## 4 Discussion
Indeed, although the data have the same order of magnitude, for arm, leg and shoulder antenna positions, the exposure was much higher for Duke than for Ella (28% for the case of the shoulder, 110.9% for the case of leg and 75.9% for the arm's case). A possible reason of the increase in the Duke's values is the greater amount of muscle in the male model with respect to the female one indeed, in this tissue, higher values of SAR\({}_{10g}\) have been detected unlike the female model. The opposite situation occurs when the antenna was posed on the torso, for which the exposure resulted higher for [PERSON] than for [PERSON] (i.e., an increase of 8.1%). To explain this evidence, SAR\({}_{10g}\) distributions have been evaluated in each tissue considered in the cubical box and it was evident that the value found in the [PERSON]'s breast gives strong contribution to the increase of the maximum value. For any configuration analyzed, the peak SAR\({}_{10g}\) was mainly located in the most external tissues. This behavior was expected with such a high frequency because of the relationship of inverse proportionality between the frequency and the penetration depth. The peak values here obtained have been compared with the ICNIRP Guidelines limits [14]. Into the guidelines, there are two different occupational limit values depending on the anatomical district category considered: for the local Head/Torso the limit is 10 W/kg and for the local limb is 20 W/kg. These values of local SAR must be considered  
Figure 5: Descriptive statistics (minimum, 25 th, 50 th, 75 th percentile and maximum) of the SAR\({}_{10g}\) distributions in the tissues included in volume of interest relative to the analyzed anatomical district: Duke and Ella, both without the steel helmet. as averaged over 6 min and over a 10-g cubic mass. The limit values were exceeded in several exposure conditions here simulated: (i) [PERSON]'s exposure when then antenna was posed on the arm, the leg, and the torso; (iii) for [PERSON]'s exposure when the antenna was posed on the torso, and (iv) when the antenna was posed on the ankle. However, it is important to underline that the input power has been here set at 1 W, which is higher than the realistic values of the power supply of the wearable antennas, which is in the order of tens of mW [21,22]. Therefore, all the peak SAR\({}_{\text{10g}}\) values should be re-scaled accordingly, resulting therefore always in compliance with the regulation. Moreover, the obtained values of the peak SAR\({}_{\text{10g}}\) are in line with the data reported in the literature. In fact, [PERSON] et al. [11] estimated the peak SAR\({}_{\text{10g}}\) to be equal to 8.16 W/kg when a simplified human arm, made of skin, fat, muscle, and bone, was exposed to the radiation emitted by a wearable antenna tuned at f = 2.4 GHz with an input power of 0.5 W. Moreover, [PERSON] et al. [4] have exposed a rectangular parallelepiped homogeneous phantom to a wearable antenna at f = 2.45 GHz and the peak SAR\({}_{\text{1g}}\) obtained for an input power of 1 W was 48 W/kg. Evaluating the average of the peak SAR\({}_{\text{1g}}\) across all the simulations here implemented (data not shown), except for the antenna positioning close to the head, resulted in a SAR\({}_{\text{1g}}\) of about 34 W/kg. Finally, [PERSON] et al. [1] have simulated an antenna tuned at f = 2.45 GHz on two heterogenous adult phantoms ([PERSON] and Ella models); the peak SAR\({}_{\text{1g}}\) obtained when the antenna was positioned on the model torso ranged from 18.7 to 30.7 W/kg for an input power of 1 W. Similarly, evaluating the peak SAR\({}_{\text{1g}}\) from our simulations when the antenna was posed on the torso for a frequency of 2.45 GHz, it ranges from 26.4 to 29.2 W/kg for 1 W of input power. However, it is noteworthy that in the interpretation of the results of EMF numerical dosimetry an intrinsic level of uncertainty, that can influence the reliability of the estimated SAR values, should be always taken into consideration.