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International Journal of Research in Wireless Systems, Volume 1, Issue 2, December (2012) Biological Effects and Health Risks Related to Mobile Communication Raad .H.Thaher Assistant Professor, Ministry of Higher Education and Research, Baghdad, Iraq E-mail: [email protected] major public health consequences. The output power from the digital mobile phones antennae is Abstract: The effect of mobile communication can be understood as biological effect (normal situation). However when this effect exceeds a certain limit such that the temperature of the body increases, it then poses a health hazard. Further, the effects of extremely low frequency radiation (elf EM) and radio frequency (RF) are described. The non-thermal and thermal effects of RF radiation are explained with the guidelines and recommendations being presented. It is concluded that o the rise of 1 c in the body temperature will cause a change in the body behavior. The minimum safety distance for different mobile models is calculated and the minimum distance from mobile station is also calculated for safety purposes. Key Words: RF radiation, Biological effect, safety exposure distance I.INTRODUCTION Microwaves are a specific category of radio waves that can be defined as radio frequency radiation where frequencies range from several hundred megahertz (MHz) to several gigahertz (GHz). One of the most familiar and widespread uses of microwave energy is found in household microwave ovens, which operate at a frequency of 2450 MHz (2.5 GHz). Concerns about exposure to RF fields from sources used for mobile telecommunications, radars, radio and television broadcast, medical and industrial applications are very much prevalent. Most of these concerns arise because new technologies are introduced. Meanwhile mobile phone usage has increased dramatically with falling costs. Industrial sources suggested that there would be over one billion users by 2007, far exceeding telephone usage via fixed-lines. A thought provoking question is if any adverse health effect is established from usage of mobile phones, will it be a global concern? This is a pertinent question as developing countries are putting a greater effort and investment to establish this technology as against fixed telephone systems. Thus, even a small impact on health could have www.ijrws.org much lower than the older analogue models. However, RF emissions from the base stations that communicate between mobile phones and the workers have a smaller order of magnitude than the handsets. We will describe the effect of extremely elf EMF and the RF EMF. II. RF EM radiation At RF, any heating concerns that arise could be put down to the electric field of microwaves. In the modern world, with the use of sophisticated microwave emitting devices for communication in the air surveillance system, industry, diagnostic and therapeutic purposes in medicine-the importance of electromagnetic pollution is not over emphasized. Microwave communication equipments are in use in key defense and commercial networking systems. One of the primary responsibilities of any organization is to safeguard its personnel like radar workers and the personnel involved with high power equipment manufacture which entails working near the field of microwave generating sources. From the radar worker in a defense related scenarios to a housewife using a microwave oven – all of them are exposed to the potential hazards. The sources of microwave and RF radiation are: air traffic control systems, police and military radar, earth to satellite broad cast television systems, long distance telephone equipment, medical diathermy devices, cancer diagnostic & therapeutic (Hyperthermia) equipment, microwave ovens, industrial applications and microwave generators. There are many reports in the literature [1], [2], [3], [4] indicating adverse health effects of electromagnetic radiation emitted from cell phones with 50% of their energy being deposited when held close to the head. Hence there is a significant need 29 International Journal of Research in Wireless Systems, Volume 1, Issue 2, December (2012) to explore the biological effects of electromagnetic radiation in different frequency ranges. III.Fields from mobile Phone Systems A. Output from Mobile Phone The RF power from a phone is transmitted by the antenna together with circuit elements inside the handset. The antenna is usually a metal helix or a metal rod a few centimeters long extending from the top of the phone. Neither type is strongly directional, although more power is radiated in some directions than others. It was found that at points 2.2 cm from an antenna (the distance at which calculations were made), the maximum values of the electric field are calculated to be about 400v/m for 2w, 900 MHz phone and about 200v/m for 1w, 1800MHz phone and the maximum magnetic field is calculated to be about 1µT for both phones. When the antenna is near the body, the radiation penetrates it but the magnetic field is particularly weaker than what it was outside. However the received power at any point from the mobile phone can be calculated from the equation 2 Pd =Pt /(4πd ) (1) Where Pt: The total radiated power from the mobile phone, Pd: The power density at any distance (d) from the mobile phone. Figure (1) shows the power density (mw/cm2) and minimum safety exposure distance from the mobile phone for different groups of mobile models. The head of the user is in the field of the radiation pattern of mobile antenna and for short antennas, the outer boundary exist at a distance (D) from the antenna surface where [9] D= λ/ 2π (2) And the mobile phones operate at frequencies from 900 MHz to 1800MHz which means that the values of D will be in the range (2.6-5.3 cm). The minimum 2 safety exposure power density is 0.4mw/cm . The minimum safety exposure distance for each mobile model is calculated (using equation (1)) and presented in table (1). B. Output from Base Stations The base station antennae transmit appreciably greater power than phones. The limit of the power is formally set by the need to avoid RF interference and defined by a license issued by the Radio Communications Agency. This does not directly limit the total power emitted but instead fixes the maximum intensity that an antenna can transmit into the main beam. This is done by defining the maximum “equivalent isotropically radiated power “(EIRP) that can be transmitted. The EIRP is the power that would have to be emitted equally in all directions to produce a particular intensity. In fact, the antennas used are very far from Isotropic, with most of the power being emitted into the main beam, and the ratio of the EIRP to the total power output is called the gain of the antenna .For a 120 sector antenna the gain is usually between about 40 and 60. The maximum size of the electric fields resulting from base stations to which the general public is exposed is around 5v/m, although the largest field measured to date by is 2V/m .However the minimum distance from the base station antenna (in terms of the base station transmitted power) can be calculated as follows: Let there are N transmitter with M watt each, therefore the maximum power is Pmax =10 log (M*N) Db The total losses in combiners between transmitters, connectors and cables are about 9dB. Therefore the maximum input power to the antenna is Y= Pmax - 9dB (4) If the antenna gain is Z dB, then the effective Isotropic power (EIRP) in the direction of the main lobe is EIRP = Y+Z dB or EIRP=10 (Y+Z)/10 W (5) Notice that in other directions (not in the main lobe directions) the EIRP is less 10 dB than the main lobe (i.e. EIRP = EIRPmain-10dB), the minimum safety distance from the base station (taking into account the minimum safety power density 0.4mw/cm2) is -3 1/2 Dmin = (EIRP(w)/4 π*4*10 ) www.ijrws.org (3) (6) 30 International Journal of Research in Wireless Systems, Volume 1, Issue 2, December (2012) As a practical example if there are four transmitters with 60 w each, then the maximum power is Pmax =10 log (4*60) =23.8 Db. The maximum input power to the antenna is Y=23.89 =14.8 dB. If the antenna gain is about 16 in the main lobe direction, therefore EIRP = 14.8+16 =30.8 dB =1202.26 w After taking into account the minimum safety power 2 density as 0.4mw/cm , it can be showed that -3 1/2 Dmin =(1202.26/4 π**4*10 ) =4.89 m This means that one must be at a distance not less than 4.89 m from the base station, otherwise the effect may occur. This distance will increase with the number of transmitters and power. Figure (2) shows the relation between the transmitted power (EIRP) and the minimum safety distance required from the base station. IV. Mechanisms of interaction RF fields induces torques on molecules that can result in displacement of ions from unperturbed positions, vibrations in bound charges (both electrons and ions), and rotation and reorientation of dipolar molecules such as water. These mechanisms, described by classical electrodynamics theory, are not capable of producing observable effects from exposure to low level RF fields, because they are overwhelmed by random thermal agitation. Moreover, the response time of the system must be fast enough to allow it to act within the period of interaction. Both considerations imply that there should be a threshold (below which no observable response occurs) and a cut-off frequency (above which no response is observed). These thresholds are expected to be present in more refined models if they correctly account for thermal noise and kinetics of the system. Exposure to EMF at frequencies above about 100 kHz can lead to energy and temperature increases. Thus on a general note, exposure to uniform (plane wave) EMF results in a highly nonuniform deposition and distribution of energy within the body. This must be assessed by dosimetric measurement and calculation. For absorption of energy by the human body, EMF can be divided into four ranges: www.ijrws.org About 100 kHz to less than about 20MHz, where absorption in the trunk decreases rapidly with decreasing frequency and significant absorption may occur in the neck and legs. From about 20 MHz to 300 MHz, at which relatively high absorption can occur in the whole body and even higher values if partial body (e.g. head) resonances are considered. From about 300 MHz to several GHz, at which significant local uniform absorption occurs. Above about 10 GHz, at which energy absorption occurs primarily at the body surface. In tissue, the specific absorption rate (SAR) of RF energy absorbed per unit mass is proportional to the square of the internal electric field strength. The average SAR and SAR distribution can be computed or estimated from laboratory measurements. The localized SAR is calculated as follows: 2 SAR= БE /ρ (7) Where: Б(S/m): is the electrical conductivity of the tissue E(V/m): is the measured internal electric field strength and 3 ρ(Kg/m ): is the mass density of the tissue. The recommended value of SAR is 0.4 w/kg. Values of SAR depend on the following factors: The incident field parameters, i.e. the frequency, intensity, polarization, and sourceobject configuration (near field or far field). The characteristic of the exposed body, i.e its size, internal and external geometry, and the dielectric properties of the various tissues. Reflection, absorption and scattering effects associated with the ground or other objects in the field near the exposed body. V. Biological effects of exposure to RF fields Mobile telephony is based on radio communication between a portable handset and the nearest base station. Every base station serves as a ”cell” varying in radius from hundreds of meters in densely populated areas to kilometers in rural areas, and is connected both to the conventional landline telephone network. As the mobile phone user moves from cell-to-cell, the call is transferred from one base station to the next without interruption. The radio communication depends on microwaves at 31 International Journal of Research in Wireless Systems, Volume 1, Issue 2, December (2012) 900 or 1800 MHz to carry voice information via small modulations of the wave’s frequency. A base station antenna typically radiates 60w and a handset between 1 and 2w (peak).The antenna of a hand set radiates equally in all directions, but the base-station produces a beam that is more directional. A. Non Thermal effects Microwaves have a range of non-thermal effects shown below: i. In Vitro Studies Reports from in vitro research indicate that low level RF fields may alter membrane structural and functional properties that trigger cellular responses. It has been hypothesized that the cell membrane may be susceptible to low-level RF fields, especially when these fields are amplitude modulated at low frequencies. Although, at higher frequencies lowlevel RF fields do not induce significant changes to the membrane structure and functions, they can penetrate the cell membrane and possibly influence cytoplasm structure and function. These RF field induced alterations, if they occur, could be anticipated to cause a wide variety of physiological changes in living cells which are currently poorly understood. A lack of RF exposure effects on mutation frequency has been reported in a number of test samples including yeast and mouse lymphoid cells. No effect of RF field exposure on chromosome aberration frequency in human cell has been confirmed yet. ii. In Vivo Studies[6],[7] Several studies indicate that RF fields may affect DNA directly. Exposure to mobile phone radiation also decreases the preparatory slow potentials in certain regions of the brain and affects memory tasks, blood pressure was found to increase during exposure to radio frequencies. VI. Guidelines and Recommendations A. Sources of Exposure General population is susceptible to whole body exposure from base station emissions, but their intensity is less than handset emissions. Base stations communicate with mobile phones with a defined area or “cell’. This can be of three types: macro cells, micro cells and pico cells depending www.ijrws.org upon their size and the power output of the antenna. Macro-cells provide the main structure for the base station network. The base stations for macro cells have power outputs of tens of watts and communicate with phones up to about 35 kilometers distance. There are concerns, nevertheless, if the emissions from all base stations are uniformly low, if they could cause unknown health effects, and if their output will rise with increased use of mobile telecommunications. Micro-cells are used to infill and improve the main network, especially where the volume of calls is high. They are situated in places such as airports, railway stations and shopping malls. Their number is rapidly increasing in line with the growth in demand for mobile phones. The micro cell base stations emit less power than macro cells and their range is a few hundred meters. We understand that exposures above guidelines do not occur, provided the case surrounding the antenna is kept in place. Pico-cell base stations have a lower power output than those of microcells (a few watts) and are generally situated inside buildings. It is likely that the number of pico-cells within buildings will substantially increase. We are satisfied that their emissions would not exceed the guidelines. B. Current Guidelines on Acceptable Levels of Exposure to Radiofrequency Radiation In 1998 the international Commission on NonIonizing Radiation Protection (ICNIRP) published its own guidelines covering exposure to RF radiation. These were based on essentially the same evidence used by NRPB for workers on the limits of exposure (100mwlcm2). However, under the ICNIRP guidelines, the maximum levels of exposure of the public are about five times less than those recommended for workers. The reason for this approach was the possibility that some members of the general public might be particularly sensitive to RF radiation. However, no detailed scientific evidence was provided that justifies this additional safety factor. Both the NRPB and ICNIRP guidelines are based on the need to avoid known adverse health effects. At the time these guidelines were drawn up, the only established adverse effects were those caused by the heating of the tissues. 32 International Journal of Research in Wireless Systems, Volume 1, Issue 2, December (2012) VII. Conclusion The effect and health risk of mobile communication was explained and it was concluded that the effect consists of non-thermal and thermal effects, the thermal effect being more effective. It was concluded that the effects depend upon two main factors, power and time. Therefore, the biological effect exists in all cases but when this effect exceeds a certain threshold limit it becomes a health hazard. A health hazard is a biological effect outside the normal range of physiological compensation, and with the increase in core temperature of 1oc or more, this can lead to changes in the performance of well-learned tasks and other simple behaviors. It is recommended to keep mobile phones away from children because it affects their nervous system and usage of mobile telephones must be restricted to lesser period of time only and for only essential purposes, with low SAR values and with hands-free devices that have been proved to reduce SAR exposure. Motorists should be strongly discouraged from using mobile phones while driving to overcome the risk of traffic accidents. Also the safety exposure distance from mobile phones is measured for each mobile model because different mobile phones have different output power and it is recommended to use mobile phones model with less output power. The safety distance from mobile station is measured and for practical purposes (i.e. 60w antenna) the safety distance from the mobile station is 4.501 m and this distance increases with increasing the output power of a mobile station. [6] M.H.Repacholi.”Health risks from the use of mobile phones “, Toxicology letters, Vol.120, pp323-331. 2001 [7] Lin,J.C,”Update of IEEE radio frequency exposure guidelines “,Microwave Magazine,Vol.7Issue 2 ,pp2428 ,April 2006. [8] Who,Who,s agenda for EMF research ,Report WHO/EHG/98.13.World health organization ,Geneva Health; Mobile phones and their base stations, World Health organization ,Geneva,1998. [9] Kraus,J.D, "Antennas", McGraw Hill ,New York,1988 . 7. References [1] Schwan, H.P.,”Interaction of microwave and radio Frequency radiation with biological systems”, IEEE trans. On Microwave theory and Tech. Vol NTT-19, pp146-150, 1971. [2] Igr Belyaev, ”Non-Thermalbiological effect of microwaves”, Microwaves Review, Nov.2005, pp 1329. [3] Henry Lai, ”Neurological effects of radiofrequency electromagnetic radiation relating to wireless communication technology”, IBC-UK Conference ,Sept16-17 ,1997 ,Brussels ,Belgium . [4] “The possible harmful biological effects of low-level electromagnetic fields of frequencies up to 300 GHz”, IET Position statement –May 2006 . [5] Lai, H.,Singh,N.P., ,”Single and double –strand DNA breaks in rat brain cells after acute exposure to radio frequency electromagnetic radiation”,Int.J.Radiat.Bio.69.pp513.1995 www.ijrws.org Table(1) Different mobile models & their Safety exposure distance 33 International Journal of Research in Wireless Systems, Volume 1, Issue 2, December (2012) Figure (1) The power density and distance from the mobile phone for different mobile models Mr. Thaher was born on September 1955. He got his B.Sc and the M.Sc degree from the Department of Electrical Engineering, College of Engineering, University of Baghdad in 1978 and 1981 respectively. He got the Ph.D degree in Electronic and Communication Engineering from the Polytechnic University of Bucharest, Romania in 1997. Mr. Thaher is currently working as an assistant professor in the Department of Electrical Engineering, College of Engineering, Al Mustansiryah University, Iraq. He has published research papers both on national and international level. His research interests include, topics such Mobile communication, Microwave Engineering, Communication networks, DSP ,and Medical Instrumentation . Curve(1…Pt=1.5w) for models (Bosch GSM908,Philips Genic 900,Ericsson Lx588). Curve(2….Pt=1.19w) for models (Nokia6120,Siemens C-35,Nokia3120). Curve(3….Pt=1w) for models (Siemens S35,Motorolla timeport,Philliphs Diga). Curve(4…..Pt=0.85w) for models(EricssonSH888,Nokia6110,Motorolla di60). Curve(5…..Pt=0.72w)for models(Nokia 8219,Simens C-25,Motorolla CD930). Curve(6……Pt=0.22w) for models(Nokia 8810,Ericsson GH628,Nokia 8850) Figure(2) The effective Isotropic Radiated power (EIRP) and minimum safety exposure distance from mobile station. www.ijrws.org 34