Non-ionizing electromagnetic radiation monitoring in Greece

Transcription

1 Non-ionizing electromagnetic radiation monitoring in Greece Antonis Gotsis, Nikolaos Papanikolaou, Dimitris Komnakos, Agamenon Yalofas, and Dr Philip Constantinou Mobile Radio-Communications Laboratory, School of Electrical and Computer Engineering, National Technical University of Athens, Greece, 9 Heroon Polytechneiou Street (tel: ; fax: ; {gotsis,npapan,dkomna,yalofas,fkonst}@mobilentuagr) The design, development and operation of a network for the monitoring of the nonionizing electromagnetic radiation in Greece is presented in this paper Two independent sub-networks, called Hermes and pedion24 have been operating since November 2002 in several areas, and more than 4,000,000 electric field strength measurements have been conducted to date The measurement results indicate that the non-ionizing electromagnetic radiation levels are several times below the European Commission Recommendation 1999/519/EC and the Hellenic Republic Law no3431 reference levels 1 Introduction During the last decade, the installation and operation of several wireless networks, such as the GSM, UMTS, TETRA and Wi-Fi systems has led to increasing public concern about the exposure to electromagnetic (EM) radiation emitted by such sources In conjunction with traditional broadcasting systems (FM Radio and VHF- UHF Television), RADAR systems etc these concerns call for the continuous information of the public regarding their exposure to EM radiation levels On site, ad-hoc measurements are the first step for estimating the exposure levels Nevertheless, ad-hoc measurements refer to a specific time period (usually 1-2 hours) On the other hand the notion of continuous measurement of EM radiation levels on a 24-hour basis is more appealing to the concerned public This is due to the fact that the recorded values can be directly compared to the public exposure safety values, called reference levels, which are set by the relevant organizations, such as the EC [1] and local governmental authorities [2] Therefore, a network for the measurement and recording of non-ionizing Electromagnetic Radiation levels on several sites and on a 24-hour basis is one of the best solutions for keeping the public informed Another important parameter of such a network is to present the results of the measurements to the public via a user-friendly web site Monitoring networks are a valuable tool in attempting to deal with public concerns about the potential health effects of non-ionizing electromagnetic radiation As a result, several monitoring systems are implemented all over Europe and Africa (Italy, Spain, Portugal, United Kingdom, Malta, and Egypt) [3] - [6] Moreover network deployment entails a number of challenges, in terms of hardware certification, network control and daily maintenance With all the above considerations in mind two Electromagnetic Radiation (EMR) monitoring networks have been deployed in Greece Hermes network [7] started its operation on

2 November 2002, while pedion24 [8] (where pedion is the Greek word for field) on November 2005 So far 46 continuous monitoring stations have been installed in urban and rural areas of Greece and more than 4,000,000 measurements have been conducted and stored Moreover there is a plan for further expansion during the next years The paper is structured as follows: In Section II we present the design aspects of such a monitoring network, regarding the hardware and the software Section III gives a brief description of the two monitoring networks operating in Greece and Section IV presents overall measurement results conducted by the two networks to date In Section V we draw some conclusions with relation to the measurement results and conclude our work 2 System Architecture Design Aspects A typical system architecture of a centralized monitoring network is depicted in Figure 1 The network consists of the remote measurement stations (RMSs) and one or more control unit(s) (CU(s)) Each RMS communicates with the CU via a public wireless network such as GSM, GPRS or UMTS Such a wireless interface allows the installation of a measurement station practically everywhere as long as the area is covered by any cellular operator The CU controls the remote units, stores the measurement data and hosts the web site Any interested party can access the results through an Internet gateway A detailed description of each part of the system follows RMS CU User PC RMS GSM/GPRS/UMTS Network Internet RMS CU User PC Figure 1: System Architecture 21 Remote Measurement Stations The Measuring Equipment must be a fully autonomous unit which is able to: (a) operate continuously (on a 24-hour basis), (b) perform Electromagnetic Radiation measurements in the frequency range of interest covering the main sources that contribute to the total electromagnetic pollution, (c) store the measurements in its internal memory and transmit them to the Control Unit via a wireless interface for further elaboration, (d) supplied either by the main power supply or a solar panel (preferable), (e) be fully remotely controlled, which means that after its installation no human presence is needed on site and (f) detect abnormal operation of any kind (self diagnostics such as power loss and overheating problems) and report it to the CUs In order to fulfill these requirements, a remote monitoring station would consist

3 of a broadband isotropic and triaxial electric field sensor, a module containing the necessary electronics, a GSM/GPRS/UMTS modem, as well as temperature and humidity sensors A major problem encountered in this system is the periodic calibration of the monitoring stations Regarding the measurement quantities, either broadband or narrow-band measurements can be conducted Broadband Measuring Stations record the Electric Field Strength and/or the Power Flux Density for a given frequency range A range of 100 KHz - 3 GHz is usually enough in order to take into account the vast majority of the sources Other possible ranges are for example MHz (the GSM900 band), MHz (GSM-1800 plus UMTS band), etc In [9] - [11] the interested reader can find a plethora of commercially available monitoring units Recently, selective monitoring systems became commercially available [12] The referred stations are fully autonomous and can be remotely controlled via the GSM/GPRS protocol 22 Control Unit(s) The Control Unit is a Server computer equipped with a wireless modem and the necessary software applications for (a) controlling the remote monitoring stations and configuring the operational parameters, (b) downloading the measurement data via the wireless interface, (c) storing the data in its hard disk and (d) processing the measurement results and publishing them to the corresponding web site Usually the RMS manufacturer provides a software application for the control of the units and the data collection Through this application the system administrator is able to change the measurement and communication parameters The data is collected and exported in formatted text files (csv files) The measurement data is stored in a database therefore a full historical record for every measurement site is kept on the CU An administrative tool (desktop- or web-based) is developed in order to perform the above operations Finally a Web Server running on the CU hosts the web site A more detailed description of the hardware and software architecture can be found in [13] [16] 3 Operating Networks in Greece Two EMR monitoring networks have been deployed in Greece These networks share a common scientific goal, that is, to conduct accurate, long-term, continuous measurements of the non-ionizing electromagnetic radiation in our country and to determine and understand trends and variability of the field values 31 Hermes Monitoring Network In November 2002, Mobile Radio-Communications Laboratory (MRCL) of the National Technical University of Athens, commenced the operation of the first EMR monitoring network in Greece, named Hermes The formation of this network was motivated by the lack of previous systematic measurement and recording of EM field strength levels over the country and aimed at providing valid, up-to-date information to citizens about the results of these measurements, namely, the level of exposure to non-ionizing EM radiation The system at its present state (January 2007) comprises 37 remote monitoring stations spread all over Greece and two control units located in two University laboratories (National Technical University of Athens NTUA and Aristotle University of Thessaloniki AUTH) MRCL controls stations located on the southern part of Greece, while the AUTH Laboratory the northern part The stations are located at schools, universities, public authorities

4 buildings and private flats From now on, we will only refer to the stations that are under the control of the Mobile Radio-Communications Laboratory (21 active and 4 inactive stations) The measurement results are open to the public through a devoted web site The web site contains both static and dynamic pages and aims at presenting the measurement results for all the monitored sites It also provides thorough information concerning the non-ionizing electromagnetic radiation exposure issue Through the web site the visitor may view graphs of the measured values for custom date/time interval selection Furthermore, a comparison of the measured values with the Greek legislation reference levels is presented A feedback form is also available to the public in order for them to express questions or comments to the system administrators Although the electric field strength is recorded by the RMSs, Power Flux Density values are presented on the web site 32 pedion24 Monitoring Network In November 2005 Mobile Radio-Communications Laboratory started the operation of a second monitoring network, named pedion24 network The design and operating principles of this network are similar to those of Hermes pedion24 network at its present state (January 2007) consists of 21 remote monitoring stations Locations of monitoring stations are carefully chosen to cover places of special interest such as schools, hospitals, nurseries, areas with high population density and also private flats in Attica and five other prefectures of Greece The network is continuously expanded throughout Greece Detailed description of the networks and the results can be found in [7] and [8] 4 Overall results from the continuous monitoring stations Broadband measurements for the band 100 khz 3GHz Until December ,175,000 6-minutes average values of the Electric Field Strength measured on 46 different sites have been accumulated in the databases of the two measurement networks The number of the recorded values, the mean value ( E ) and the standard deviation per site (σ) of the measured values for both networks are shown in Table 1 Electric Field Strength (V/m) Measurement Site Number of records E σ PEDION24 STATION 1 43, PEDION24 STATION 2 72, PEDION24 STATION 3 56, PEDION24 STATION 4 55, PEDION24 STATION 5 50, PEDION24 STATION 6 50, PEDION24 STATION 7 29, PEDION24 STATION 8 23, PEDION24 STATION 9 10, PEDION24 STATION 10 24, PEDION24 STATION 11 51, PEDION24 STATION 12 33,

5 PEDION24 STATION PEDION24 STATION 14 51, PEDION24 STATION 15 43, PEDION24 STATION 16 16, PEDION24 STATION 17 7, PEDION24 STATION 18 7, PEDION24 STATION 19 6, PEDION24 STATION 20 8, PEDION24 STATION 21 7, HERMES STATION 1 77, HERMES STATION 2 77, HERMES STATION 3 72, HERMES STATION 4 322, HERMES STATION 5 309, HERMES STATION 6 225, HERMES STATION 7 265, HERMES STATION 8 263, HERMES STATION 9 252, HERMES STATION , HERMES STATION , HERMES STATION 12 93, HERMES STATION 13 13, HERMES STATION 14 18, HERMES STATION 15 3, HERMES STATION 16 1, HERMES STATION , HERMES STATION , HERMES STATION 19 90, HERMES STATION , HERMES STATION , HERMES STATION , HERMES STATION 23 71, HERMES STATION 24 26, HERMES STATION 25 34, Table 1: Overall Measurement Results for the period 11/ /2006 A sample time graph of the 6-minutes average value of the electric field strength dynamically created on the web site of pedion24 project is shown in Figure 2 The specific diagram depicts the electric field strength levels concerning one RMS for a time period of one week Two safety reference levels are also shownthe specific values correspond to the strictest reference levels in the FM and GSM bands [2] In Figure 3, the electric field strength probability density function and a gaussian fitting curve are illustrated

6 Figure 2: A sample graph of the 6-min average recorded electric field strength versus time 0,12 Electric field histogram Gaussian fitting 0,10 Probability Density 0,08 0,06 0,04 0,02 0,00 Electric Field Strength (V/m) Figure 3: A mean field strength distribution and Gaussian Fitting PDF for all measurements Broadband Measurements per band (100 KHz 900 MHz, 900 MHz 3 GHz) The measurement stations have the ability to measure the electric field strength for two narrower bands, namely 100 KHz 900 MHz and 900MHz 3GHz The resulting histogram (pdf) is shown in Figure 4 Observing the specific diagram it can be seen that for electric field values below 14V/m the probability density for 100kHz 900MHz band is greater than the probability density for 900MHz 3GHz band On the contrary for electric field values above 14 V/m the greater probability density is that for 900MHz - 3GHz band, which contains services like GSM 900 (downlink), DCS 1800 and UMTS This can be explained by the fact that the remote

7 measurement stations are installed in sites near GSM, DCS and UMTS base stations Comparison of the results with the reference levels A comparison of the mean measured Electric Field Strength per station with the strictest reference level in the band 100 KHz 3 GHz (which is 217 V/m [2]), is presented in Figure 5 Actually, we depict the inverse of the ratio of the measured value to the reference level, which expresses how many times below limits are the measured field values The accumulated measurement results are in average 46 times below the above reference value 0,14 0,12 0,1 Probability Density 0,08 0,06 0,04 0,02 0 0,2-0,4 0,4-0,6 0,6-0,8 0, ,2 1,2-1,4 1,4-1,6 1,6-1,8 1, ,2 2,2-2,4 2,4-2,6 2,6-2,8 2, ,2 3,2-3,4 3,4-3,6 3,6-3,8 3, ,2 4,2-4,4 4,4-4,6 4,6-4,8 Electric Field Strength (V/m) 100kHz-900MHz 900MHz-3GHz Figure 4: Field Strength Distribution Probability per band 1,00 Times below the reference levels 10,00 100, ,00 Measurement stations Figure 5: Comparison of monitored field strength to the reference levels

8 5 Discussion Conclusions Two automated nationwide monitoring networks of the electric field strength covering the RF spectrum were presented More than 4,000,000 E-field strength values have been recorded in the databases of these projects during the last years The results of the measurements were drawn for the whole band (100 KHz - 3 GHz), as well as for the lower (100 KHz 900 MHz) and the higher (900 MHz - 3 GHz) part of the band Since the commencement of operation the measured EM Radiation levels are significantly below the safety reference levels Specifically, 90% of the stations have been measuring electric field strength values below 3 V/m The variation of the electric field on each site is negligible for the majority of the stations, while the measured E-field depends on the relative position between the site and the antennas The most important emission sources are FM, TV and mobile telephony antennas, at least at urban and suburban areas A thorough examination of non-ionizing EMF radiation in dense urban and rural environments is of utmost importance We are currently planning the installation of more remote stations in these kinds of environments More emphasis will be given in the measurement and evaluation of the exposure levels in the proximity of mobile telephony base stations References [1] European Commission (EC), Council Recommendation 1999/519/EC of 12 July 1999 on the limitation of exposure of the general public to electromagnetic fields (0 Hz to 300 GHz), Off J Eur Comm, L 199, 59, 30 July 1999 [2] Hellenic Republic Law No 3431, About Electronic Communications and other Provisions, Government Gazette, FEK No 13 A / [3] monit Project : Electromagnetic Radiation Monitoring in Mobile Communications [4] Cassiopea Project : [5] Progett Gardjola : [6] Project Horus : [7] Hermes project: A Project for Systematic Measurements of the Electromagnetic Radiation, [8] pedion24 project : A Project for Continuous Measurements of the Electromagnetic Radiation, [9] Narda Area Monitor System 2600, Narda Safety Test Solutions : [10] PMM 8055S Electric and Magnetic Field Monitoring Station, PMM Safety Products, [11] EE4070, EE4070S,MCE Monitoring System, EIT srl, [12] Antennessa EMF Measurement Systems : [13] A Yalofas, A Gotsis, C Veranopoulos, P Constantinou, G Belesiotis, M Petkaris, N Babalis, A Fully Automated and Geographically Distributed Network for the Continuous Measurement of the RF Radiation Hermes Project, TELSICS, IEEE 6th International Conference on Telecommunications in Modern Satellite, Cable and Broadcasting Services, Niš, Yugoslavia, October 2003 [14] A Gotsis, A Yalofas, C Veranopoulos, P Constantinou, Design and Development of an Automated Web Controlled Measurement Network for the RF Field Strength Monitoring, IEEE Region 8 EUROCON, The International Conference on Computer as a Tool, Ljubljana, Slovenia, September [15] A Gotsis, A Yalofas, P Constantinou, A Boursianis, T Ganatsos, N Tachas, T Samaras, T Daskalou, M Petkaris, Installation and Operation of an EM Radiation Monitoring Network In Greece, 3rd International Workshop on Biological Effects of Electromagnetic Fields, Kos, Greece, October 2004 [16] D Komnakos, A Gotsis et al, Design, development and operation of an electromagnetic radiation monitoring network in Greece: Hermes project, 4th International Workshop on Biological Effects of Electromagnetic Fields, Crete, Greece, October 2006