## 3 Results and Discussion  
### Single Location On-Body RF-EMF Exposure Evaluation (Virtual Measurements)  
For each of the 24 considered exposure scenarios (differing in RF EMF propagation direction, E-field vector polarization and frequency), the deviation in the results of the exposure assessment by a wearable device compared to the unperturbed EMF value was assessed based on the ratio of the E-field calculated in the particular location of the  
Figure 5: The locations of three PEMs, constituting the physical model of the multi-location on-body RF EMF measurement system, on the body of the researcher taking test measurements and the view to base station antennas emitting measured EMF (red circles: the location of PEMs). modeled E-field sensor (probe) to the unperturbed E-field value, set at the level of 10 V/m in simulated exposure scenarios. The following KX ratio is a measure of the influence from the proximity of the human body on the distribution of the evaluated E-field across all 24 exposure scenarios:  
\[\text{KX}=\text{E}_{\text{x}}/\text{E}_{\text{up}}, \tag{1}\]  
where: E\({}_{\text{x}}\)--E-field value affecting location of an on-body single probe equipment; E\({}_{\text{up}}\)--the unperturbed E-field value set in the modeled exposure scenario (E\({}_{\text{up}}\) = 10 V/m). Figure 6 presents the statistical analysis of KXbp(fb) evaluated following Formula (1) for each of a single \(\phi\)50 mm E-field ball-probe (bp) location (sensor locations: H--head, C--chest, A--arm, W--waist, F--front, B--back, R--right side, L--left side), across the considered RF EMF frequencies (fb), as when evaluated using multi-channel narrowband PEM (MMR--minimum-maximum ranges and mean values). Figure 7 presents a distribution of broadband RMS value derived for each measurement location from the frequency selective results, modeling a broadband measurements following the formula:  
\[\text{KX-RMSbp}\ =\ \sqrt{\sum\text{KXbp}(\text{fb})^{2}} \tag{2}\]  
where: KXbp(fb)--KX ratio established according to Formula (1) in analysed frequency band. The largest dispersion of results (KXbp ratio), regardless of the single-point ball-probe measurement location, was obtained at the 100 MHz frequency--range from KXbp = 0.22 (for WB location) to KXbp = 3.21 (for H location). When the 100 MHz frequency, representing EMF exposure from FM radio broadcasting antennas, is excluded from the considerations, because of the limited number of location near such EMF sources, the smallest dispersion of results was found for the ball-probe measurement point located on the top of the head (H)--range from KXbp = 0.59 (for 400 MHz) to KXbp = 1.47 (for 700 MHz). However, performing measurements in real conditions with today's regular equipment placed on the top of the head, e.g., on a helmet, may not be an acceptable solution for  
Figure 6: The KXbp(fb) ratio, presenting the discrepancy between the unperturbed E-field and the results of E-field measurements by multi-channel (narrowband) wearable equipment in various locations near the human body (analyzed subsets of results over all directions of RF EMF propagation and E-field vector polarizations, when the measurement equipment is located on: H—head, C—chest, A—arm, W—waist, F—front, B—back, R—right side, L—left side); the distribution of results at a particular frequency are characterized by MMR—the range from minimum to maximum values (bar), and mean value (dot). ergonomic reasons. Wearing them for many hours during measurement sessions over an entire shift may cause significantly increased fatigue to workers whose exposure is being assessed, e.g., when the equipment weighs more than double the weight of a typical helmet of mandatory use in the work environment, i.e., 300-450 g. The weight of commercially available devices ranges from 90 to 500 g, which may make it possible to arrange measurements using PEM on the helmet (using smaller PEM is better option), even without next generation of small equipment specially designed for such measurement protocol.