Spatially Averaged Epithelial/Absorbed Power Density for Nonplanar Skin Models Exposed to Antenna at 10-90 GHz

International guidelines and standards for human protection from electromagnetic fields have been revised recently. The epithelial/absorbed power density (APD) has been used as a new physical quantity for local exposure to frequencies > 6 GHz, related to the temperature rise in the superficial layer. The assessment methods of APD for practical exposure scenarios are crucial for realistic exposures. This study investigates averaging methods for APD in nonplanar skin models for local electromagnetic field exposure from 10 to 90 GHz. Eight research groups compared the calculated APDs using distinct numerical approaches and postprocessing techniques. The intercomparison aimed to clarify the primary causes of variations in aspects, such as APD averaging methods, skin model structure, and types of exposure antennas. Statistical analyses reveal that the maximum differences in relative confidence intervals (RCI) due to different average methods and skin models are within 9.4% and 5.1%, respectively. In contrast, when the distance between the antenna and skin is set to 5 mm, the discrepancy attributed to the exposure antenna reaches 59.4% at 10 GHz. This difference does not exceed 9.2% under other computational conditions. Additionally, the spatially averaged APD appears to have a linear relationship with the maximum skin surface temperature elevation, based on regression analysis. The findings indicate that the variances in the spatially averaged APD are largely independent of both the APD averaging methods and skin model structures. However, they slightly depend on the antenna types used as exposure sources.