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D. Bernatavičius et al. / Medical Physics in the Baltic States 7 (2009) 102 - 105 assess whether radiofrequency radiation exposure from mobile phones is associated with tumour risk, specifically, risk of glioma, meningioma, acoustic neuroma and parotid gland tumours. [2] Despite the fact that the study has been started in year 2004 collective INTERPHONE results are not published yet. Researches claim that using a mobile phone for ≥10 years approximately doubles the risk of being diagnosed with a brain tumour on the same side of the head as that preferred for cell phone use. [4] 2. Experimental Measurements of field strength were performed using portable wide band electric field meter Chauvin Arnoux C.A 43. (Table 2). Table 2. Main specifications of field meter Bandwidth Electric field 100 kHz 0,1 V/m to 2,5 GHz to 200 V/m Measurement’s location and distances from the transmitter tower were identified using GPS navigation system Acme NS-351. Mobile phone Nokia 6500c was used in all measurements. Measurements were performed for four mobile phone modes in each location, indicated in Fig.1. These modes were: 1.swich on; 2.dialling and calling; 3.ringing and answering; 4.sending SMS. Considering the fact that there is a natural background of electromagnetic radiation, it was not necessary to measure electric field for a long time. The first and the fourth modes required up to 10 seconds for one measurement, however the second ant the third modes required up to 30 seconds for one measurement. Fig. 1. Locations of measurement points All measurements were performed holding the phone at a distance of ~20 cm to antenna of field meter. This distance is about the same as diameter of human head. Locations of measurements were selected along the road 5 to 10 meters outside from the road and were 103 marked on the map. Locations outside of the road were selected to ensure independency of the experiment on the traffic (It was possible that vehicles are equipped with radio transmitters). 3. Results Collected data was grouped and analysed. Only mostly typical data for different locations are presented in this paper. Only small variations from 1 V/m to 2 V/m. of the background electric field were found during the investigation. Do to this reason, no compensation measures were undertaken. It is easily seen in Fig.2 that the field strength increases during the first second to maximum and then drops down step by step. The curves for switch on and sending SMS are approximately the same, but the curve representing calling-mode is different: it drops down when the conversation starts, but remains higher than the background level until the end of conversation. E, V/m 18 16 14 12 10 8 6 4 2 0 Switching on Calling Sending SMS 0 5 10 15 20 25 t, s Fig. 2. Changes of electric field strength for different modes of phone operation t, s 30 25 20 15 10 5 0 0 5 10 15 d, km Fig. 3. Time span which is needed for drop down of the electric field strength in call mode of phone
D. Bernatavičius et al. / Medical Physics in the Baltic States 7 (2009) 102 - 105 Fig.3 shows time dependence of the signal quality: time span, which is needed to drop down field strength, is bigger when the distance between operating phone and transmitter tower is longer. If the signal quality is high enough, it takes less time to drop down the field strength (Fig.4) E, V/m 30 25 20 15 10 5 0 Bad connection Good connection 0 5 10 15 20 25 30 t, s Fig. 4. The influence of signal quality for calling mode We were trying to get clear relationship between electric field strength and the distance to the transmitter tower. Unfortunately it was not possible because of the influence of other factors like uneven terrain. The trends for different modes of phone operation are presented in Fig. 5-8. E, V/m 35 30 25 20 15 10 5 0 900 1400 1523 1562 1834 2052 2250 3138 4332 5300 6086 6716 7579 8073 9153 9734 10484 13073 d, m Fig. 5. Field strength distribution along the road for a switch on mode 104 E, V/m 35 30 25 20 15 10 5 0 900 1400 1523 1562 1834 2052 2250 3138 4332 5300 6086 6716 7579 8073 9153 9734 10484 13073 d, m Fig. 6. Field strength distribution along the road for a calling mode E, V/m 25 20 15 10 5 0 900 1400 1523 1562 1834 2052 2250 3138 4332 5300 6086 6716 7579 8073 9153 9734 10484 13073 d, m Fig. 7. Field strength distribution along the road for a conversation mode E, V/m 35 30 25 20 15 10 5 0 900 1400 1523 1562 1834 2052 2250 3138 4332 5300 6086 6716 7579 8073 9153 9734 10484 13073 d, m Fig. 8. Field strength distribution along the road for a sending SMS mode. 4. Conclusions Radiated electromagnetic waves are most intensive at the beginning of the connection. Then intensity decreases gradually to certain magnitude, which is only enough to sustain the connection. This settled electric field value might be hardly distinguishable from background radiation if the connection is of good
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2009 PROCEEDINGS OF THE 7 th INTERN
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Executive editor: D.Adlienė CONFER
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11.15-11.30 Daiva Leščiute, Valda
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MEDICAL PHYSICS IN THE BALTIC STATE
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S. Mattsson / Medical Physics in th
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