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| ORIGINAL ARTICLE |
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| Year : 2019 | Volume
: 42
| Issue : 3 | Page : 84-89 |
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Radio frequency nonionizing radiation exposure burdens to the population at major market centers in Ibadan metropolis, Nigeria
Nnamdi Norbert Jibiri1, Enokela Pius Onoja1, Idowu Richard Akomolafe2
1 Department of Physics, Radiation and Health Physics Research Laboratory, University of Ibadan, Ibadan, Nigeria
2 Department of Physical and Mathematical Sciences, Faculty of Science, Crown-Hill University, Ilorin, Nigeria
| Date of Submission | 07-Feb-2019 |
| Date of Decision | 18-Mar-2019 |
| Date of Acceptance | 07-Apr-2019 |
| Date of Web Publication | 06-Nov-2019 |
Correspondence Address:
Mr. Idowu Richard Akomolafe
Department of Physical and Mathematical Sciences, Faculty of Science, Crown-Hill University, Ilorin
Nigeria
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/rpe.RPE_4_19
There has been proliferation of mobile phone base station towers in recent years due to an expansion of mobile telephone networks. This has been accompanied by an increase in the community concern about possible radiation exposure due to the radio frequency (RF) radiation emissions from antennae mounted on the base station towers. This work presents RF measurements and information on the levels at selected markets in Ibadan, Nigeria. The highest RF power density of 499.6 μW/m2 obtained at Global System for Mobile Communication (GSM) 1800 band occurred at Apete market. The lowest RF power density of 0.1 μW/m2 was also obtained at Alesinloye for GSM 1800, Dugbe, and Ogunpa for GSM 900; at this point of measurement, the base transceiver station was not in the line of sight. The measured RF levels were compared with the maximum permissible limit for nonoccupational exposure with respect to the Radiocommunications (Electromagnetic Radiation – Human Exposure) Standard 1999 which specifies a maximum nonoccupational exposure limit of 2 W/m2 (equivalent to 200 μW/cm2) at relevant base station frequencies. The results showed that the RF exposure levels were several orders of magnitude below the maximum permissible limits around the environments of the major markets in the city of Ibadan.
Keywords: Base stations, exposure level, Global System for Mobile Communication, Ibadan, nonionizing radiation, radio frequency
How to cite this article:
Jibiri NN, Onoja EP, Akomolafe IR. Radio frequency nonionizing radiation exposure burdens to the population at major market centers in Ibadan metropolis, Nigeria. Radiat Prot Environ 2019;42:84-9 |
How to cite this URL:
Jibiri NN, Onoja EP, Akomolafe IR. Radio frequency nonionizing radiation exposure burdens to the population at major market centers in Ibadan metropolis, Nigeria. Radiat Prot Environ [serial online] 2019 [cited 2019 Nov 13];42:84-9. Available from: http://www.rpe.org.in/text.asp?2019/42/3/84/270446 |
| Introduction | |  |
The Global System for Mobile Communication (GSM) network has evolved from 2G to 4G mobile system. The growth of mobile phone communications during the past 15 years has been tremendous, and this has led to the installation of more base transceiver station (BTS) antennas in Ibadan, Nigeria. There are over 139 million active GSM lines in Nigeria. This huge amount of active lines has attracted more BTS and millions of mobile phone handsets within the country. At present, almost every individual, homes, offices, and institutions make the use of mobile phones and other mobile communication services. According to the Nigerian Communications Commission (NCC), the number of deployed BTS or cell sites, by the four operators (i.e., MTN, Globacom, Airtel, and Etisalat), grew from few in 2001 to about 44,000 in May 2014. As at May 2014, the GSM operators collectively have a subscriber base of approximately 178 million lines, of which 131 million lines were active. This astronomical growth of GSM deployment suggests a proportionate increase in the level of radio frequency (RF) radiation emitted into the country's air space, a trend that deserves regular monitoring through appropriate measurements of the RF power given out by these base stations.[1]
At communication frequency, human body behaves, as a dielectric and the electromagnetic (EM) radiation generated by mobile phone base station is able to penetrate through it. The EM radiation is called the fourth pollution source besides air, water, and noise by the environmentalists. Although exposure from BTS antennas is far less than that from handheld mobile devices, the public appears to be more concerned about the safety of BTS. For this reason, the World Health Organization (WHO) has recommended to undertake research studies on this project. In addition, measurements of EM field (EMF) radiation from base station antennas of the various mobile network operators are compared with the recommended EMF levels by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) and other organizations.
RF radiation covers frequencies (3 KHz–300 GHz) used for communication, radar, and satellites. Over the years, the transmission of radio waves has become an established technology which is taken for granted and which among other things provides for broadcasting to our homes for entertainment, the most development resulting in the domestic satellite dish antenna. The proliferation of cellular antennas and other RF-generating devices has led to concerns about the potential health effects from exposure to RF radiation. The short-term thermal effects of RF radiation on humans are well documented, but less is known about the long-term health effects.
There are different studies that have been carried out in various countries around the world to assess the level of RF radiation exposure to the public. Few of such studies have been carried out in Nigeria[1],[2],[3],[4] and other countries.[5],[6],[7],[8],[9],[10] There are a number of national and international regulatory standards and recommendations dealing with EM exposure in the RF range. These limits are generally very similar and usually based on recommendations from the WHO[11],[12],[13] and the ICNIRP guidelines.[14] These limits are set with a wide margin to protect people from any known negative health effects of both short- and long-term exposures to EMF. Basic restrictions on exposure are provided for both occupational exposure and public exposure. The standard posed by the ICNIRP guidance for public exposure limits is 9.2 W/m2 for GSM 1800 MHz, 4.7 W/m2 for GSM 900 MHz, and 10.2 W/m2 for 2100 MHz. Safety guidelines for exposure of the public to the RF radiation from transmitting antennas are set by different organizations all over the world. The most widely accepted standards are those developed by the Institute of Electrical and Electronics Engineers (IEEE) and the American National Standards Institute (ANSI), the ICNIRP, and the National Council on Radiation Protection and Measurements (NCRP). These standards are expressed in power density in mW/cm2. The 1992 ANSI/IEEE exposure standard for the general public is 1.2 mW/cm2 for antennas operating in the 1800–2000 MHz range. The limit for antennas operating in the 900 MHz range is 0.57 mW/cm2. The ICNIRP standards are slightly lower and the NCRP standards are identical. The NCC adopted the ICNIRP guidelines[15] for limiting the risk of RF exposure to the public in Nigeria. Thus, for GSM 900 transmitting band (935–960 MHz), power density limit is 4.7 W/m2 and for GSM 1800 transmitting band (1800–1880 MHz), it is 9.2 W/m2. The market is the place where a lot of activities take place including buying and selling. It is a place where people meet to transact business outside the usual exchange of money for goods and services. The emergence of the internet and other data networks of electronic-related activities takes place in the market which involves call, browsing, etc. Several research works were done on the environment to determine RF and EMF effects on the people in the city of Ibadan such as[16] but none considered the major market where daily business activities are carried out with attendant business calls and communications. This forms the basis for this research work to investigate the burden of RF on the population at the major markets in Ibadan metropolis. Thus, the study was designed to estimate the RF exposure levels from mobile communication signals at the major markets with a view to determining the power density from GSM, Code-Division Multiple Access (CDMA), 2G (Second Generation), 4G (Fourth Generation) and 3G (2100 MHz band) signals around major markets in the city of Ibadan.
| Materials and Methods | | |
Selection of markets
There are about 1.6 million GSM lines in Ibadan and about 900,000 registered active GSM lines as at 2014, making up 60% of that of the whole of Oyo State, Nigeria. The large market size which the city's population size connotes is one major prospect of its viability, in addition to its accessibility to other areas within and outside the country. Everybody loves shopping, but in Ibadan, the capital of Oyo State Nigeria, the inhabitants take it to another level. Being a very big city, Ibadan is dotted with a number of notable markets which have continued to draw in thousands of buyers daily. The cosmopolitan nature of Ibadan city coupled with its large population has attracted many sellers and buyers. The prices of goods in these markets in Ibadan are considered cheap by many compared to relatively expensive markets in states like Lagos, Nigeria. Ibadan city is gradually growing to become a major economic center in Nigeria. In this work, the following major markets were considered: Agbeni, Bodija, Alesinloye, Ogunpa, Oja-Oba, Gbagi, Oje, Dugbe, Bashorun, and Apete covering the ten local government areas making up Ibadan.
Radio frequency measurement of the markets
A spectrum analyzer SPECTRAN HF 60105 (Aaronia AG) with a calibrated OmniLOG 90,200 antenna with frequency range 50 MHz–3.5 GHz and a global positioning system for geographical coordinate measurement were employed for the measurements. Five measurements were taken at each market place for GSM 900, 1800 MHz frequency, and 3G bands. Spectral measurements were taken for the frequency bands. Frequency was selected on the analyzer as allocated by the NCC. The analyzer was mounted on a tripod stand of height 1.5 m – this is about the height of the trunk of an average human. Measurements were made 1.5 m above ground level at 60-m intervals from the selected locations from each of the five selected locations in each market. The spectrum analyzer was set to maximum hold function, where the peak value of each signal was recorded over each sweep. This was done to estimate the worst-case scenario of exposure at each location. The spectrum analyzer was also set to a frequency sweep range of 925–2491 MHz (covering GSM 900, GSM 1800, and CDMA) frequency bands. Measurements were taken at each point for 6–8 min, and all necessary precautions were taken to reduce systematic errors. GSM 900 and GSM 1800 frequency band signal exposures were mainly focused only in this study because they are the most common type of mobile communication systems in Nigeria and they have the highest numbers of BTSs in most places. CDMA mobile systems are usually associated with low exposure, and they have few BTSs in the country. Power density measurements were taken at these five points in the ten markets. It was observed generally, that the exposure values do not follow any specific trend, but varied from point to point depending on the environmental factors and broadcasting power of the base station antennas near and around the market places. [Table 1] presents the coordinates of the sampling location in each of the markets. | Table 1: The coordinates of the selected markets in Ibadan where measurements were taken
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Radio frequency measurement
The spectrum analyzer measures the received power density S W/m2 according to Equation (1).[2],[3],[4]
Where P is the power received by the OmniLOG antenna in dBm, G is the gain of the antenna in dBi, and λ (m) is the wavelength of the received signal. The RF broadband power density survey meter, TES-90 Electrosmog meter, manufactured by Less EMF, NY, USA, was used to measure power density in W/m2 due to all RF signals in the frequency of 50 MHz to 3.5 GHz. It can also measure the electric field intensity (E) and magnetic intensity (H) along a different axis. As shown in Equation (2), the electric field intensity (E) and magnetic intensity (H) are related to the power density:[15]
S was measured in W/m2. In free space, the ratio of the amplitudes of the electric field strength and magnetic field strength equals 377 Ω which is the characteristic impedance of free space :
In the near field, both electric and magnetic fields must be measured. When RF radiation passes through any biological medium, some of the energy from the radiation field is absorbed by the medium. The dosimetric quantity used to determine the absorbed energy from radiation field is the specific absorption rate (SAR). It is a measure of the time rate of energy absorption per unit mass and is usually expressed in units of watts per kilogram (W/kg). The SAR is expressed as:
In terms of electrical parameters, the SAR can be calculated using:[17],[18],[19]
Where σ = conductivity of material, E = electrical field, and ρ = mass density of the tissue equivalent media.
| Results and Discussion | | |
The radio frequency exposure levels at the markets
The results of measurements of RF power density around the selected markets are presented in [Table 2] for GSM 900, [Table 3] for GSM 1800, and [Table 4] for 3G networks. | Table 2: The range and mean power density for Global System for Mobile Communication 900 MHz band at the market
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 | Table 3: The range and mean power density for broadband measurement for Global System for Mobile Communication 1800 MHz band at the market
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Exposure levels of GSM 900 MHz at the markets
[Table 5] shows the lowest and the highest measurements of the power for GSM 900, GSM 1800, and 3G frequency bands at the selected markets. | Table 5: The lowest and highest measurements power density for Global System for Mobile Communication 900, 1800, and 3G frequency bands at the selected markets
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At Alesinloye market, the highest reading measured was 136.1 μW/m2 and the lowest was 1.5 μW/m2 with the spectrum analyzer set at GSM 900. The geometric mean and geometric standard deviation for broadband meter reading were 542.8 μW/m2 and 1.3 μW/m2, respectively. At Gbagi market, the highest reading measured was 1.2.4 μW/m2 and the minimum was 1.2 μW/m2, whereas the geometric mean and geometric standard deviation for the broadband readings were 407.5 μW/m2 and 2.0 μW/m2, respectively. The geometric mean and geometric standard deviation of power density were also indicated in [Table 2] for GSM 900 band.
At Oja-Oba market, the highest reading measured was 489.3 μW/m2 and the minimum was 1.4 μW/m2 with the spectrum analyzer set at GSM 1800; the geometric mean and geometric standard deviation for broadband meter reading were 528.9 μW/m2 and 1.3 μW/m2, respectively. Furthermore, at Agbeni market, the highest reading measured was 11.3 μW/m2 and the minimum was 0.6 μW/m2 for GSM 1800 spectrum analyzer, and the geometric mean and geometric standard deviation for broadband meter reading were 567.4 μW/m2 and 1.3 μW/m2, respectively. [Table 3] shows the geometric mean and geometric standard deviation of power density readings taken for GSM 1800 band.
At Bodija market, the highest reading measured was 42.4 μW/m2 and the minimum was 17.6 μW/m2 with the spectrum analyzer set at 3G band network; the geometric mean and geometric standard deviation for broadband meter reading were 443.9 μW/m2 and 2.0 μW/m2, respectively. Furthermore, at Dugbe market, the highest reading measured was 106.2 μW/m2 and the minimum was 1.1 μW/m2, the geometric mean and geometric standard deviation for broadband meter reading were 636.1 μW/m2 and 1.2 μW/m2, respectively. [Table 4] shows the range and the mean of power density readings taken for 3G band. Although this increase might be influenced by other RF emission gadgets such as radio transmitters and TV antennas, the variation in power densities in the markets is due to distance from the base stations; at Apete and Oja-Oba markets, the measurements were taken at a closer distance from the tower. However, measured power density received depends on the power of the transmitter at the mast. At some places within the markets, you could see two towers from two BTSs. The power density at a particular point on the ground will be the sum of the power densities from the two antennas. Power density decreases as the distance increases and as you get closer to the antenna.
The highest power density measured in the GSM 900 band was at Bashorun (432.1 μW/m2) and the lowest reading measured was at Ogunpa (0.1 μW/m2). The highest geometric mean of the power density for GSM 900 was 65.2 μW/m2 measured at Apete market and the lowest was 2.8 μW/m2 at Ogunpa market, as shown in [Table 2].
Exposure levels of GSM 1800 at the markets
The highest power density measured in the GSM 1800 band was at Apete market (499.5 μW/m2), the measurement was taken close to the BTS, and the lower power density was mostly measured with BTS in the line of sight. The lowest reading was measured at Agbeni and Ogunpa markets (0.6 μW/m2). The highest geometric mean power density for GSM 1800 was 17.3 μW/m2 measured at Bodija market and the lowest mean exposure was 1.9 μW/m2 at Alesinloye market, as shown in [Table 3].
Exposure levels of 3G network at the markets
The highest power density measured in the 3G band was at Alesinloye (198.4 μW/m2) and the lowest reading measured was at Agbeni (1.2 μW/m2). The highest geometric mean of power density for 3G network was 51.9 μW/m2 measured at Alesinloye market and the lowest geometric mean was 3.9 μW/m2 at Gbagi market shown in [Table 4].
Comparison of result with set limits
The results presented in [Table 2], [Table 3], [Table 4] are quite low compared with the ICNIRP reference standard of 4.5 μW/m2 for GSM and 3G ranges of frequencies as presented in [Table 6].[20] The presented study, therefore, indicates that the exposure scenario in the markets studied can be considered to be within a safe limit. However, telecommunication networks are dynamic systems which develop and grow daily; efforts should, therefore, be made to control and regulate indiscriminate siting of masts to ensure unnecessary exposure of the public. The highest measurement at Apete in [Table 5] is still low when compared with standard limit for safety [Table 6]. The plot power density against selected markets is given in [Figure 1]. This is to show the graphical distribution of the power density. | Table 6: The International Commission on Non-Ionizing Radiation Protection safety limits for public exposure
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 | Figure 1: A plot of average power density (μW/m2) against the selected markets
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This study was conducted to evaluate the RF radiation levels due to mobile phone base stations in selected markets located in Ibadan, Nigeria. Practical measurements in terms of power density were undertaken in five random locations within the market to determine exposure levels. This was done to evaluate the levels of exposure burden they pose to the population at the market. For each of these markets, the measurements were taken without considering any particular distance from the BTS covering the market area. This work presents field measurement data of the RF radiation from GSM base stations in selected markets in Ibadan, Nigeria. The power densities of GSM base stations in the selected markets under consideration were evaluated. The highest value of 499.6 μW/m2 was recorded at Apete market for 1800 band, followed by 489.3 μW/m2 at Oja-Oba market. These values were quite low compared to international standard limits in line with those adopted by the ICNIRP which is 9.1 μW/m2 for the public and 22.5 μW/m2 for those professionals involved in telecommunication industry. It could, therefore, be concluded that RF radiation from these BTSs poses no significant health risk to the population at the market centers in Ibadan city. However, when considering the implications of these results, it is important to note that the sampling locations were randomly selected and that the values were assumed to be influenced by some known and unknown factors such as EM radiation from FM and TV antennas and satellite.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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[Figure 1]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]
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