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Human Exposure to Non-Ionizing Radiation from Indoor Distributed Antenna System: Shopping Mall Measurement Analysis
Júlia da L. A. Silva, Vicente A. de Sousa,, Marcio E. C. Rodrigues, Fred Sizenando Rossiter Pinheiro, Gutembergue Soares da Silva, Halysson B. Mendonça, Ricardo Q. de F. H. Silva, João V. L. da Silva, Fernanda E. S. Galdino, Vitor F. C. de Carvalho, Lucas I. C. Medeiros
TL;DR
The paper examines how much NIR exposure people may encounter in shopping malls as communication infrastructure expands. It measures electric fields at mall locations selected by crowd flow and nearby DAS or WiFi antennas, under near/far distance and low/high crowd conditions. The highest average and peak fields were 1.96 and 3.26 V/m, respectively, remaining below 8% of ICNIRP and ANATEL limits.
Problem
The study addresses the need to monitor public NIR exposure and compare measurements with current regulatory limits, particularly in crowded locations with indoor antennas.
Method
Researchers measured electric fields at six shopping-mall points selected for high pedestrian flow and nearby DAS or WiFi antennas, comparing near/far distances and low/high crowd scenarios.
Results
1.96 and 3.26 V/m were the highest average and peak electric fields, respectively, both below 8% of the ICNIRP and ANATEL limits.
Takeaways & Limitations
Exposure stayed below ICNIRP and ANATEL limits, while antenna distance and nearby antenna concentration influenced measured electric-field levels.
Takeaways & Limitations
The high-crowd scenario could not ensure worst-case exposure because the sources' maximum transmission powers could not be guaranteed.
Abstract
from arXiv · showhide
It is crucial to monitor the levels of Non-Ionizing Radiation (NIR) to which the general population may be exposed and compare them to the limits defined in the current standards, in view of the rapid rise of communication services and the prospects of a connected society. A high number of people visits shopping malls and since these locations usually have several indoor antennas close to the public, it is therefore a kind of place that must be evaluated. Thus, this work presents measurements of the electric field in a shopping mall located in Natal, Brazil. We proposed a set of six measurement points, following two criteria: places with great the flow of people and the presence of one or more Distributed Antenna System (DAS), co-sited or not with WiFi access points. Results are presented and discussed in terms of the distance to DAS (conditions: near and far) and flow density of people in the mall (scenarios: low and high number of people). The highest peaks of electric field measured were 1.96 and 3.26 V/m, respectively corresponding to 5% and 8% of the limits defined by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) and the Brazilian National Telecommunication Agency (ANATEL).
1. Introduction
The paper motivates monitoring public exposure to NIR as communication services expand, focusing on shopping malls because people gather near indoor antennas. It introduces measurements in a mall with DAS infrastructure and compares exposure against national and international limits.
- NIR exposure monitoring remains important because communication sources are increasing and existing evidence about health effects is largely inconclusive.
- Measurement locations followed recommendations emphasizing maximum-radiation directions and areas with high pedestrian flow.
- DAS provides indoor cellular voice and data coverage, often alongside WiFi access points and signals from multiple operators.
- Shopping malls are relevant measurement settings because they combine high people density, numerous indoor antennas, and antennas located near users.
- The study presents NIR measurements from a shopping mall and discusses them relative to ANATEL and ICNIRP exposure recommendations.
2. Related Works
The related-work analysis combines database-based quantitative mapping with qualitative review of NIR exposure studies, emphasizing indoor measurements and the relatively limited evidence from shopping malls. It also motivates the paper’s mall measurements through attention to standards, people density, indoor antennas, and WiFi coexistence.
- 2.1. Quantitative Analysis: The survey searched Scopus and Web of Science from 2002 to 2022 using keyword groups targeting general NIR research and indoor or outdoor exposure measurements.Group-specific searches used titles, abstracts, and keywords, with title-only searching for Group #0.
- 2.1. Quantitative Analysis: Most reviewed publications used laboratory experiments or measurements, while the majority adopted a neutral conclusion about possible NIR health effects.The classification covered approaches including experiments, measurements, reviews, surveys, and legislation, and conclusions categorized as pessimistic, neutral, or optimistic.
- 2.1. Quantitative Analysis: Publications on general-population NIR measurements increased over time in both groups, but Group #3 showed more persistent scientific interest than Group #2.Group #2 began appearing in 2006, whereas Group #3 appeared earlier in the databases.
- 2.1. Quantitative Analysis: Belgium had the most publications in both groups, while Greece was the only country with a significant difference between Groups #2 and #3.The authors caution that many countries’ field measurements are reported by authorities as technical reports rather than database-indexed scientific papers.
- 2.2. Qualitative Analysis: Few studies measured NIR exposure in shopping malls, and the paper addresses this gap through mall measurements involving indoor cellular DAS, nearby WiFi, standards compliance, and visitor-density effects.The measurement protocol followed a 6-minute duration and sought unperturbed values by isolating equipment from nearby people and reflective materials.
3. Methodology
The study measured broadband electric fields in a Natal shopping mall using ANATEL and ICNIRP guidance, comparing near and far antenna distances under low- and high-flow conditions.
- 3.1. Measurement Procedure: Measurements followed ANATEL and ICNIRP procedures, including 6-minute averaging, unperturbed-value conditions, maximum-radiation and high-people-flow locations.The setup used isolation from nearby people and a wooden tripod to reduce field perturbation and reflection.
- 3.1. Measurement Procedure: The broadband analysis covered 100 kHz–6 GHz and used 40.79 V/m as the most severe exposure limit for the mall’s target services.The limit was based on the 880 MHz mobile-network frequency and also accounted for WiFi bands at 2.4 and 5 GHz.
- 3.2. Measurement Setup: The measurement setup used a Narda broadband field meter, a 100 kHz–6 GHz E-field probe, a wooden tripod, and a 2 m isolation radius.Figure 5 represented the isolation area and near/far distance conditions around a central ceiling-mounted DAS antenna.
- 3.3. Measurement Places: Six locations were selected across two floors based on DAS presence, possible WiFi co-siting, and high pedestrian flow, with four measurement points assigned to each location.The locations covered food-court, commercial, and restaurant-adjacent areas.
- 3.4. Measurement Schedule: Low- and high-flow scenarios were measured at the same points during Tuesday mornings and Friday afternoons, respectively, across two weeks.Google Popular Times information identified 10 a.m. as low flow and 4 p.m., especially Friday, as high flow.
- 3.5. Assumptions and Limitations: The analysis could not guarantee maximum radiation points or a worst-case high-flow exposure because antenna deployment details and maximum source transmission powers were unavailable.All points were treated as lying within the broad maximum-radiation region, while high and low pedestrian flow served as realistic system-load scenarios.
4. Results and Discussions
Measurements showed that exposure generally increased near DAS antennas and with higher crowd density, while remaining well below applicable limits. The highest average and peak fields were 1.96 and 3.26 V/m, respectively, with distance and antenna concentration shaping local variation.
- Limit comparison: Using the stricter FM-band limit increased the exposure ratio, but the measured values remained far below the exposure limit.The analysis considered both the campaign frequency range and a conservative range including FM broadcast frequencies.
- Distance condition: Near-DAS measurements generally showed higher average and peak electric fields than far-DAS measurements.The authors attribute lower far-distance levels to antenna elevation patterns, path loss, and propagation conditions.
- Antenna concentration: Places with multiple nearby DAS or WiFi antennas showed the highest overall exposure and the largest changes between near and far conditions.P2L1, P1L2, and P3L2 were especially affected by nearby antenna concentration.
- People-flow scenario: Higher crowd density generally increased average NIR exposure, although peak values showed no strong relation with the number of people.The authors associate higher averages with increased mobile-network use and possible activation of additional transmitters under higher traffic demand.
- Measurement variability: Corridor locations sometimes reversed the expected crowd-density pattern between measurement rounds, likely reflecting changing propagation and phone use along the corridor.P3L2 and P2L2 displayed opposite behavior across rounds, with one round having higher levels under low crowd density.
5. Conclusions
The study evaluated NIR exposure in a busy shopping mall containing many antennas near users. Across the measured conditions, fields remained below ICNIRP and ANATEL limits, while antenna concentration and crowding influenced exposure levels.
- Main conclusion: The highest average and peak fields were 1.96 and 3.26 V/m, respectively, both below 8% of the ICNIRP and ANATEL limits.Both values occurred at P3L2, which had the largest number of DAS antennas together.
- Antenna placement: Nearby antenna concentration strongly influenced exposure, with P2L1, P1L2, and P3L2 showing significant near-versus-far changes and the highest overall levels.These locations had at least two DAS antennas and/or a nearby WiFi antenna.
- Crowd concentration: The highest electric-field values occurred when the mall was most crowded, indicating an influence of people concentration on exposure levels.This pattern was observed after grouping measurements by the same antenna-distance condition.
- Implications: The study concludes that antenna distance and crowd concentration affect electric fields, but none of the tested situations exceeded ICNIRP or ANATEL limits.The authors emphasize prevention and adequate antenna distribution, especially where people remain for long periods, because health effects remain unresolved.