# Radio Frequency Electromagnetic Fields Exposure Assessment in Indoor Environments: A Review
## 3 Results
### Educational Buildings
#### Exposure in Public and Private Transportation  
A high number of studies focused on the assessment of the RF-EMF exposure on transportation could be found in literature, due to the peculiar conditions of being densely populated environments where wireless connection quality could be not stable in time. In a study by [PERSON] et al. [PERSON] et al. (2018) the RF-EMF exposure was quantified using portable devices with a high sampling rate in different public transport vehicles, in Switzerland, Ethiopia, Nepal, South Africa, Australia and the United States of America. The measurements were taken for about 30 min with a sampling rate equal to 4-5 s, depending on the instrument. Across various modes of public transport, the authors found that total exposure, arising from uplink and downlink transmission, broadcasting and WiFi, ranged between 0.37 V/m (1.32% of the lowest ICNIRP reference level for the considered frequency band) in bus in Switzerland and 0.86 V/m (3% of the lowest ICNIRP reference level for the considered frequency band) in auto rickshaw in Nepal. Considering separately the different contribution to the exposure, the authors found that uplink transmission was the most relevant exposure source in trains, with the highest values in Switzerland (with a maximum value of 0.47 V/m, 1.24% of the ICNIRP reference level, in Zurich), while, for the other types of vehicles the most relevant source of exposure was found to be the downlink one, with values ranging from 0.28 V/m (0.74% of the ICNIRP reference level) on the bus in Switzerland to 0.85 V/m (2.25% of the ICNIRP reference level) on the auto rickshaw in Nepal. Relevant differences were observed between the uplink exposure across public transportation in Switzerland and Nepal probably because Switzerland is technologically more advanced than Nepal where fewer people traveling on public transportation use smartphones. In a similar study by [PERSON] et al. [PERSON] et al. (2018), the authors investigated the repeatability and representativeness of personal RF-EMF exposure measurements, across different micro-environments, including different public transport vehicles. The authors observed large variations in RF-EMF exposure depending on the type of transportation that is used, with the lowest total levels of exposure in cars (E\({}_{\text{rms}}\) equal to 0.18 V/m, equal to 0.64% of the lowest ICNIRP reference level for the considered frequency band) when not using any RF-EMF emitting devices, and the highest total exposure in tram and trains (E\({}_{\text{rms}}\) equal to 0.38 V/m and 0.23 V/m, respectively, equal to 1.36% and 0.82% of the lowest ICNIRP reference level for the considered frequency band). A study by [PERSON] et al. [PERSON] et al. (2018) investigated the levels of RF-EMF exposure inside the metro infrastructure in Warsaw by frequency-selective exposimeters. Results showed that most of the exposure was due to mobile phones base transceiver stations and handsets used by the passengers (GSM 900 and UMTS 2100) and to local wireless Internet access (WiFi 2G). The highest values were observed for GSM900, with median and 75 th percentile values of the E-field equal to 0.22 V/m and 0.37 V/m for the downlink (equal to about 0.5% and 0.9% of the ICNIRP reference level) and to 0.28 V/m and 0.47 V/m for uplink of the handsets (equal to about 0.7% and 1.1% of the ICNIRP reference level). Broadband measurements, including the dominant signal emitted by staff radiophones (151 MHz), showed that the level of this exposure of engine-drivers does not exceed 2.5 V/m. Two recent studies [PERSON] et al. (2018); [PERSON] et al. (2018) assessed the impact on the passengers' exposure of the deployment of a miniature small cell or a femtocell in a train car in order to improve the coverage and the capacity of a mobile network service on the train.