György Thuróczy National Research Institute for Radiobiology and Radiohygiene

1. PUBLIC EXPOSURE TO RF FROM INSTALLED SOURCES: SITE MEASUREMENTS AND PERSONAL EXPOSIMETRY György Thuróczy National Research Institute for Radiobiology and Radiohygiene Dept. of Non-Ionizing Radiation Address: 1221 Budapest, Anna u 5. Hungary Tel: +36 1 482 2019 fax: +36 1 482 2020 thuroczy@hp.osski.hu, www.osski.hu

3. Outline • Characteristics of EMF environment • Sources • Exposure levels • Exposure variations • RF measurements • in-situ survey around mobile base stations • Survey in underground (metro) stations by broadband measurements • personal RF exposimetry

4. Characteristics of EMF environment and human exposure • Main features of RF exposure: • wide range of exposure levels (environmental vs. occupational) • Spatial variations in space • Inhomogeneous and partial body exposure • Variations of exposure level in time • Rapid development of new technologies with appearing new frequencies and signals • Rapid changes of exposure situations

5. Characterization of human exposure to RF

6. (Valberg et al, 2007)

7. GSM 900 GSM 1800 Changing the environmental exposure to RF • Environmental RF exposure always changes in time: • rapid proliferation of RF sources (i.e. base station, BS) • raise of ambient RF radiation:1980 (Tell, USA): ~ 50 W/m2 1999 (Hamnerius, Sweden): ~ 500 W/m2 • Increasing contributions of GSM sources in the RF range (up to 39-61 %) • Increasing the indoor exposure due to the new wireless devices Mean contributions from different RF sources in Sweden(mean percent part of the total ratio from RF environment given in percent, 30 MHz-2100 MHz), Hamnerius 1999

8. Occupational Public Human exposure in the environment and workplaces: wide range of level Mantiply, 1997 Medium frequency range: 0.3-3 MHz

9. Occupational Public Human RF exposure in the environment and workplaces: wide range of level Mantiply, 1997 Very High Frequency range: 30-300 MHz

10. Occupational Public Human RF exposure in the environment and workplaces: wide range of level Mantiply, 1997 Ultra High Frequency range: 0.3-3GHz

11. RF exposure levels - outdoor (Valberg et al, 2007)

12. RF exposure levels - indoor (Valberg et al, 2007)

13. Exposure and sources compared to EU Recommendation of public exposure limits For example: 100%= 100 T@50 Hz ; 4,5 W/m2@900 MHz

14. Exposure and home sources compared to base stationsin percent of the EU Recommendation for public limit For example: 100%= 100 T@50 Hz ; 4,5 W/m2@900 MHz

15. Measurements – Why? Typical cases when RF exposure prediction or measurement are required: • Compliance testing of human exposure (workers, general public) according to compliance levels of ICNIRP or EU reference levels (typically required by public, local authority) • Source characterisation(typically required by operators) • Pre-installation measurement (requested typically by local governments) • New antenna installation(in case of many existing antennas) • Compliance testing of electromagnetic compatibility(EMC) • Scientific request for epidemiological study (i.e. to define cohorts within the population)

16. Aims and corresponding methods:Environmental RF exposure

17. In situ (on-site) EMF measurement • Measured value: field strength and variations • advantages: • We have a long term experiences of the methods • Well developed measurement devices are available • Provide a relevant characterisation of the real exposure of the given site • Possibility to validate by numerical methods • Disadvantage and limitations: • Large time requested (i.e. spatial mapping, monitoring, frequency selective measurement) • Expert’s work is needed (expensive) • May have large variations in field strength • May not relevant to the real individuals’ exposure

18. from J.Wiart from J.Wiart Site measurements of RF exposure:variations and uncertainties • The exposure of population show a very large variation. Basically there are four different sources of such variationsand uncertainties: • large scale variation because of variations of exposure between different places and between different times at a given location (influenced by how the measurement sites were selected, may extend to few orders of magnitude). • signal variations induced by propagation path and technology • temporal variations in traffic density at a given location(2-3 fold) • uncertainty in measurements due to the measurements techniques(up to 30 %)

19. Measurements • Survey on mobile base stations by frequency selective measurements • Survey in underground (metro) stations by broadband measurements • Personal RF exposimetry by frequency selective exposimeter

20. Survey on mobile base stations by frequency selective measurements Issues and questions: • What levels of exposure to radiofrequency fields are in the environment to the vicinity of base stations? • How does the increased deployment of antennas relate to exposure levels? • Do these exposures to electromagnetic fields from base station antenna comply with standards and regulations? • Is any relation between the public exposure and the distance from the antenna?

21. Methods/1 • According to the COST-STM frequency selective measurements were performed. • The selected frequencies effectively covered the frequencies used for GSM 900 and GSM 1800 down-links. • The assumption was made that far field conditions applied. Therefore the measured electric fields could be converted to power densities. • Measurements were performed using wide band antennas connected to a spectrum analyser. • The antenna was always mounted on a tripod at slightly varied heights around 1.5 m.

22. General outline of frequency specific measurements, comprising an antenna, a spectrum analyser and data storage facilities.

23. Methods/2Spectral measurements • Antenna and spectrumanalyzer • PBA 10200 (ARCS) 80 MHz-2200 MHz • Advantest U4941 • Measurements • Sweep: 40 MHz, (925-965 MHz) • RBW: 100 kHz, VBW: 100 kHz • x ,y, z orthogonal, max-hold • data storage (700 points) • distance measurements with laser beam • Evaluation • From SRAM to Excel spreadsheet • dbV/m, V/m, mW/m2 • According to COST STM

24. Methods/2 • The effective power density was obtained by the vectorial summation of the orthogonal electric field (V/m) components. Using the formulae P = E2/377, the result is expressed as the effective power density in mW/m2. • All data were obtained from spot measurements (N=292), and in most cases no information concerning the variations of the field strengths versus time was available. • During the sample (scanning) time, the maximum field strength in each direction could be obtained by using the “peak hold” function of the analyser. • The data analysis was generally performed off-line. The measured exposures were expressed in mW/m2. The data were expressed as: • Ssum (mW/m²): The sum of all power densities in the respective GSM down-link band • Si (mW/m²):The highest power density measured at a single frequency in the respective GSM down-link band

25. Frequency spectrum of GSM 900 MHz base station: down-link

26. Power densityspectrum of GSM base station: down-link

27. Ssum Median: 0,156 mW/m2(CI 95%: 0,0209 - 4,922, N = 292) Ssum (mW/m²): The sum of all power densities in the respective GSM band

28. Distribution histogram of measured power density in different ranges of all measurement sites Ssum (mW/m²): The sum of all power densities in the respective GSM band

29. Power density in different Type of environment of all measurements (mW/m2) Ssum (mW/m²): The sum of all power densities in the respective GSM band Si (mW/m²):The highest power density measured at a single frequency in the respective GSM band

30. Power density in different type of environment Ssum (mW/m²): The sum of all power densities in the respective GSM band ICNIRP/EU limit on 900 MHz @ 4500 mW/m2 on 1800 MHz @ 9000 mW/m2

31. Ssum (mW/m²): The sum of all power densities in the respective GSM band EU limit at 900 MHz @ 4500 mW/m2 at 1800 MHz @ 9000 mW/m2

32. Base station survey:Results and Discussion • According to the results of present spectral measurements at more than 290 sites, the exposure levels from the base stations were many times below the ICNIRP/EU limits (4500 - 9000 mW/m2) respectively. • The exposure did not exceed the tens of mW/m2 (a few microwatt/cm2) at locations accessible to public. • Within 300 m of the base station no clear expression could be found between the exposure levels and distances similarly to other studies.

33. Measurement #2 • Survey on mobile base stations by frequency selective measurements • Survey in underground (metro) stations by broadband measurements • Personal RF exposimetry by frequency selective exposimeter

34. GSM Base station in METRO station (n=83) GSM panel antenna toward peron Radiated cables Peron B x Metro tunel x Peron A 1-8,1 V/m x GSM panel antenna toward the tunel 0,3-0,4 V/m 2-14,6 V/m

35. GSM Base station in METRO station: broadband measurements (N=83) Average: 3,3 V/m, SD: 2,07 V/m; Median: 2,9 V/m (CI 95%: 1,4-7,19)

36. GSM Base station in METRO station: broadband measurements

37. Measurement #3 • Survey on mobile base stations by frequency selective measurements • Survey in underground (metro) stations by broadband measurements • Personal RF exposimetry by frequency selective exposimeter

38. Personal RF exposimetry • According to our previous site measurements: • The main RF field variations comes from the location therefore • Assess the personal exposure = assess the exposure where the person is sleeping, working, walking….

39. Personal RF exposimetry: aims • Record the RF exposure coming from main wireless systems and broadcast. • Avoid interference with the person’s activity • Long term frequency selective recording of human exposure to RF

40. Personal RF exposimetryEvaluation of RF general population exposure • Dosimetric problems: • Difficulties in retrospective exposure assessment for epi studies • Exposure misclassification due to different RF sources • Long term exposure variations in time, exposure variation in space • Objectives • Characterise RF exposure levels of individuals • Evaluate the importance of different exposure sources in the general and personal environment • Identify, if possible, the main factors which may predict exposure levels • Further Aim • support for any future epidemiological study

41. Personal RF exposimetry: the device • Personal exposure meter (PEM): • Antennessa DSP090(France) • Frequency bands recording selectively: • FM (88 to 108 MHz) • TV (174 to 223 MHz) & (470 to 830 MHz) • GSM 900 Tx(mobile phone: 875 to 915 MHz) & Rx (base station: 935 to 960 MHz) • GSM1800 Tx(1710 to 1795 MHz) & Rx(1805 to1880 MHz) • UMTS Tx (1920 to 1980 MHz) & Rx (2110 to 2170 MHz). • dynamic range 40 dB within the E-field range: • from 0.05 V/m to 5 V/m at each band

42. • Isotropy (free space): 2 dB at 95% confidence (1 dB at 66%) • Vertical dosimeter Personal RF exposimetry:sources of variations and uncertainties • Spatial variations in signal strengths induced by various propagation path and technology (few orders), • Isotropy (i.e. close to the body) • Frequency selectivity (co-channel error) • sensitivity and accuracy • Personal variation due to position (proximity) to the human body

43. dosimeter Personal RF exposimetry:sources of uncertainties: influences of the body • The body has an influencebut in each frequency band ofinterest the total exposureis the sum of differentsources and reflectionstherefore the exposure isoften coming fromeverywhere. • The mean values as obtained with the PEMs tend to underestimate the free field measurements (64% - 72%). • Taking into account this underestimation of the free field conditions, the simple free space model might be a valid approximation for the real exposure. Measurement in the SwissCom laboratory, Lehmann et al, 2007

44. Personal RF exposimetryPersonal frequency selective exposimeter for RF range Antennessa DSP 090

45. Measurements with personal exposimeter in Budapest (Hungary) • The purpose of the current study was to evaluate the usefulness of an RF personal exposimeter (dosimeter) for assessing individual radiofrequency (RF) exposure in an urban environment. • Measurements taken by RF personal dosimeter (PEM) were also compared to preliminary site measurements taken around mobile base stations.

46. Measurements with personal exposimeter in Budapest (Hungary) • Subjects • n=21 participants(plus 4 pilot study, 2 eliminated by technical reasons) • Residency in Budapest (capital, 2,5 million inhabitants) • Most of them were our colleagues from the institute or their relatives • Protocol • time-activity diary by the subjects following the form designed for the study (we used similarly forms for 50 Hz personal exposimetry) • Time of the survey: 24 h data recording • Device, recording and location • personal exposure meter (PEM): Antennessa DSP090 • Recording: sample rate 15 sec, ~1440 minutes (24 h) • Location: mounted on the body and /or in a carry bag. Fix location near the bed at night and close to subject indoors (i.e. on the desk, table etc.)

47. Methods: exposure metrics and analysis • Selected exposure metrics: • Duration of (exposure, activity)time (min) • Field intensity (V/m): max., arithmetic mean, S.D. • Time Weighted Average (TWA) TWA: Average field intensity x duration of time (Vm-1 x min) • Exposure metrics analyzed according to: • Frequency bands (channels) • Different time periods (activity) • Mainly theGSM(rx)/DCS(rx)/TV4&5 were analysed so far (fixed installed sources: base stations, broadcasts antennas).

48. Exposure metrics and analysis: time periods • Total measuring time (1440 min – 24 h) • Periods according to activity types: • (1)home (2)bed (3)travel (4)work (5)other/else • Periods when the measured field exceeded the detection threshold of the meter:(>0,05 V/m) • Periods when the measured data fall into different bins according to field level ranges: • (a-low) 0,05-0,1 V/m (b-medium) 0,1-1,0 V/m (c-high) 1,0-5,0 V/m • Periods when the measured field was equal to the detectionlimit (=0,05 V/m, or may below)

49. Exposure time above 0,05 V/m Mean percent of total time (24h), when subjects were surely exposed above 0,05 V/m by channels and activity types

50. (900 MHz) (1800 MHz) Averages of periods (minutes) within 24 h (~1440 min)when the data of measured field fall into different bins of exposure ranges according to selected channels (base stations and TV4&5) by different activity types.