This paper reports the electromagnetic field (EMF) exposure levels from fifth generation (5G) services. Three mobile operators in South Korea launched the world's first 5G New Radio networks using the 3.5 GHz band in April 2019. The transmitted power of the uplink slots and the synchronization signal reference signal received power (SS-RSRP) from user equipment (UE) were measured in Seoul. The power samples, averaged over a 1-s duration, were obtained for a traffic period of approximately 270 h from October 2019 to early February 2020 using the file transfer protocol while driving along the side streets in residential areas of Seoul. The measurement results show that the time-average level when exposed to a beam sweep of the base stations was less than 5 µW/m 2 . However, the UE transmitted power level approached the maximum for a considerable period of the total measurement time owing to the extremely low SS-RSRP level of the base stations.

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The US National Toxicology Program (NTP) conducted a long-term carcinogenic and toxicity study with small animals on the effects of mobile phone radiation at 900 MHz and 1900 MHz, respectively, and showed an increase in incidence of malignant schwannomas in the heart of male rats at very higher exposure levels. To verify and clarify the NTP study results, Japan and Korea are conducting a joint study using the same reverberation chamber type exposure system as in the NTP study. The purpose of this paper is to derive a quantitative relationship between the electric field strength in the reverberation chamber and the exposure level, i.e., the mean whole-body averaged specific absorption rate (WBA _ SAR) of rats based on a large-scale finite difference time domain (FDTD) simulation. First, two FDTD simulation methods, one with a single plane wave incidence and the other with simultaneous plane wave incidence, were compared, and then the former method was adopted for convenience and saving calculation time. The derived quantitative relationship between the WBA _ SAR and the electric field strength required to achieve the WBA _ SAR consists of a one-dimensional approximation model which considers only the body mass of rats and a twodimensional approximation model which considers not only the body mass but also the number of rats. The two approximation models cover the entire two-year exposure period, and the exposure level in the two-year long-term exposure experiment is being well controlled. Moreover, unlike dosimetry in the NTP study, an uncertainty analysis of numerical dosimetry was performed in more details, and the combined standard uncertainty in the WBA _ SAR was found to be 16.1%.

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As the skin is the largest body organ and critically serves as a barrier, it is frequently exposed and could be physiologically affected by radiofrequency electromagnetic field (RF-EMF) exposure. In this study, we found that 1760 MHz RF-EMF (4.0 W/kg specific absorption rate for 2 h/day during 4 days) exposure could induce intracellular reactive oxygen species (ROS) production in HaCaT human keratinocytes using 2′,7′-dichlorofluorescin diacetate fluorescent probe analysis. However, cell growth and viability were unaffected by RF-EMF exposure. Since oxidative stress in the skin greatly influences the skin-aging process, we analyzed the skin senescence-related factors activated by ROS generation. Matrix metalloproteinases 1, 3, and 7 (MMP1, MMP3, and MMP7), the main skin wrinkle-related proteins, were significantly increased in HaCaT cells after RF-EMF exposure. Additionally, the gelatinolytic activities of secreted MMP2 and MMP9 were also increased by RF-EMF exposure. FoxO3a (Ser318/321) and ERK1/2 (Thr 202/Tyr 204) phosphorylation levels were significantly increased by RF-EMF exposure. However, Bcl2 and Bax expression levels were not significantly changed, indicating that the apoptotic pathway was not activated in keratinocytes following RF-EMF exposure. In summary, our findings show that exposure to 1760 MHz RF-EMF induces ROS generation, leading to MMP activation and FoxO3a and ERK1/2 phosphorylation. These data suggest that RF-EMF exposure induces cellular senescence of skin cells through ROS induction in HaCaT human keratinocytes.