Measurements of Radiofrequency Radiation with a Body-Borne Exposimeter in Swedish Schools with Wi-Fi

Our research group published recently a study on radiofrequency (RF) radiation in schools using an exposimeter. RF emissions in the classroom were measured by the teachers in order to approximate the children’s exposure. Teachers in grades 7–12 carried a body-borne exposimeter, EME-Spy 200, in school during 1–4 days of work. Eighteen teachers from seven schools participated. The mean exposure to RF radiation ranged from 1.1 to 66.1 μW/m². The highest mean level, 396.6 μW/m², occurred during 5 min of a lesson when the teacher let the students stream and watch YouTube videos. Maximum peaks went up to 82,857 μW/m² from mobile phone uplink.  The exposure levels varied between the different Wi-Fi systems, and if the students were allowed to use their own smartphones on the school’s Wi-Fi network or if they were connected to GSM/3G/4G base stations outside the school. An access point over the teacher’s head gave higher exposure compared with a school with a wired Internet connection for the teacher in the classroom. All values were far below International Commission on Non-Ionizing Radiation Protection’s reference values, but most mean levels measured were above the precautionary target level of 3–6 μW/m² as proposed by the Bioinitiative Report. The length of time wireless devices are used is an essential determinant in overall exposure. Measures to minimize children’s exposure to RF radiation in school would include preferring wired connections, allowing laptops, tablets and mobile phones only in flight mode and deactivating Wi-Fi access points, when not used for learning purposes.

In Table 10 in the article examples of methods to reduce children’s exposure to RF radiation in schools are given

1. Wired connection to both teachers and students and no wireless networks or devices in school is the optimal choice. If this is not possible:
2. Wired connection to each classroom
a. to the teacher’s laptop,
b. for the students to download large files and videos.
3. To reduce exposure from Wi-Fi networks in school:
a. turn off Wi-Fi access points when not used for learning purposes,
b. position Wi-Fi access points outside of classrooms,
c. use directional Wi-Fi access points, which radiate into the direction of the client’s device.
4. Keep laptops and tablets in flight mode when Internet is not needed for learning purposes.
5. Wired connection to a landline telephone in each classroom could minimize the need for mobile phones for contact.
6. Mobile phones, including smart phones, could be left at home or collected in turned off mode. If allowed, they should be carried only in flight mode during school hours.

 

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High radiofrequency radiation at Stockholm Old Town in Sweden

Exposure to radiofrequency (RF) radiation was classified as a possible human carcinogen, Group 2B, by the International Agency for Research on Cancer at WHO in 2011. Outdoor RF radiation levels were measured during five tours in Stockholm Old Town in April, 2016 using the EME Spy 200 exposimeter with 20 predefined frequencies. The results were based on 10,437 samples in total. The mean level of the total RF radiation was 4,293 μW/m2 (0.4293 μW/cm2). The highest mean levels were obtained for global system for mobile communications (GSM) + universal mobile telecommunications system (UMTS) 900 downlink and long‑term evolution (LTE) 2600 downlink (1,558 and 1,265 μW/m2, respectively). The town squares displayed highest total mean levels, with the example of Järntorget square with 24,277 μW/m2 (min 257, max 173,302 μW/m2). Measurements in the streets surrounding the Royal Castle were lower than the total for the Old Town, with a mean of 756 μW/m2 (min 0.3, max 50,967 μW/m2). The BioInitiative 2012 Report defined the scientific benchmark for possible health risks as 30‑60 μW/m2. Our results of outdoor RF radiation exposure at Stockholm Old Town are significantly above that level. The full report can be found here.

High radiofrequency radiation at the Stockholm Central Station in Sweden

We measured the radiofrequency (RF) radiation at the Stockholm Central Station in Sweden in November 2015. The full study can be read here. The exposimeter EME Spy 200 was used and it covers 20 different RF bands from 88 to 5,850 MHz. In total 1,669 data points were recorded. The median value for total exposure was 921 µW/m² (or 0.092 μW/cm²; 1 μW/m²=0.0001 μW/cm²) with some outliers over 95,544 µW/m² (6 V/m, upper detection limit). The mean total RF radiation level varied between 2,817 to 4,891 µW/m² for each walking round.

Hot spots were identified, for example close to a wall mounted base station yielding over 95,544 µW/m² and thus exceeding the exposimeter’s detection limit, see Figure below. A man is standing with his smartphone just a couple of meters below a base station (see arrow). In that area maximum measured power density in the GSM +UMTS 900 downlink band from the base station was 95,544 µW/m², which is the upper limit of measurement for EME Spy 200.

Almost all of the total measured levels were above the precautionary target level of 3 to 6 µW/m² as proposed by the BioInitiative Working Group in 2012. That target level was one-tenth of the scientific benchmark providing a safety margin either for children, or chronic exposure conditions. Considering the rapid progress of this technology, including 5G that is to be launched in the near future, it is important to monitor current RF radiation exposure in the environment.