EXPOSURE INDICES IN RF EPIDEMIOLOGY

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1 EXPOSURE INDICES IN RF EPIDEMIOLOGY Paolo Vecchia National Institute of Health, Rome, Italy

2 Advances in Biological effects and Dosimetry of Low Energy Electromagnetic Fields Erice, 28 March - 8 April 1981

3 Sol Michaelson

4 PROBLEMS IN EXPOSURE ASSESSMENT TWENTY YEARS AGO The available data regarding human exposure to RFR are almost exclusively derived from uncontrolled observations. [ ] In virtually all of the published epidemiological studies and case reports, exposure conditions have been largely undefined or loosely inferred. The most severe limitations upon interpretation of these reports must arise from the fact that actual exposure levels and durations of RFR exposure are unsubstantiated. [ ] the quantitation of occupational exposure is extremely difficult. The latter is particularly true wen the subjects are mobile in the course of their exposure, and are exposed to non-stationary or varied types of fields. N.J. Roberts, Jr. and S.M. Michaelson Epidemiological studies of human exposures to radiofrequency radiation Int Arch Occup Environ Health 56: (1985)

The most severe limitations upon interpretation of these reports must arise from the fact that actual exposure levels and durations of RFR exposure are unsubstantiated.

5 WHAT IS EXPOSURE ASSESSMENT? Precise evaluation of the relevant (biologically effective) quantity at the location of the target organ Which is the biologically effective quantity? Which is the target organ?

6 THE MAIN PROBLEM No dose of electromagnetic fields has been identified Dosimetry is a historical term used to designate a complex of parameters and conditions characterizing the exposure Is an overall quantitation possible (for specific situations)? Exposure index Gradient of exposure

parameters and conditions characterizing the exposure Is an overall

7 BIOLOGICALLY EFFECTIVE QUANTITIES

8 VALIDITY OF SAR SAR is the biologically effective (dosimetric) quantity appropriate for thermal (acute) effects The internal electric field might be a more appropriate candidate However, the two quantities are related by a univocal relationship SAR = E 2 /

electric field might be a more appropriate candidate However,

9 ELF vs RF ELF magnetic fields (Power lines) Geometry simple (simmetric) No shielding RF electromagnetic fields Geometry highly dependent on the source Effective shielding by most materials Possibility of very inhomogeneous exposure

Geometry highly dependent on the source Effective

10 ANTENNA TYPES AND EMISSIONS HPA, UK

11 THE SUTTON COLDFIELD STUDY E. Dolk et al. Cancer incidence near radio and television transmitters in Great Britain Am J Epidemiol 145:1-9 (1997)

12 THE SYDNEY STUDY We compared cancer incidence and cancer mortality [ ] on the basis that the RFR becomes progressively weaker with the square of the distance from the towers. No account was taken of ground reflections, nor of signal reduction by buildings, vegetation or ground undulations. [ ] Some measurements made by the Commonwealth Department of Communications found actual levels to be five times less than those calculated. B. Hocking et al. Cancer incidente and mortalità and proximity to TV towers MJA 165: (1996)

No account was taken of ground reflections, nor of signal reduction by buildings, vegetation or ground undulations.

13 THE CASE OF THE VATICAN RADIO

14 POWER DENSITY - SAME DISTANCE Sito Distance (km) S (mw/m 2 ) f = 1530 khz S (mw/m 2 ) f = 1611 khz S (mw/m 2 ) f = khz 1 2, n.d. < 1 2 2, n.d. < 1 3 1, n.d. 4 2, < 1 5 2, < 1 6 0, n.d. n.d. 7 1, < 1 < 1 8 1,875 < 1 < ,675 5 n.d. < , n.d. < 1

< 1 2 2,650 283 n.d. < 1 3 1,625 181 107 n.d. 4 2,575 34 4 < 1 5 2,250 100 18 < 1 6 0,850 99 n.

15 POWER DENSITY - SAME DIRECTION Site Distance (km) S (mw/m 2 ) f = 1530 khz 1 2 2,325 2, Theoretical ratio: 2, ,625 2,575 2, Actual ratio: 1,56 6 0, , ,875 < 1 9 2, ,075 17

ratio: 2,66 3 4 5 1,625 2,575 2,250 181 34 100 Actual

16 INDOOR EXPOSURE Attenuation due to the sheilding effect of walls Number of walls Thickness Material

17 OCCUPATIONAL EXPOSURE LEVELS

18 VARIABILITY IN EXPOSURE LEVELS M. Bini et al. Exposure of Workers to Intense RF Electric Fields that Leak from Plastic Sealers. J. Microwave Power 1986

19 THE SIMPLE CASE: MOBILE PHONES Same source Standard use

20 EXPOSURE ESTIMATION The relation between RF absorption and mobile phone use is complicated since it depends on: Phone use Call time, frequency of calls, time since the beginning of use Way in which the phone is held Characteristics of the phone Characteristics of the network Location of absorption in the head

time since the beginning of use Way in which the phone is held

21 THE INTERPHONE STUDY Based on a questionnaire including questions on: Start of use Modality of use over the time Frequency of calls Mean duration of calls Phone models (TACS/NMT, GSM 900, GSM 1800, UMTS)

22 WHAT MAY HAVE AFFECTED SAR? Evolution of phone models Evolution of networks Evolution of fares Evolution of services (SMS vs voice)

23 MODIFICATION OF SAR OVER THE TIME

24 EVALUATION OF SAR DISTRIBUTION IN THE HEAD Numerical modelling route Generic handsets (numerical/physical) Step 2 Step 1 Real handsets (over 400 models) Compliance testing route SAR distributions in realistic head models (derived from MRI) Step 3 SAR distributions in homogeneous head models (compliance phantoms)

25 IDENTIFICATION OF PHONE CLASSES Measurement data from France and Japan on 110 commonly used phones used at different frequencies and with different technologies

26 TYPICAL SAR DISTRIBUTION IN A HOMOGENEOUS HEAD

27 AVAILABLE MEASURED SAR DISTRIBUTIONS 126 phones tested 76 Japanese (800 or 1500 MHz) - TWIN 48 GSM (900 & 1800 MHz) - TWIN & SAM 2 NMT (900 MHz) - SAM Configurations Antenna retracted/extended (where applicable) Cheek/tilt Right/left side of head 1051 distributions in all

28 ELLIPSOIDAL REPRESENTATIONS Ellipse defined to enclose all points with SAR above half of the spatial peak SAR Characterise by 7 variables x,y co-ordinates of peak SAR in plane Area and major axis length of the ellipse Ratio: distance or SAR max from perimeter to major axis length Tilt angle of major ellipse axis Depth of ellipse

29 IDENTIFICATION OF PHONE CLASSES 3Db contours of the ellipses corresponding to the classes defined by frequency bands Analyses of phone type, antenna type, etc Only discriminating factors -tilt/cheek position -frequency band Y X

30 TUMOUR LOCALISATION FROM SCANS Aims: To identify as precisely as possible the location of the origin of the tumour and its contours, To evaluate the RF exposure at that location

31 PHONE OUTPUT POWER Software-modified phones (SMPs) were developed by 4 manufacturers to record the actual emitted power during calls. The use of SMPs allowed to investigate: Effects of adaptive power control (APC) and discontinuous transmission (DTX) on power Relation to call circumstances (indoor/outdoor; statiorary/moving; urban/rural)

32 CALL STATISTICS Location Australia Denmark Finland France Germany Israel Italy Sweden New Zealand UK North 1 UK North 2 No. of users No. of calls Total No. of calls/day 4.2 ( ) 2.5 ( ) 3.8 ( ) 6.7 ( ) 2.6 ( ) 10.9 (0.5 41) 5.4 ( ) 2.3 ( ) 4.5 ( ) 2.5 (0.2 12) 2.8 ( ) Mean call duration (min)

33 OUTPUT POWER DISTRIBUTION Germany 900 MHz Sweden 900 MHz 52 % Occupancy Occupancy 33 % 0 0 Highest Power Level Lowest Highest Power Level Lowest

34 POWER STATISTICS FROM SMPs Location Australia Denmark Finland France Germany Isral Italy New Zealand Sweden UK North 1 UK North 2 Average power at 900 MHz Average power at 1800 MHz % of samples per call made at max power Total % of calls made entirely at max power

35 OVERALL EFFECT OF APC Much less than originally expected Phones spend a lot of the time at full power Only Swedish data follows text books Mean phone powers vary from country to country GSM (92-170) mw GSM (47-88) mw

36 CONSTRUCTION OF THE EXPOSURE GRADIENT S last last last tot l, b, t = X i, l, c * Averageclass( SARt, c, x * Convc ) * Ti * Hi * Yijmup, b, t * P, i, b, t telephone= 1 operator = 1 i = 1 * O i S tot,l,b,t i X i,l,c SAR t,c,x Conv c T i H i Y ijmup,b,t P i,b,t O i total specific energy t a given location (l), for a given band (b) (450, 900, 1500, 1800, 1900 MHz) and a specific technology (t) (GSM, CDMA, etc) month of use of the phone (within a period defined by the operator and the phone), proportion of the SARmax received at that location, for the phone (belonging to class c and operating with technology t in frequency band b) SAR for the phones in the class and technology conversion factor to go from SAR10 g to SAR in the cell with the highest average SAR in Gridmaster in specific class of phones average calltime per month (in minutes) derived from CAPI use of hands-free devices from CAPI effect of output power modifiers rural/urban proportion of traffic in band b and technology t from network operators effect of other modifiers as appropriate (APC, DTX, ) from external data/expert opinion

How To Know If You Are Safe To Use An Antenna (Wired) Or Wireless (Wireless)

How To Know If You Are Safe To Use An Antenna (Wired) Or Wireless (Wireless) 1 2 The range of RF spans 3 KHz (3000 Hz) to 300 GHz (300 million Hz) Frequencies of RF devices range from the low frequency AM broadcasts (80 MHz) to higher frequency mobile phones (1900 MHz) smart meters