis of problems concerning narrowband measurements. The aim of the present work was the development of an automatic procedure for narrowband electric field measurements in open sites with multiple sources, in order to perform accurate and reproducible measurements. Results regarding measurements carried out in a suburban site are reported.
Subject(s)
Electromagnetic Fields , Environmental Exposure/analysis , Radiation Monitoring/methods , Automation , Environmental Pollution , Humans , Radio WavesABSTRACT
International guidelines. ICNIRP, and proposed standards. IEEE-ANSI, define basic restrictions in terms of rate of power absorbed for mass unit (SAR) for localised exposure of electromagnetic fields such as in the near field region of cellular phones. Compliance tests of cellular phones consist in checking that emitted power from mobile telecommunication equipment (MTE) is below the reference levels and they are performed by assessing the absorbed power in specific head phantoms. The outcome of this work is the description of experimental procedures for evaluating SAR induced into the head by localised exposure. The set up instituted for compliance testing of MTE is described with the different components: dielectric simulators, electric field sensors. scanning system, remote control and data recording. Calibration procedures of E sensors and uncertainty evaluation of measures are presented. Finally the results of a comparison among a few European laboratories and of a test of some hand-set devices are shown.
