I dati vanno letti , secondo me, nel seguente modo:
in poco più di un anno a Basilea l'elettrosmog all'aperto è aumentato del 57%, a Bruxelles del 38% e a Ghent del 20% .
In poco più di un anno !!!
Temporal trends of radio-frequency electromagnetic field (RF-EMF) exposure in everyday environments across European cities
Urbinello D, Joseph W, Verloock L, Martens L, Röösli M. Temporal trends of radio-frequency electromagnetic field (RF-EMF) exposure in everyday environments across European cities. Environ Res. 2014 Aug 12;134C:134-142. doi: 10.1016/j.envres.2014.07.003. [Epub ahead of print].
BACKGROUND: The rapid development and increased use of wireless telecommunication technologies led to a substantial change of radio-frequency electromagnetic field (RF-EMF) exposure in the general population but little is known about temporal trends of RF-EMF in our everyday environment.
OBJECTIVES: The objective of our study is to evaluate temporal trends of RF-EMF exposure levels in different microenvironments of three European cities using a common measurement protocol.
METHODS: We performed measurements in the cities of Basel (Switzerland), Ghent and Brussels (Belgium) during one year, between April 2011 and March 2012. RF-EMF exposure in 11 different frequency bands ranging from FM (Frequency Modulation, 88MHz) to WLAN (Wireless Local Area Network, 2.5GHz) was quantified with portable measurement devices (exposimeters) in various microenvironments: outdoor areas (residential areas, downtown and suburb), public transports (train, bus and tram or metro rides) and indoor places (airport, railway station and shopping centers). Measurements were collected every 4s during 10-50min per environment and measurement day. Linear temporal trends were analyzed by mixed linear regression models.
RESULTS: Highest total RF-EMF exposure levels occurred in public transports (all public transports combined) with arithmetic mean values of 0.84V/m in Brussels, 0.72V/m in Ghent, and 0.59V/m in Basel. In all outdoor areas combined, mean exposure levels were 0.41V/m in Brussels, 0.31V/m in Ghent and 0.26V/m in Basel. Within one year, total RF-EMF exposure levels in all outdoor areas in combination increased by 57.1% (p<0.001) in Basel by 20.1% in Ghent (p=0.053) and by 38.2% (p=0.012) in Brussels. Exposure increase was most consistently observed in outdoor areas due to emissions from mobile phone base stations. In public transports RF-EMF levels tended also to increase but mostly without statistical significance.
DISCUSSION: An increase of RF-EMF exposure levels has been observed between April 2011 and March 2012 in various microenvironments of three European cities. Nevertheless, exposure levels were still far below regulatory limits of each country. A continuous monitoring is needed to identify high exposure areas and to anticipate critical development of RF-EMF exposure at public places.
- • Temporal trends of RF-EMF exposure in various outdoor and indoor microenvironments were investigated over one year.
- • Within one year mobile phone base station exposure levels increased in several Swiss and Belgian microenvironments.
- • In contrast to our hypothesis, mobile phone handset exposure did not increase in public transports.
- • RF-EMF exposure levels still remained substantially below the ICNIRP guidelines.
Overall, our study gives strong indications that, especially mobile phone base station exposure at outdoor areas increased over the study period between April 2011 and March 2012. At outdoor areas temporal increase was higher in Basel׳s area compared to that in Belgium. This may be due to the difference in increased coverage and capacity demands. A further explanation might be that the introduction of precautionary limits in Belgium, which came in effect in 2009 in Brussels (Ordinance of the Brussels Capital Region of 14 March 2007) and in 2011 in Ghent (Ordinance of the Flemish Region of Nov. 2010) and thus was still in the adaption process during the measurement period, could have slowed down the exposure increase, whereas precautionary limits in Switzerland were established since 2001 (ONIR, 1999).
Interestingly, highest exposure levels occurred consistently in trains across all cities with distinct contribution from mobile phone handsets. This has several reasons: the inner space of a train can be considered as a Faraday cage, reflecting emitted radiation by mobile phones. In addition, the density of people using their mobile phones is usually higher in trains than in other environments. Nowadays, mobile phones are not only used for messaging and calls anymore but rather also for using a large variety of web-based applications (apps), such as news alerts, e-mails, mobile television and many other apps, increasing the use of mobile phone handsets during train rides resulting in higher uplink exposure levels. Moreover, location updates or handovers are executed when moving around in order to maintain constant connectivity to the mobile phone base station of the respective area when the device is in stand-by mode or during a call, respectively (Urbinello and Röösli, 2013). These aspects are also relevant for the exposure situation in buses, trams and metros but in these environments we have mainly measured outside the commuting rush hours (Table 1) with a lower passenger density compared to trains.
The impact of the communication infrastructure on the exposure situation can be exemplarily highlighted by comparing measurements in trams and metros. Total mobile phone handset exposure was considerably higher in metros vs. trams (0.67 V/m vs. 0.21 and 0.41 in trams in Basel and Ghent), whereas mobile phone base station exposure was lower in metros than in trams (0.16 V/m vs. 0.23 and 0.27 V/m). Metros are running underground and in underground stations micro- and pico-cells are installed. Furthermore, the coverage in metros may be poor, so that the mobile devices have to emit with stronger signals.
We have hypothesized that increase of exposure levels would be most pronounced in public transports, because of the strong increase in internet use with mobile phones after the introduction of smart phones. However, this was not the case. Over all public transports combined, temporal trends did not reach statistical significance in all three cities. Lack of significance is partly explained by the higher data variability from handset exposure, which has resulted in larger confidence intervals. The lower increase on the relative scale is probably the consequence of higher exposure levels in public transports. Thus, the increase on the absolute scale is actually higher for many public transports compared to outdoor areas. For instance the observed (significant) 63.7% increase in geometric mean in the central residential area of Basel corresponds to an increase of 0.16 V/m whereas the (non-significant) 39% increase in trains in Brussels corresponds to 1.01 V/m. A further issue which may appear contradictory is the increase of exposure from mobile phone base stations and a decrease of exposure from mobile phone handsets at the airport since there is an interaction between up- and downlink exposure. However, this interaction is complex and it has been demonstrated that the higher are the exposure levels from the base station, the lower is the output power of mobile phones (Yuanyuan et al., 2014 and Aerts et al., 2013). Further, one has to be aware that RF-EMF exposure decreases rapidly with increasing distance and thus, walking through a waiting hall at the airport will not capture uplink exposure from all emitting mobile devices in the considered area.
It is difficult to predict how RF-EMF exposure will further change over time. Assuming a linear trend of increase in RF-EMF exposure, it might be reasonable to argue that exposure will exceed regulatory limits somewhere in the future. However, along with the increase of new telecommunication devices, technologies became also more efficient in reducing emission characteristics of mobile phones. Our results suggest that the increase in number and amount of mobile phone users has not been compensated with more efficient technologies and the net effect is an increase in exposure levels for most microenvironments. Also the output power of mobile phones is affected by the technology. For example second generation mobile phones (2G, GSM) use a power control, radiating with full intensity during connection establishment and down-regulate as soon as a call has been established (Lönn et al., 2004). Smartphones of the third generation (3G, UMTS) in contrast, have a so-called enhanced adaptive power control which optimizes radiation according to the quality of connectivity to the mobile phone base station, resulting in considerable lower average output power (Gati et al., 2009, Persson et al., 2011 and Wiart et al., 2000), which may also affect overall RF-EMF exposure.
Our study offers for the first time a diligent comparison of temporal trends during a year between countries as it based on a common measurement protocol applied in all cities. We could consistently demonstrate that all exposure levels were far below reference levels proposed by ICNIRP (International Commission on Non-Ionizing Radiation Protection). Exposure levels were of the same order of magnitude in all cities. Consistently in all cities, exposure was highest in public transports (train) and lowest in residential areas (central and non-central residential areas). We found substantial increase of exposure levels for most microenvironments. It is crucial to further monitor the exposure situation in different environments in order to examine if and how exposure changes over time and to anticipate critical areas.
The authors declare no conflict of interest.