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With the rapid development of modern communication technology, the widespread deployment of 5G technology has increased the level of electromagnetic field (EMF) exposure in people’s daily lives. Although a large number of studies have explored the effects of electromagnetic radiation on biological organisms, these studies often focus on short-term exposure effects and neglect the impact of long-term exposure.
On December 26, 2023, a team from National Research Tomsk State University published an article titled “Estimation of SAR Average in Rats during 5G NR Chronic Exposure” in Applied Sciences. To address the aforementioned issues, the article aims to study the whole-body SAR of rats under simulated radiation from 5G new radio base stations, providing a method for assessing the biological effects of electromagnetic radiation.
Original Information:
Estimation of SAR Average in Rats during 5G NR Chronic Exposure
Original Link:
https://www.mdpi.com/2076-3417/14/1/208
Journal Information:
Applied Sciences, IF: 2.7
Innovative Points of the Paper
The research proposed a new method for estimating SAR, which specifically considers the effect of the decrease in power flow density of electromagnetic waves (i.e., power per unit area) with increasing distance. Numerical simulations were performed using the CST Microwave Studio software package, and the results were compared with theoretical estimates to verify the effectiveness of the method. By simulating the transmission of 5G New Radio base stations, the study explored the impact of long-term electromagnetic field exposure on the changes in SAR values in rats, filling the gap in existing research.
Experimental Methods
The experiment used the Adalm Pluto SDR module to generate 5G NR signals, which were irradiated onto the rat cage through a PlastRam antenna, simulating the radiation effects of a 5G base station. The experiment was divided into different dose groups, controlling the SAR values by changing the distance and power of the antenna.
Experimental Setup: The rats were placed in a cage, one side of which was irradiated by the radiation unit, while the other side was equipped with a protective barrier (measuring 98 × 25 cm) to limit any possible external radiation. Two different radiation power levels of 0.5 W and 0.0891 W were used in the experiment to ensure that the SAR values during the experiment did not exceed the limits set by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) for whole-body SAR.
Animal Model: The experiment used male Wistar rats, divided into three groups for exposure experiments under different conditions. The first and second groups each contained 10 rats (5 per cage), while the third group contained 20 young rats (10 per cage).
Exposure Time and Distance: The first group of rats was exposed to radiation for 24 hours over a week, with the antenna located 12 cm from the cage; the second group was exposed for 4 weeks, also with the antenna 12 cm from the cage; the third group, due to their lower average weight, had the antenna placed 20 cm away from the cage to balance the SAR values.
To estimate the average SAR of the entire experimental animal population, a simplified form was used, considering the actual distribution of the experimental animals in the cage and the non-uniformity of the radiation field. Specifically, when the ratio of the animal’s body length to the wavelength (L/λ) is greater than 0.4, the average SAR can be estimated using the following formula:
The numerical simulation part was completed using the CST Microwave Studio software package. In the study, theoretical calculations and numerical simulation results were used for comparison to verify the accuracy of the theoretical model.
Experimental Results
As shown in Table 1, the numerical simulation and theoretical estimates compared SAR values for two different experimental setups (the cases of two and ten rats). For the case of two rats, the average SAR value was 0.202 W/kg, while for the case of ten rats, the average SAR value decreased to 0.0818 W/kg. This result indicates that as the number of rats in the cage increases, the overall average SAR value significantly decreases. This phenomenon may be related to the different positional distribution of the rats relative to the antenna, leading to different distributions of radiation energy on the rats. The difference between theoretical estimates and numerical simulations was 7% for non-distributed absorption (i.e., the case of two rats) and 10% for distributed absorption (i.e., the case of ten rats).
Table 1. Comparison of SAR Numerical Simulation and Theoretical Estimates.
As shown in Figure 1, the estimated distribution of SAR reveals the distribution of SAR values within the rats under different exposure conditions, especially when considering the potential effects of animal behavior and environmental reflections on SAR measurements. The results indicate that as the distance of the rats from the antenna increases, the average whole-body SAR values in the three different experimental groups showed significant decreases. Specifically, the groups represented by wbSAR1 and wbSAR2 had higher SAR values at closer distances (approximately 12 cm), with a rapid decrease in SAR values as the distance increased. The group represented by wbSAR3 began to show SAR values at a longer distance (approximately 20 cm), with a relatively slow decreasing trend. Fewer rats may lead to each rat absorbing more radiation, while in the case of more rats, each rat absorbs less radiation energy. Since the rats can move freely in the cage, they may stay close to or away from the radiation source, which will affect the distribution of SAR values within them.
Figure 1. Theoretical estimation of SAR distribution in experimental groups.
Conclusion and Outlook
This study developed an improved theoretical estimation method and experimental setup to simulate the transmission of a 5G base station to estimate the whole-body SAR of rats under long-term electromagnetic field exposure. This method considers one-sided irradiation and distributed absorption, and the accuracy of the theoretical estimation was verified by comparison with numerical simulations. The results indicate that the improved SAR estimation method is consistent with the numerical simulation results, providing an effective assessment tool for studying the biological effects of long-term electromagnetic radiation. Future research can explore the effects of different frequencies and radiation intensities on biological effects, as well as SAR estimation methods for different animal models, to gain a more comprehensive understanding of the potential impacts of electromagnetic radiation on health.
Medical Electromagnetic Community
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