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Measurement and Mapping of Wi-Fi Radiation Level at Students Hostel in Universiti Sains Malaysia Health Campus
1Abu AmAt, N. H., 2*moHd tAib, N. H., 1SupArdi, N. F. & 1YuSoFF, m. N. S.
ABSTRACT
The increasing use of wireless communication devices, particularly Wi-Fi has raised public concerns on the exposure to electromagnetic field (EMF) and its possible effect on human health. As the exposure level of the EMF radiation varies between different locations, measurement of the EMF strength at various locations is vital. In this study, we aimed to measure the EMF exposure which is described by four specific parameters, specifically 1) the frequency of the wave, 2) the electric field strength E, 3) the magnetic field strength H, and 4) the power density S. This study was performed at the second floor in Nurani hostel block in Desasiswa Murni Nurani, Universiti Sains Malaysia Health Campus. Mapping of Wi-Fi signal and measurement of Wi-Fi radiation level was performed at four specific locations, that are in a student room, television room, prayer room, and ironing room. The average radiation level was compared with the standard limit set by International Commission on Non-Ionizing Radiation Protection (ICNIRP). It was observed that the strength of Wi-Fi signal was highest in students’ room followed by television room. Both of these rooms exhibited high signal strength. While moderate but lower signal level was observed in prayer room followed by ironing room. The electromagnetic field and power density were found highest in students’ room, followed by television room, prayer room, and ironing room. Comparison with standard ICNIRP limit showed that the radiation level is still far below the acceptable limit, which is only 2% of the exposure level. To conclude, students’ room exhibited the strongest Wi-Fi signal and the highest radiation level. However, the radiation level especially power density is still far below the ICNIRP limit.
Keywords: Wi-Fi; radiofrequency; microwave; electromagnetic field (EMF); non-ionizing radiation
1Medical Radiation Program, School of Health Sciences, Universiti Sains Malaysia, 16150 Kubang Kerian, Kelantan, Malaysia
2Department of Radiology, School of Medical Sciences, Universiti Sains Malaysia, 16150 Kubang Kerian, Kelantan, Malaysia
*Corresponding author: N. H. Mohd Taib Email: [email protected]
Tel: +6097676748 Fax: +6097673468 Received: 29 April 2020
Accepted for publication: 25 June 2020
Publisher: Malaysian Association of Medical Physics (MAMP) http://mamp.org.my
https://www.facebook.com/MedicalPhysicsMalaysia
INTRODUCTION
The increasing use of wireless communication devices, particularly Wi-Fi has raised public concerns on the exposure to electromagnetic field (EMF) and its possible effect on human health.
Wi-Fi is a wireless communication technology developed for wireless local area network (WLAN) devices that uses specific electromagnetic (EM) frequencies, specifically in the range of radiofrequency (RF) and microwave. The IEEE 802.11 standards was developed for functioning in 2.4 GHz and 5.0 GHz frequency bands, which are available worldwide (Bellalta et. al. 2016). However, Wi-Fi bands available in Malaysia are all operating at frequency of 2.4 GHz (MCMC 2018).
The increasing use of Wi-Fi has raised public concerns about the impact of electromagnetic radiation on the environment and human health. Though the RF and microwave are non-ionizing radiation, however, there are studies that demonstrated the adverse health effects of Wi-Fi radiation, particularly on cells, fertility, brain, and behaviour (Wilke 2018). Moreover, Pall (2018) highlighted that repeated studies show that Wi- Fi causes oxidative stress, sperm/testicular damage, neuropsychiatric effects including EEG changes, apoptosis, cellular DNA damage, endocrine changes, and calcium overload. It was also stressed further that the biological effects brought by the EMF wave are mainly in the form of non-thermal effects (Pall 2018).
Phys. Technol. Med.
As the exposure level of Wi-Fi radiation varies in different locations, measuring the strength of the EMF wave is important. The objective of the study is to document the specific Wi-Fi exposure level indoor which is described by four parameters, specifically 1) the frequency of the wave, 2) the electric field strength E, 3) the magnetic field strength H, and 4) the power density S.
The exposure level obtained in this study was compared with the standard limit for EMF exposure for public set by International Commission on Non-Ionizing Radiation Protection (ICNIRP) (ICNIRP 1998).
EXPERIMENTAL METHODS
PLACE OF INTEREST
This study was carried out at the second-floor area of Nurani hostel block, Desasiswa Murni Nurani, Universiti Sains Malaysia Health Campus. The hostel was selected as study area as it is one of the main facilities in the campus that is occupied by students. Moreover, the second-floor area was specifically chosen as there are many amenities provided there such as television room, prayer room, ironing room, study room and many others.
MAPPING OF WI-FI SIGNAL
A free software tool namely Ekahau HeatMapper (Ekahau Inc. Virginia, USA) was utilized for mapping of Wi-Fi signal. The software was downloaded from https://
wifi.ekahau.com/heatmapper website and installed in an ASUS X435M series laptop running on Windows 10 Home edition.
Ekahau HeatMapper is able to detect Wi-Fi coverage at the monitored locations. It is also able to locate all the audible access points (APs) and show their configurations and signal strength in the form of heatmap. This software detects 802.11n as well as 802.11a/b/g Wi-Fi signal.
The mapping procedures consisted of four steps.
Firstly, the hostel floor plan was uploaded into the software (Fig. 1). Next, the observer walked slowly together with the laptop around the monitored location.
As the observer walked slowly together with the laptop, the monitored location was marked on the map by left- clicking the laptop touchpad. The software automatically tracks the observer location during the survey and locates all nearby APs. The signal from all APs are presented in the form of heatmaps. Then, the mapping procedures was ended after all areas have been mapped in which Wi-Fi coverage from all APs was displayed on the map.
Finally, the map image was saved in the laptop.
FIGURE 1 The floor plan of the second-floor area of Nurani hostel block
MEASUREMENT OF WI-FI RADIATION LEVEL Measurement of the strength of the EMF in radiofrequency and microwave range was performed using an EMF meter (Tenmars, TM-195). The EMF meter is a tri-axial probe with three channel measurement sensor that allows isotropic measurement over the frequency range of 50 MHz to 3.5 GHz. The size of the EMF meter is 195 (L) 56 (W) 38 (H) mm and it uses 9V battery for power supply. The EMF meter was calibrated first before it is used.
The Wi-Fi radiation level was measured in terms of specific parameters that are the electric field strength, computed magnetic field strength, and computed power density. It is worth mentioning that the EMF meter detects the electrical component (measured in mV/m or V/m) of the EMF. The meter then converts the measurement values to the corresponding magnetic field strength units (μA/m or mA/m) and power density units (μW/m2, mW/m2 or μW/cm2) using the standard far-field formula for electromagnetic radiation (Kimura 2017). The Wi-Fi radiation level was measured by positioning the EMF meter at four selected locations which are at the students’ room, television room, prayer room, and ironing room. The measurement was performed by setting up the EMF meter on a tripod stand (Fig. 2).
The measurement was recorded for six minutes, which is the minimum measurement period recommended by ICNIRP (ICNIRP, 1998). The measurement process was repeated three times and the average value for each parameter was calculated.
COMPARISON WITH ICNIRP LIMIT
The average radiation level was compared with the ICNIRP standard limit for public user. The comparison was made in terms of percentage from the standard limit.
The calculation of percentage was based on Eqn. (1).
(1)
where, Xm is the measured value and Xl is the standard limit.
FIGURE 2 The experimental setup at each monitored location Students' room
Prayer room
Television room
Ironing room
RESULTS
MAPPING OF WI-FI SIGNAL
The Wi-Fi signal detected are summarized in Table 1 and the map obtained is displayed in Fig. 3. It is also noted in the map that the movement of the observer from one location to another was tracked and shown in the map.
It can also be seen in Fig. 3 that the map is displayed in the form of colour-coded map which range from blue to red. Blue and green shows region of high signal level, yellow and orange shows region of medium signal level while red or no colour shows region of weak signal level.
Percentage Xm Xl 100
Phys. Technol. Med.
In this study, it was observed that the student room showed the highest signal strength (-48.0 to -40.0 dBm) followed by television room (-56.0 to -48.0 dBm).
Both locations appeared green in the map. Whereas the prayer room and ironing room displayed moderate signal strength (-72.0 to -64.0 dBm and -88.0 to -80.0 dBm, respectively) and exhibited as yellow region in the map.
TABLE 1 Signal detected from each AP installed at the monitored locations Locations APs
detected Channel SSIDa Security MACb address Max rate/
Mbps Signal
strength/ dBm Students’
room Cisco
802.11g 11 USMWireless Open 44:ad:d9:25:64:a1
54
-48.0 to -40.0 eduroam WPA2 44:ad:d9:25:64:a2
Cisco
802.11n 11 USMSecure WPA2 44:ad:d9:25:64:a0
eduroam WPA2 48:ee:0c:cd:1e:45 144 Cisco
802.11n 1 USMWireless Open B0:e1:7e:00:04:c8
eduroam WPA2 44:ad:d9:25:66:80 144 Television
room Cisco
802.11g 11 USMSecure WPA2 cc:46:d6:89:93:d2
54 -56.0 to -48.0 eduroam WPA2 cc:46:d6:89:93:d0
Cisco
802.11g 6 USMSecure WPA2 9c:1c:12:0f:d1:80
eduroam WPA2 74:a8:a0:2f:d9:6d 54 Prayer room Cisco
802.11g 1 USMSecure WPA2 74:a8:a0:2f:d9:60
54 -72.0 to -64.0 eduroam WPA2 44:ad:d9:25:64:a2
Ironing
room None None None None None None -88.0 to
-80.0
aSSID: service set identifier bMAC: media access control
MEASUREMENT OF WI-FI RADIATION LEVEL Fig. 4 demonstrates the electric field strength, computed magnetic field strength, and computed power density values measured for the three readings. While Table 2 displays the average value for the three measurements of each parameter. It was noted that all of the parameters were highest in students’ room. Next were in television room, prayer room, and ironing room.
FIGURE 3 The Wi-Fi signal shown in the form of colour-coded map
COMPARISON WITH ICNIRP LIMIT
The percentage of the measured value from the standard ICNIRP limit of EMF radiation in range of 2.4 GHz are presented in Table 3. The average values measured for all parameters were found very low compared to the standard limit. Results measured from this study range from as low as 0.0001 % to as high as 0.574 % of the standard exposure limits.
Locations Electric field strength/
mVm-1
Computed magnetic field strength/µAm-1
Computed power density/µWm-² Students’
room 350.37 793.80 161.38
Television
room 172.63 422.37 57.78
Prayer
room 122.43 330.40 30.72
Ironing
room 41.93 94.20 3.04
TABLE 2 The average value of all of the parameters obtained from the three measurements
TABLE 3 The percentage of the measured value from the standard ICNIRP limit of EMF radiation for electric field, computed magnetic field, and computed power density
Locations
Electric field strength
(V/m) Computed magnetic field
strength (A/m) Computed power density (W/m2)
Ma SLb % M SL % M SL %
Students’ room 0.35037 61
0.574 0.000794
0.16
0.496 0.000161 10
0.002
Television room 0.17263 0.283 0.000422 0.264 0.000058 0.001
Prayer room 0.12243 0.201 0.000330 0.206 0.000031 0.000
Ironing room 0.04193 0.068 0.000094 0.059 0.000003 0.000
aMeasured value bStandard limit
FIGURE 4 The parametric values measured at all of the observed locations
Phys. Technol. Med.
DISCUSSION
In this study, mapping of Wi-Fi signal and measurement of EMF radiation level was performed at four specific locations in the hostel block. The measured values were also compared with the standard exposure limit recommended by ICNIRP.
MAPPING OF WI-FI SIGNAL AND MEASUREMENT OF WI-FI RADIATION LEVEL It was observed that the strength of Wi-Fi signal corresponds with Wi-Fi radiation level in which both aspects were noticed highest in students’ room followed by television room, prayer room and ironing room (Figs. 3 and 4). This is thought to be due to two factors, specifically the distance of the observed locations from Wi-Fi router and whether there are barriers between the locations and the router.
The distance of the students’ room and the Wi-Fi router is 1 m. While the television and prayer rooms are located 5 m from the nearest Wi-Fi router there. Whereas the ironing room is located 8 m from the nearest Wi-Fi router. The decreasing of Wi-Fi signal and radiation level is anticipated based on the Inverse Square Law in which radiation emitted from a point source is not linear but constantly spreading out or diverging. The intensity of radiation is inversely related to the square of the distance from the source.
Though the distance of the television and prayer rooms from the router are similar, however lower signal strength and radiation level was noticed in the prayer room as compared to the television room. The wall barrier exist between the router and the prayer room is expected to contribute to such result, as described by previous study (Harwood 2009).
According to Harwood (2009), wireless local area network (WLAN) communications which are based on RF signals require a clear and unobstructed transmission pathway. Among the most common sources of interference are walls constructed from bricks, stones or concrete. The number of walls that an RF signal can pass through while still maintaining sufficient coverage depends on the density of the materials used in a building construction. An example of materials that may cause difficulty for a signal to pass through are concrete and steel walls, particularly causing slow or intermittent connection problems (Harwood 2009).
COMPARISON WITH ICNIRP LIMIT
Though students’ room demonstrates the highest EM field strength and power density (Table 2), however they are still far below the ICNIRP limit, specifically not more than 0.6% of the exposure limit. Whereas exposure level in the other areas was found below 0.3%.
These results agree with another study that was performed at four indoor sites in a library area in which the highest power density documented was 1.25 mW/
m2, which is equivalent to 1.0% of the ICNIRP exposure limit (Supardi et al. 2019).
Our findings are also in agreement with other previous studies on indoor characterization of Wi-Fi radiation level (Jurčević & Malarić 2016; Alkoot 2014).
Jurčević & Malarić (2016) performed the measurement of Wi-Fi radiation level at four indoor sites in a faculty area where the highest power density recorded there was 0.0014 mW/cm2, which is equivalent to 1.4% of the ICNIRP exposure limit. While Alkoot (2014) performed their study at several apartment residences and landed house in which the highest level recorded was 29.8 mW/cm2, which is equivalent to 0.024% of the ICNIRP exposure limit.
CONCLUSION
It is concluded that students’ room exhibited the highest Wi-Fi signal and radiation level. However, the radiation level is still far below the ICNIRP exposure limit.
ACKNOWLEDGEMENT
The authors would like to thank all staff of Desasiswa Murni Nurani, Universiti Sains Malaysia Health Campus for the help and cooperation given throughout the study.
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