Radiofrequency electromagnetic exposures during the use of wireless links of portable computers inside trains without internal WiFi services

Exposure to radiofrequency electromagnetic field (RF-EMF) emitted during the wireless exchange of data with internet services is inevitable while using portable computers. This work examines the profiles of RF-EMF exposure while using portable computers inside fast train cars without internal WiFi services, based on the frequency-selective RF-EMF measurements by portable, autonomous, radiofrequency exposure monitors (REM), EME SPY 121 type, performed during journeys over the northern part of Poland (mostly across rural areas). The profiles to RF-EMF in trains were compared with exposure in laboratory conditions where internal WiFi services are available. Our study experimentally confirmed that multi-path propagation of EMF signals used by wireless links of external wireless modems of many portable computers (usually at GSM or LTE uplink frequency bands used by public mobile phone networks operated with SIM card access) may produce significantly stronger RF-EMF exposure inside train cars without internal WiFi facilities than exposure from integrated WiFi computer modems and indoor WiFi facilities usually used by portable computers inside buildings. The results obtained suggest that the use of portable computers with external modems operating with public mobile phone networks inside train cars needs to be considered as a potential scenario for the worst case of RF-EMF exposure in safety evaluation required by European Directive 2014/53/EU (radio equipment directive - RED).