## 4 Discussion
It has been extensive study, and the results are valued well below the limits allowed by ICNIRP. We see that the maximal total field value was measured in a residential environment and was equal to 3.9 V/m (0.0255 W/m\({}^{2}\)) from GSM900 signals, 11 times below the ICNIRP reference levels for electric field strength. [PERSON] [127] also reports that from the last ten years of studies reviewed on RF-EMF exposure in indoor environments, the highest average maximum exposure levels considering all RF-EMF frequency bands were 1.14 V/m (0.0034 W/m\({}^{2}\)) in offices, which are also very far from the maximum permitted values. The contributions of [PERSON] [142] are also very interesting, reporting that the exposure cut-off points for the most exposed groups were lower than 0.5 V/m (663.13 uW/m\({}^{2}\)) in all studies, a value that is much lower than the reference levels established by the ICNIRP. On the other hand, [PERSON] [105], who obtained an overview of the changes in exposure when new technologies were introduced during the period 2013 to 2019, reported that the population exposure is well below the limits established by the ICNIRP and relatively constant over time despite the introduction of new technologies. In this same study, [PERSON] shows a graph with the total values of all frequency bands measured in relation to the limit values for the different measurement points. We could even see that there is a value of 200,000 uW/m\({}^{2}\) in the 800 MHz band in 2017 (Figure 5 of this review) that seems to be high, but it really is not; this value is equivalent to 0.20 W/m. [PERSON] highlights that levels increased in 2017 and then decreased again at the end of the year and beyond 2018 due to reconfigurations at mobile operators and the installation of new base stations. Some UMTS base stations were removed during the same period, and with the implementation of 4G technology, these totals also decreased. In another of the most recent works, [PERSON] [123], who has reviewed 144 investigations, shows that in homes, schools and offices, the average exposure to RF-EMF was between 0.04 and 0.76 V/m (4.24 uW/m\({}^{2}\) and 1532.10 uW/m\({}^{2}\), respectively); and the mean values for outdoor exposure ranged between 0.07 and 1.27 V/m (13.00 uW/m\({}^{2}\) and 4278.25 uW/m\({}^{2}\), respectively), with the downlink signals from mobile phone base stations being the most significant contributors. Finally, the highest levels ranged between 1.97 V/m (0.0103 W/m\({}^{2}\)) measured at public transport stations, with the downlink being the most significant. We also observed that the values are very small compared to the limits established by ICNIRP. The review that precedes the present article is [PERSON] [30], which includesmeasurement studies with volunteers and/or with a trained researcher (touring a specific area, one or several microenvironments, an entire city, walking or in some means of transport), which covers the period from 1 January 1998 to 31 December 2021, in which other important and preceding reviews were also mentioned. In this last review, it is highlighted that after comparing 56 investigations, the minimum value was measured in Egypt with a value of 0.00100 \(\upmu\)W/m\({}^{2}\) (1.00 nW/m\({}^{2}\)) in 2007, and the highest average was measured in Belgium with a value of 285,000 \(\upmu\)W/m\({}^{2}\) (0.285 W/m\({}^{2}\)) in 2019, also very far from the reference limits established by the ICNIRP.