Browsing by Author "Jokela, Kari"
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- ItemAssessment of the magnetic field exposure due to the battery current of digital mobile phones.(2003-12-25) Jokela, Kari; Puranen, Lauri; Sihvonen, Ari-PekkaHand held digital mobile phones generate pulsed magnetic fields associated with the battery current The peak value and the waveform of the battery current were measured for seven different models of digital mobile phones and the results were applied to compute approximately the magnetic flux density and induced currents in the phone user s head A simple circular loop model was used for the magnetic field source and a homogeneous sphere consisting of average brain tissue equivalent material simulated the head The broadband magnetic flux density and the maximal induced current density were compared with the guidelines of ICNIRP using two various approaches In the first approach the relative exposure was determined separately at each frequency and the exposure ratios were summed to obtain the total exposure multiple frequency rule In the second approach the waveform was weighted in the time domain with a simple low pass RC filter and the peak value was divided by a peak limit both derived from the guidelines weighted peak approach With the maximum transmitting power 2 W the measured peak current varied from 1 to 2 7 A The ICNIRP exposure ratio based on the current density varied from 0 04 to 0 14 for the weighted peak approach and from 0 08 to 0 27 for the multiple frequency rule The latter values are considerably greater than the corresponding exposure ratios 0 005 min to 0 013 max obtained by applying the evaluation based on frequency components presented by the new IEEE standard Hence the exposure does not seem to exceed the guidelines The computed peak magnetic flux density exceeded substantially the derived peak reference level of ICNIRP but it should be noted that in a near field exposure the external field strengths are not valid indicators of exposure Currently no biological data exist to give a reason for concern about the health effects of magnetic field pulses from mobile phones
- Item[Mobile phones radiate--risk to the health?].(2011-10-14) Jokela, Kari; Auvinen, Anssi; Hämäläinen, HeikkiThe mobile phones radiate electromagnetic energy which is partly absorbed into the tissues in the vicinity of the phone The minor heating in maximum up to 0 3 degrees C may cause some alterations in the expression of genes and proteins similar to physiological response to other stimuli Biophysical studies at the cellular and molecular level have not revealed any well established interaction mechanism through which mobile phone radiation could induce toxic effects below the thermal effect level Research results on various biological effects in vitro and in vivo are continuously published but there is no consistent evidence on well established harmful effects The mobile phone radiation is not carcinogenic for experimental animals or genotoxic for cells According to epidemiological studies and psychophysiological brain function studies the use of mobile phones does not seem to increase the risk of tumors in the head and brain or disturb the function of central nervous system However there is a need for more research on the long term effects of mobile phone radiation particularly on children
- ItemSpecific absorption rate and electric field measurements in the near field of six mobile phone base station antennas.(2009-04-08) Toivonen, Tommi; Toivo, Tim; Puranen, Lauri; Jokela, KariIn this article the exposure to radio frequency electromagnetic fields was studied in close proximity distances of 10 100 300 and 600 mm to six base station antennas The specific absorption rate SAR in 800 mm x 500 mm x 200 mm box phantom as well as unperturbed electric field E in air was measured The results were used to determine whether the measurement of local maximum of unperturbed electric field can be used as a compliance check for local exposure Also the conservativeness of this assessment method compared to the ICNIRP basic restriction was studied Moreover the assessment of whole body exposure was discussed and the distance ranges presented in which the ICNIRP limit for local exposure could be exceeded before the limit for whole body SAR These results show that the electric field measurement alone can be used for easy compliance check for the local exposure at all distances and for all antenna types studied However in some cases when the local peak value of E was compared directly to the ICNIRP reference level for unperturbed E the exposure was overestimated only very slightly by factor 1 1 compared to the basic restriction for localized SAR in a human and hence these results can not be generalized to all antenna types Moreover it was shown that the limit for localized exposure could be exceeded before the limit for the whole body average SAR if the distance to the antenna was less than 240 mm