# Radio Frequency Electromagnetic Fields Exposure Assessment in Indoor Environments: A Review
## 3 Results
### Educational Buildings
#### Exposure in Public and Private Transportation
Three sources of RF-EMF were considered: (1) the subject's mobile phone (a near-field source); (2) the base station to which the mobile phone was connected (a far-field source), and in case of the small-cell scenario; (3) the macrocell as well, as it is still present and radiating. The highest exposure values in terms of median Specific Absorption Rate (SAR) equal to 61 \(\upmu\)W/kg were found for the GSM 900 technology, without the presence of small cell/femtocell on the train. In both studies the authors found that by connecting to a small cell of to a femtocell, the exposure of the user could realistically be reduced. In another study by the same authors [PERSON] et al. (2018) the contribution of RF-EMF originating from other people's devices to total own whole-body absorption in a train environment has been assessed in a simulation study. Absorption in a train environment due to base station's downlink is compared with absorption due to uplink of the user's own mobiledevice and absorption due to the uplink of 0, 1, 5, or 15 other nearby active users. Results showed that the contribution of other in-train users is not negligible: 15 other users connected to a GSM900 macro cell base station can induce absorption rates up to 14.3 \(\upmu\)W/kg, i.e., 24% of the absorption rate induced by a user's own device, equal to 60.6 \(\upmu\)W/kg. This corresponds for the considered scenario to a contribution of 19% to the total absorption rate (equal to 74.9 \(\upmu\)W/kg) when calling yourself and a contribution of 100% when not calling yourself. A UMTS femtocell deployment in this environment drastically reduces total absorption and makes the other users' contributions to total absorption negligible. Some studies focused on the assessment of the RF-EMF exposure inside road vehicles by using computational methods [66; 67; 68]. In the study by [PERSON] and colleagues [66] numerical dosimetry for adult and children models exposed to several wireless communication systems (UMTS, WiMax, and Bluetooth) localized in different positions within a partly shielded environment represented by a realistic car model, considering different exposure scenarios. Results showed that for a single operating device, the maximum whole body SAR for adults and for children exposure is 1.39 and 1.58 mW/kg, respectively. For two simultaneously emitting sources, these values increase to 2.04 and 2.13 mW/kg. For all considered exposure scenarios, the whole-body average SAR is more than 40 times lower than the ICNIRP general public exposure limit [43]. The maximum 10 g-averaged localized SAR was found in the head, trunk, and limbs, with maximum SAR values in the limbs, at least 10 times lower than ICNIRP limits [43]. for both adult and children models. The whole-body average SAR values for children are found to be typically 1.1-1.3 times higher than those of adults. Under several exposure scenarios, the local SAR in the limbs of children models is 2-3 times higher than corresponding values in adult models. Analyzing the power density distributions within the car for one, two, and three simultaneously emitting devices, the authors found that the homogeneity of the power density distribution increases with increasing number of simultaneously operating transmitters, thus suggesting that the use of several wireless communication devices within a car leads to exposure levels that are several orders of magnitude below the ICNIRP general public exposure limit [43]. In the paper by [PERSON] et al. [67] the specific absorption rate (SAR) induced in mobile phone users inside a vehicle was evaluated by finite-difference time-domain method in different scenarios, including handedness, passenger counts, and seating locations. The authors simulated the situation in which only one of the passengers is talking on a mobile phone (i.e., the user) at a fixed location for all the studied cases, while the rest of the passengers were without any wireless communication device.