Mapping of radio frequency electromagnetic field exposure ... - Nature

Journal of Exposure Science and Environmental Epidemiology (2016) 00, 1–5 © 2016 Nature America, Inc., part of Springer Nature. All rights reserved 1559-0631/16

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ORIGINAL ARTICLE

Mapping of radio frequency electromagnetic field exposure levels in outdoor environment and comparing with reference levels for general public health Mustafa Cansiz1, Teymuraz Abbasov2, M. Bahattin Kurt1 and A. Recai Celik1 In this study, radio frequency electromagnetic field exposure levels were measured on the main streets in the city center of Diyarbakır, Turkey. Measured electric field levels were plotted on satellite imagery of Diyarbakır and were compared with exposure guidelines published by the International Commission on Non-Ionizing Radiation Protection (ICNIRP). Exposure measurements were performed in dense urban, urban and suburban areas each day for 7 consecutive days. The measurement system consisted of high precision and portable spectrum analyzer, three-axis electric field antenna, connection cable and a laptop which was used to record the measurement samples as a data logger. The highest exposure levels were detected for two places, which are called Diclekent and Batıkent. It was observed that the highest instantaneous electric field strength value for Batıkent was 7.18 V/m and for Diclekent was 5.81 V/m. It was statistically determined that the main contributor band to the total exposure levels was Universal Mobile Telecommunications System band. Finally, it was concluded that all measured exposure levels were lower than the reference levels recommended by ICNIRP for general public health. Journal of Exposure Science and Environmental Epidemiology advance online publication, 2 November 2016; doi:10.1038/jes.2016.64 Keywords: electromagnetic field; exposure level; ICNIRP; mapping; measurement; public health; radio frequency

INTRODUCTION People are increasingly exposed to radio frequency (RF) electromagnetic field (EMF) with rapid development of technologies such as broadcasting and mobile communication systems. In society, there is a growing concern about RF EMF exposure. Assessment and visualization of exposure levels in the environment are very important for epidemiological researches.1–6 There are many studies that discuss the effects of RF EMFs on living organisms in literature. Related with usage of wireless phone, RF EMFs were classified by International Agency for Research on Cancer7 as possibly carcinogenic to humans (Group 2B) based on an increased risk for glioma, which is a malignant type of brain cancer. RF EMF affects not only human health but also ecological life of animals and plants. In some scientific studies, it was detected that EMF might cause decline in the sparrow population8 and in productivity in white storks.9 In addition, it was observed that EMF may influence duckweed growth10 and reduce the radial growth of pine trees.11 Unlike the studies mentioned above, with cell phone usage of more than 10 years, the international pooled analysis of data obtained from 13 countries did not find increased risk of glioma or meningioma.12 When considering all of these, measurements and evaluations of RF EMF exposure levels are crucial for these researches. There are various spatial and temporal measurement technics in the literature. Personal exposure measurement13–16 is one of the newest measurement technics. Besides, it is necessary and very

useful for epidemiological researches to monitor the individual exposure level of participants during their daily activities. Thus, it enables experts to investigate the exposure according to different frequency bands, signal levels and other signal properties. Spot measurement17–20 is one of the static measurement technics to observe the RF EMF exposure level of location of interest. It allows to observe variation of the exposure level over time. Another measurement technic is mobile measurement technic21 that measurement device is mounted on the top of vehicle. In this way, many measurement samples are taken in a short time in a vast area. All of these measurement technics enable us to analyze the RF EMF exposure in detail. Displaying the measurement result on a map has many benefits. The RF EMF exposure levels can be investigated visually on the satellite map street by street. By means of this method, the exposure levels around the sensitive places such as school, kindergarten and hospital can be detected. Then, if it is necessary, the exposure level can be improved below the official limit. Some international organizations, such as International Commission on Non-Ionizing Radiation Protection,22 Institute of Electrical and Electronics Engineers23 and Federal Communications Commission,24 have developed guidelines to protect humans against the adverse health effects of non-ionizing EMFs. For this purpose, exposure limits or reference levels have been recommended by them. Electric field strength (E), magnetic field strength (H) and power density (S) are some electrical quantities used for reference levels. Many developed countries, including Turkey, have adopted ICNIRP guidelines.

1 Department of Electrical and Electronics Engineering, Dicle University, Diyarbakır, Turkey and 2Department of Electrical and Electronics Engineering, İnönü University, Malatya, Turkey. Correspondence: Dr Mustafa Cansiz, Department of Electrical and Electronics Engineering, Dicle University, Diyarbakır 21280, Turkey. Tel.: +90 412 248 8401. Fax: +90 412 248 8218. E-mail: [email protected] Received 7 May 2016; accepted 4 October 2016

Mapping of RF EMF levels in outdoor environment Cansiz et al

2 The aim of this study was to show the RF EMF exposure levels on the satellite map and then determine the highest exposure levels in the city center of Diyarbakır in Turkey during a week on the measurement route. It was detected that whether there were the sensitive places around the highest RF EMF exposure levels. Measurements of six different RF EMF bands were performed on the main streets during a week on the same route as mobile. Total exposure levels of six different RF EMF bands were calculated and analyzed. The main contributor band to the total exposure was detected statistically. Finally, all measurement results were compared with the reference levels of ICNIRP for general public health.

Producing Thematic Map The number of measurement samples was 472 samples/day to compare mobile measurements with each other equally. The file containing the maximum instantaneous E values, date, time, latitude and longitude was imported to MapInfo.29 The maximum instantaneous ETotal values (resultant RF EMF exposure levels) were classified into five groups. 0 (V/m) ≤ ETotal o1 (V/m) values were represented in white color and the smallest values were in this group, 1 (V/m) ≤ ETotal o2 (V/m) values were represented in green color, 2 (V/m) ≤ ETotal o 3 (V/m) values were represented in blue color, 3 (V/m) ≤ ETotal o4 (V/m) values were represented in yellow color and finally, 4 (V/m) ≤ ETotal o 8 (V/m) values were represented in red color and the highest values were in this group. All the maximum instantaneous ETotal values were depicted as colored points on the satellite map. Thereby, a thematic map was produced for Wednesday.

MATERIALS AND METHODS Measurement studies were conducted on the main streets as mobile in the dense urban, urban and suburban areas between 10 November 2014 and 16 November 2014 in the city center of Diyarbakır, which is one of the most populated cities in Turkey. Six different RF EMF bands: FM (87.5–108 MHz), TV3 (174–230 MHz), TV4-5 (470–862 MHz), GSM900 (935–960 MHz downlink frequency), GSM1,800 (1,805–1,880 MHz downlink frequency) and Universal Mobile Telecommunications System (UMTS) (2,110–2,170 MHz downlink frequency) were measured every day of the week between 17:00 and 18:20 h. According to the information obtained from the local operators, the busy hour of mobile network operators was 17:00 local time and the busy hour of mobile network operators may vary seasonally. Then, measurement results were displayed on the satellite map as colored points.

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RESULTS AND DISCUSSION There are many FM and terrestrial TV broadcast transmitters in Diyarbakır. FM broadcast operates at very high frequency band and the terrestrial TV broadcast operates at very high frequency band and ultra-high frequency band. In Turkey, there are three mobile network operators. All mobile network operators in the city center of Diyarbakır provide Global System for Mobile Communications (GSM) and UMTS services. GSM and UMTS frequency bands of two mobile network operators are 900 and 2,100 MHz but the GSM and UMTS frequency bands of the other operator are 1,800 and 2,100 MHz, respectively. The measurements were taken from Monday to Sunday. The highest electric field strength was measured on Wednesday. The highest mean electric field strength was calculated on Wednesday. Because of these reasons, Wednesday was shown as a separate map figure in this study. Thematic map of RF EMF exposure levels on Wednesday was shown in Figure 1. As seen in Figure 1, large variations in the RF EMF exposure levels were observed but two places which are called Diclekent and Batıkent as shown in Figure 2 were measured as the highest RF EMF exposure levels during 7-day measurements. Diclekent was depicted 6 days in red point and 1 day in yellow point. Batıkent was depicted 3 days in red point and 4 days in yellow point. As shown in Table 1, the highest ETotal value for Batıkent is 7.18 V/m and for Diclekent is 5.81 V/m. All measurement samples were analyzed statistically and then it was found that UMTS band was the main contributor to the total exposure levels. The maximum instantaneous E values of sub-bands in Table 1 also confirm it statistically. The total calculated exposure as a percentage of the ICNIRP general public reference level for each row in the Table 1 were calculated according to the Eq. (2). There are several reasons for why these two places have the highest exposure levels. Each place has a base station for mobile phone and these two base stations have common features. They have both GSM and UMTS antennas, which were installed on the first floor level. Moreover, these base stations are very close to the main streets. As seen in Figure 2, one base station is 115 m far away from Batıkent point and the other one is 165 m far away from Diclekent point. Therefore, exposure levels around these places were measured high. On the contrary, FM and terrestrial TV transmitters were far away from the streets where mobile measurements were taken.

ETotal represents the maximum instantaneous total exposure level and the others represent the maximum instantaneous E values for each band. Channel bandwidth for FM broadcast,27 GSM90026 and GSM180026 is 200 kHz, for UMTS28 5 MHz and for TV3 and TV4-5 broadcasts27 7 MHz. Resolution bandwidth is recommended as at least a quarter of channel bandwidth.25 Resolution bandwidth for FM broadcast, GSM900 and GSM1800 was set to 50 kHz and for TV3, TV4-5 and UMTS was set to 1,000 kHz for more accurate measurement.

Comparing with Reference Levels of ICNIRP Table 2 shows the reference levels for general public exposure of whole body to time-varying E values. Measurements at 1.70 m height above ground are representative of whole-body exposure. In this study, minimum measurement frequency was 87.5 MHz (FM Band) and maximum measurement frequency was 2,170 MHz (UMTS band). As seen in Table 2, the electric field reference level

Measurement System All measurement samples were taken in the far field region. In the far field region, E values can be converted into H or S values. In this study, E value was measured as RF EMF exposure level. The measurement system consisted of selective radiation meter SRM-3006 (Narda Safety Test Solutions, USA),25 E-field 3501/03 25 isotropic probe, RF cable and a laptop. SRM-3006 is a high precision spectrum analyzer measuring the RF EMF exposure levels in the frequency range from 9 kHz to 6 GHz. E-field 3501/03 isotropic probe is the three-axis electric field antenna frequency range from 27 MHz to 3 GHz, maximum extended measurement uncertainty +2.6/ − 3.8 dB for 85–2,200 MHz and its dynamic range 0.2 mV/m–200 V/m. RF cable connects the SRM-3006 to the three-axis electric field antenna and reduces the external field effects for better measurement. A laptop was used to record the measurement samples as a data logger. SRM-3006 connected to the three-axis electric field antenna was mounted on the top of the vehicle. The three-axis electric field antenna was placed at 1.70 m height above ground. In order to not cause traffic jam, the average speed of the vehicle on the route was about 40 km/ h. if the average speed of the vehicle exceeds this speed, it would cause a decrease in the number of measurement samples. The total length of the measurement route is 35 km and some boulevard and street names on the route are Silvan Boulevard, Elazığ Street, Tekel Street, Şanlıurfa Boulevard, Hatboyu Street, Ekinciler Street, Kışla Street, Gazi Street, Fiskaya Street and Dicle University Campus. The worst case was taken into account during the mobile measurements. Therefore, the program written by us obtained the maximum instantaneous E values for each band, date, time, latitude and longitude at an interval of 10 s from the SRM-3006 and recorded them. Then, total exposure levels (ETotal) were calculated by summing root mean square (rms) values of six RF EMF bands by using the relation:26 E Total ¼

qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi E 2FM þ E 2TV3 þ E 2TV4 - 5 þ E 2G900 þ E 2G1800 þ E 2UMTS

Journal of Exposure Science and Environmental Epidemiology (2016), 1 – 5

© 2016 Nature America, Inc., part of Springer Nature.


3

Figure 1. center.

Thematic map of RF EMF exposure levels on Wednesday. Bold values indicate the two highest RF EMF exposure levels in the city

Figure 2.

The highest RF EMF exposure levels in the city center of Diyarbakır.




4 Table 1.

The highest ETotal exposure levels and other sub-bands during a week.

Location point

Measurement date

ETotal (V/m)

ICNIRP (%)

EFM (V/m)

ETV3 (V/m)

ETV4-5 (V/m)

EGSM900 (V/m)

EGSM1800 (V/m)

EUMTS (V/m)

10.11.2014 10.11.2014 11.11.2014 11.11.2014 12.11.2014 12.11.2014 13.11.2014 13.11.2014 14.11.2014 14.11.2014 15.11.2014 15.11.2014 16.11.2014 16.11.2014

3.64 4.48 5.81 4.07 5.65 7.18 4.51 3.92 4.82 3.87 5.42 3.53 4.78 3.98

0.50 0.82 1.23 0.57 1.24 1.63 0.65 0.55 0.75 0.55 0.91 0.40 0.67 0.75

0.11 0.08 0.13 0.08 0.11 0.08 0.13 0.08 0.10 0.08 0.12 0.09 0.11 0.09

0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08

0.13 0.12 0.17 0.12 0.23 0.12 0.17 0.11 0.14 0.12 0.17 0.13 0.14 0.12

1.98 2.89 3.12 1.79 3.40 2.63 1.70 1.84 1.91 2.08 1.82 1.43 1.27 3.17

1.75 1.32 1.18 2.79 0.46 2.74 1.16 2.94 1.83 1.06 2.07 0.21 1.24 0.14

2.50 3.16 4.75 2.36 4.48 6.09 4.01 1.82 4.02 3.08 4.66 3.22 4.43 2.39

Diclekent Batıkent Diclekent Batıkent Diclekent Batıkent Diclekent Batıkent Diclekent Batıkent Diclekent Batıkent Diclekent Batıkent

All electric field strength values are rms. Bold values indicate the two highest RF EMF exposure levels in the city center.

Table 2.

Reference levels of ICNIRP for general public exposure to time-varying electric fields. Electric field strength (V/m)

Frequency range 10–400 MHz 400–2,000 MHz 2–300 GHz

28 1.375f 61

1/2

f is the frequency in MHz and all electric field strength values are rms.

for FM band and terrestrial TV3 broadcast band is 28 V/m, for terrestrial TV4-5 broadcast band is ~ 39 V/m. Similarly, the electric field reference level for GSM900 is ~ 41 V/m, for GSM1800 is ~ 58 V/m and for UMTS band is 61 V/m. The highest ETotal values in the city center of Diyarbakır were 7.18 V/m for Batıkent and 5.81 V/m for Diclekent. There is a school where it is about 125 m away from Batıkent. Furthermore, the maximum instantaneous E values of sub-bands were listed in Table 1. To check that whether the total exposure level exceeds the safe exposure level, the following Eq. (2) should be applied to E values for thermal considerations. X300 GHz i41 mHz

Ei E L;i

2 1

CONCLUSIONS The RF EMF exposure levels on the main streets in the city center of Diyarbakır were shown on the satellite map and then two highest RF EMF exposure levels were detected. By means of this method, considering these thematic maps for public health, RF planning engineers who work for mobile network operators may avoid the installation of new base stations in locations where existing RF exposure levels are already very high. It was statistically determined that the main contributor band to the total exposure levels was UMTS band. Three mobile network operators also provide the UMTS service in Turkey at 2,100 MHz frequency band. It was concluded that all measured RF EMF exposure levels even two highest exposure levels in the city center of Diyarbakır were lower than the reference levels recommended by ICNIRP for general public health. CONFLICT OF INTEREST The authors declare no conflict of interest.

ACKNOWLEDGEMENTS This work was supported by Dicle University Scientific Research Projects (Project Number: 13-MF-25)

ð2Þ

Where Ei denotes the electric field strength at frequency i, EL,i denotes the electric field reference level from Table 2 for general public exposure. When Eq. (2) (87.5 MHz ≤ frequency ≤ 2170 MHz) was taken into account, it was detected that all measured exposure levels even the highest exposure levels did not exceed the reference levels of ICNIRP for general public health. During a week on the measurement route, the highest exposure levels for FM, TV3, TV4-5, GSM900, GSM1800 and UMTS bands are 0.34, 0.10, 0.61, 3.86, 2.94 and 6.09 V/m, respectively. Besides, reference level for FM and TV3 bands is 28 V/m and for TV4-5 band is ~ 39 V/m and for GSM900 is ~ 41 V/m and for GSM1800 is ~ 58 V/m and for UMTS band is 61 V/m. The highest exposure levels of the six bands are lower than their reference levels. Thereby, it was found that the total exposure level was below the safe exposure level. In many studies30,31 as well as our study, it was determined that the measurement results were lower than the reference levels recommended by ICNIRP. Journal of Exposure Science and Environmental Epidemiology (2016), 1 – 5

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