Increasing telecommunication networks has resulted in the development of massive towers to support mobile phone antennas. This has been the case in the majority urban and built-up areas where the number of antennas is high. The increasing number of radio broadcasting stations has also contributed to the shift from lower operating frequencies to higher frequencies. Increasing the bandwidth is done to manage increased high traffic in the urban areas. The high frequencies generally require a higher number of towers. As such, the exposure to electromagnetic radiation in v urban cities increases. Mostly, the visual impact of the towers on health risk has been the main focus for the media and the population. There is a need for focus and pay attention to the human exposure to radiation that may come from the radio services.
Approaches that have been adopted in literature for researching human exposure to non-ionizing radiation include laboratory or theoretical work, which accounts for about 15% of the research work. Theoretical work may involve the use of mathematical models while lab work involves testing done on animals. Secondly, another approach is classification based on interviews which account for about 18% of the work that has already been done in researching non-ionizing radiation effects. Under the classification based on interviews, researchers use predefined questions, which may include aspects such as diseases and populations living in the proximity of towers. A third approach that has been used by researchers and accounts for 30% is using surveys. The surveys are based on results of existing studies on non-ionizing radiation exposure to humans. The fourth and most used approach is the measurement campaigns. The measurement campaigns account for 37% of all the research work that has been documented.
The research in this study is located in Natal, Brazil and focuses on non-ionizing radiation measurements on VHF and UHF bands. The measurement of electric field levels is done by determining the exposure rates which are then compared to the human exposure limits. A sample of radio services that operate in the range of these bands is provided in the study.
Methodology
Exposure rate data and information were measured using a Rohde and Schwarz spectrum analyzer that was connected to an isotropic probe. A measurement campaign approach was adopted.
Results
The main criteria followed in analyzing the results involved the computation of the exposure rate (ER) for the various services. The services involved include TV broadcast, radio broadcast, mobile telephony services and WLAN. The TV broadcast services recorded the highest value of the exposure rate even in areas where the mobile telephony towers were higher in number. A major aspect to consider in understanding these results is that most of the measurement points were not aligned with the main lobe of the mobile telephony antennas. As such, a more accurate assessment of the influence of the mobile telephony services can be achieved if the number of measurement points that align with the mobile telephony antennas can be increased.
Alignment needs to be based on the elevation and azimuth position where the higher levels of radiation are expected to be emitted from the mobile telephony antennas. The value of ER obtained for the TV broadcast is well below the limit. The implication from this is that the influence of mobile telephony is minimal, and more focus needs to be placed in the alignment of measuring points with the mobile telephony antennas.
Discussion Question
What is the upper limit for human exposure? If the ER is greater than unity what does it mean and what needs to be done?
