Electromagnetic Exposure Research Articles

Genetic Algorithm for TMS Coil Position Optimization in Stroke Treatment.

Transcranial magnetic stimulation (TMS), a non-invasive technique to stimulate human brain, has been widely used in stroke treatment for its capability of regulating synaptic plasticity and promoting cortical functional reconstruction. As shown in previous studies, the high electric field (E-field) intensity around the lesion helps in the recovery of brain function, thus the spatial location and angle of coil truly matter for the significant correlation with therapeutic effect of TMS. But, the error caused by coil placement in current clinical setting is still non-negligible and a more precise coil positioning method needs to be proposed. In this study, two kinds of real brain stroke models of ischemic stroke and hemorrhagic stroke were established by inserting relative lesions into three human head models. A coil position optimization algorithm, based on the genetic algorithm (GA), was developed to search the spatial location and rotation angle of the coil in four 4 × 4 cm search domains around the lesion. It maximized the average intensity of the E-field in the voxel of interest (VOI). In this way, maximum 17.48% higher E-field intensity than that of clinical TMS stimulation was obtained. Besides, our method also shows the potential to avoid unnecessary exposure to the non-target regions. The proposed algorithm was verified to provide an optimal position after nine iterations and displayed good robustness for coil location optimization between different stroke models. To conclude, the optimized spatial location and rotation angle of the coil for TMS stroke treatment could be obtained through our algorithm, reducing the intensity and duration of human electromagnetic exposure and presenting a significant therapeutic potential of TMS for stroke.

Assessing the biological effects of microwave irradiation on human semen in vitro and determining the role of seminal plasma polyamines in this process.

The aim of the present study was to investigate the influence of millimeter-wave electromagnetic (MW) irradiation on normal and pathological human sperm in vitro, and to evaluate a possible role of polyamines (PA) in this process. The stability of sperm membranes, the number of apoptotic gametes, and the content of seminal plasma PA in the ejaculates of fertile and subfertile men were compared before and after short-term MW electromagnetic exposure in vitro. The ejaculate samples were collected from healthy donors [n=25, age 22-38 years old (y.o.), average age 30.6±1.1 y.o. (mean ± SEM)] and from subfertile men (n=78, age 25-48 y.o., average age 34.1±0.8 y.o.) and exposed to MW radiation. The electromagnetic field had a wavelength of 7.1 mm, a frequency of 42.194 GHz and an exposure time of 20 min. The fragility of sperm membranes was evaluated by their resistance to sodium chloride solution (Milovanov test) and to acetic acid (Joel test). Acrosin activity was assayed spectrophotometrically. Apoptosis was determined by the externalization of phosphatidylserine on the outer side of the sperm membrane and propidium iodide staining. The PA levels were determined by agar gel electrophoretic fractionation. An increase in the resistance of sperm membranes, a decrease in acrosin activity, a decrease in the number of apoptotic gametes and a decrease in the seminal plasma PA concentrations were found after exposure of the native human sperm to low-intensity MW irradiation. Two types of reactions were revealed for the subfertile samples. The results revealed positive bio-effects of specific microwaves on the human semen and the participation of PA in the realization of these effects.

Healthy disorders by WLAN-exposure

By a diagnostic routine of a “burn-out”-patient, additionally claiming an electrosensitivity, there was tested the activity of the autonomic nervous system by electromyogram (EMG). Analyzing the frequency we found an artificial 10 Hz-component like those of WLAN-emitters as a dominant signal. By the following anamnestic discussion, the patient told about a longtime exposure to an active WLAN-equipment in office. Testing other patients using this communication-technique, there was a great number with the same 10 Hz-artifact in EMG. Additionally, some of these patients point out an artificial ECG. Theses data demonstrate the conflicts with the ICNIRP safety guidelines for this type of electromagnetic exposures.

Numerical Evaluation of Human Body Near Field Exposure to a Vehicular Antenna for Military Applications.

BackgroundThe use of electromagnetic (EM) technologies for military applications is gaining increasing interest to satisfy different operational needs, such as improving battlefield communications or jamming counterpart's signals. This is achieved by the use of high-power EM waves in several frequency bands (e.g., HF, VHF, and UHF). When considering military vehicles, several antennas are present in close proximity to the crew personnel, which are thus potentially exposed to high EM fields.MethodsA typical exposure scenario was reproduced numerically to evaluate the EM exposure of the human body in the presence of an HF vehicular antenna (2–30 MHz). The antenna was modeled as a monopole connected to a 3D polygonal structure representing the vehicle. Both the EM field levels in the absence and in the presence of the human body and also the specific absorption rate (SAR) values were calculated. The presence of the operator, partially standing outside the vehicle, was simulated with the virtual human body model Duke (Virtual Population, V.3). Several exposure scenarios were considered. The presence of a protective helmet was modeled as well.ResultsIn the area usually occupied by the personnel, E-field intensity radiated by the antenna can reach values above the limits settled by international safety guidelines. Nevertheless, local SAR values induced inside the human body reached a maximum value of 14 mW/kg, leading to whole-body averaged and 10-g averaged SAR values well below the corresponding limits.ConclusionA complex and realistic near-field exposure scenario of the crew of a military vehicle was simulated. The obtained E-field values radiated in the free space by a HF vehicular antenna may reach values above the safety guidelines reference levels. Such values are not necessarily meaningful for the exposed subject. Indeed, SAR and E-field values induced inside the body remain well below safety limits.

Role-Playing Games as a Strategy to Incorporate Social Skills in Electrical Engineering Programs [Education Corner

Traditionally, engineering degree programs are reasonably good at transmitting technical knowledge to their students; regardless of the particular conditions of each university, lecturers usually have extensive experience in doing so. However, employers are demanding soft skills in addition to the abilities our engineers master, and strategies used to incorporate them within our compact and information-packed programs are required. This article presents an experience in promoting skills for communicating and interacting with ordinary people in technical issues, performed among electrical engineering students from the radio-frequency (RF) branch. Our proposal is to use role-playing techniques to train students to communicate with people who are afraid of electromagnetic (EM) exposure effects, which has immediate implications during 5G network deployment. Moreover, the use of forum facilities in e-learning platforms allows such techniques to be integrated within an online course.

No Alteration Between Intrinsic Connectivity Networks by a Pilot Study on Localized Exposure to the Fourth-Generation Wireless Communication Signals.

Neurophysiological effect of human exposure to radiofrequency signals has attracted considerable attention, which was claimed to have an association with a series of clinical symptoms. A few investigations have been conducted on alteration of brain functions, yet no known research focused on intrinsic connectivity networks, an attribute that may relate to some behavioral functions. To investigate the exposure effect on functional connectivity between intrinsic connectivity networks, we conducted experiments with seventeen participants experiencing localized head exposure to real and sham time-division long-term evolution signal for 30 min. The resting-state functional magnetic resonance imaging data were collected before and after exposure, respectively. Group-level independent component analysis was used to decompose networks of interest. Three states were clustered, which can reflect different cognitive conditions. Dynamic connectivity as well as conventional connectivity between networks per state were computed and followed by paired sample t-tests. Results showed that there was no statistical difference in static or dynamic functional network connectivity in both real and sham exposure conditions, and pointed out that the impact of short-term electromagnetic exposure was undetected at the ICNs level. The specific brain parcellations and metrics used in the study may lead to different results on brain modulation.

Izloženost učenika srednje elektrotehničke škole "Nikola Tesla" bežičnom elektromagnetnom zračenju

Introduction/Aim: Wireless electromagnetic radiation from routers is an everyday occurrence in the life and work of modern man. They are widely used in many professional, public and domestic facilities, which means that people of all ages can be constantly exposed to electromagnetic radiation from these devices. The aim of this study was to determine the electric field strength, the magnetic field strength, and the electromagnetic exposure of students in different laboratories of the Secondary School "Nikola Tesla", depending on the type of routers installed in them, as well as to check some of the obtained results with the help of the appropriate software program of high-frequency (High-Frequency Simulation Software - HFFSS) for the simulation of electromagnetic radiation through different environments. Methods: Measurements of electric and magnetic field strength, as well as electromagnetic exposure, were carried out using the measuring instrument Spectran HF 60105, on four different types of routers installed in four laboratories of the Secondary School of Electrical Engineering "Nikola Tesla" in Niš. Measurements were realized on each router, through five horizontal and five vertical positions, with a distance of 45o in relation to the horizontal and normal axis of the router, and with spaces of 1 cm, which gives a total number of one thousand measurements. Results: The measured results obtained on four different routers that operated at a frequency of 2.4 GHz for the electric field strength (measured in millivolts per meter), magnetic field strength (measured in microampere per meter) and electromagnetic exposure (in microWatts per square centimeter) were below the limit values defined by standards. The achieved results were verified only for the router TL-WR841HP with the help of HFSS for the simulation of electromagnetic radiation through different environments. The result of the simulation check practically confirms the reliability of the measured results for TL-WR841HP router. Conclusion: Measuring and monitoring electromagnetic radiation is a very important task aimed at preserving and improving the quality of the working and living environment, as well as the quality of life and health of people and children. Software programs for the simulation of electromagnetic radiation can be used when it is not possible to carry out experimental measurements due to technical problems, hindered access to the device, danger of excessive radiation or some other reasons.

Results of risk assessment for occupational electromagnetic exposures

In 2016, a Hungarian law was introduced in accordance with the valid guidelines of the European Parliament related to the occupational exposures of electromagnetic fields. By this law, it is mandatory to evaluate and assess all the risks of operating equipment with voltage levels above 100 kV or currents above 100 A in the industry. Based on this guideline, experts of Group of High Voltage Technology and Equipment of Budapest University of Technology and Economics have performed several risk assessments based on the prescribed requirements.In several cases, exposures of electric, magnetic and electromagnetics fields have exceeded their limits: not only in case of worst-case simulations, but during on-site measurements, measured range of electric field and magnetic flux density was in the range which requires additional protection. To reduce risks to acceptable levels, practically applicable ways of protection must be prescribed to guarantee the requested level of safety, like improved medical examinations, restriction of approach or additional personal protective gears. Based on the results, industrial processes were modified, best practices have been declared, and critical activities were reported for the government – as requested by the guideline. The main aim of the introduction of these results is to highlight the importance of this topic, to assess the so-called “invisible” sources of dangers which are unfortunately often neglected. It is also crucial to introduce the basics and typical ranges of electromagnetic exposures for the employees of the affected facilities. Education, as a second step, is also an important part of this job. This paper summarizes the typical scenarios and magnitudes of exposures in case of occupational applications. Key data of analysis and basis of risk assessment was the measured electric field and magnetic flux density values compared to the current limits prescribed in the territory of the EU.

Health Effects of 5G Base Station Exposure: A Systematic Review

The Fifth Generation (5G) communication technology will deliver faster data speeds and support numerous new applications such as virtual and augmented reality. The additional need for a larger number of 5G base stations has sparked widespread public concerns about their possible negative health impacts. This review analyzes the latest research on electromagnetic exposure on humans, with particular attention to its effect on cognitive performance, well-being, physiological parameters, and Electroencephalography (EEG). While most of their results indicated no changes in cognitive function, physiological parameters, or overall well-being, the strength of the EEG alpha wave is noticed to vary depending on various aspects of cognitive functions. However, the available studies have not investigated the health effects resulting from exposure from the 5G mobile phone and base station antennas from 700 MHz to 30 GHz on the cognitive performance, well-being subjective symptoms, human physiological parameters, and EEG of adults. There is a need for such research regarding this current emerging technology. Such studies are significant in determining whether 5G technology is indeed safe for humans.

The Effect of Fluence on Neutrophil Kinetics in Zebrafish Wounds Using Real-time In Vivo Imaging

Background: Neutrophils participate in a cooperative defense strategy with macrophages following tissue injury. Application of low dose electromagnetic radiation via 635 nm wavelength can enhance macrophage recruitment to the wound, decrease tissue levels of ROS and speed healing. The impact of this wavelength on neutrophil activity in vivo is not well-described. Given that wound healing can be enhanced if collateral damage by neutrophils within the wound is decreased, we investigated how neutrophil kinetics changed during these accelerated reparative responses. Methods: Zebrafish, transgenic for the fluorescent neutrophil marker, mpx-dendra2, underwent defined fin tissue injury, and were randomized to one of two laser treatment groups, 3 J/cm2 (n=57), or 18 J/cm2 (n=69) or to the control group, 0 J/cm2 (n=164). Electromagnetic wave exposures were administered by a 635-nm continuous 5mW He:Ne laser with recipients randomized by dose delivered. Fish were three-dimensionally time-lapse imaged 30-120 minutes post injury (mpi) and wound healing documented at 24 hours post-injury. Individual neutrophil movement was tracked according to distance from wound center. Results: The lower treatment fluence, 3 J/cm2, significantly decreased neutrophil migration speed into the wound, increased reverse migration, and promoted stasis outside the adjacent wound area when compared to control and higher energy doses. The 3 J/cm2 treatment groups also exhibited more rapid wound closure when compared to control or higher fluence. Conclusions: Unlike our previous work in macrophages in which low fluence treatment enhanced the speed of forward directed migration into the wound, the response of neutrophils was decreased speed into the wound, increased reverse migration, and stasis outside the areas of the wound edges. These findings advance the notion that low fluence treatments reduce neutrophil inflammatory responses within the wound by their reduced presence within the wound. Reduced neutrophil-mediated collateral damage may work in concert with enhanced macrophage wound activity to promote faster wound healing.

Comparison of electromagnetic exposure to child and adult from electric vehicle wireless power transmission

Comparison of electromagnetic exposure to child and adult from electric vehicle wireless power transmission

Low p-SYN1 (Ser-553) Expression Leads to Abnormal Neurotransmitter Release of GABA Induced by Up-Regulated Cdk5 after Microwave Exposure: Insights on Protection and Treatment of Microwave-Induced Cognitive Dysfunction.

With the wide application of microwave technology, concerns about its health impact have arisen. The signal transmission mode of the central nervous system and neurons make it particularly sensitive to electromagnetic exposure. It has been reported that abnormal release of amino acid neurotransmitters is mediated by alteration of p-SYN1 after microwave exposure, which results in cognitive dysfunction. As the phosphorylation of SYN1 is regulated by different kinases, in this study we explored the regulatory mechanisms of SYN1 fluctuations following microwave exposure and its subsequent effect on GABA release, aiming to provide clues on the mechanism of cognitive impairment caused by microwave exposure. In vivo studies with Timm and H&E staining were adopted and the results showed abnormality in synapse formation and neuronal structure, explaining the previously-described deficiency in cognitive ability caused by microwave exposure. The observed alterations in SYN1 level, combined with the results of earlier studies, indicate that SYN1 and its phosphorylation status (ser-553 and ser62/67) may play a role in the abnormal release of neurotransmitters. Thus, the role of Cdk5, the upstream kinase regulating the formation of p-SYN1 (ser-553), as well as that of MEK, the regulator of p-SYN1 (ser-62/67), were investigated both in vivo and in vitro. The results showed that Cdk5 was a negative regulator of p-SYN1 (ser-553) and that its up-regulation caused a decrease in GABA release by reducing p-SYN1 (ser-553). While further exploration still needed to elaborate the role of p-SYN1 (ser-62/67) for neurotransmitter release, MEK inhibition had was no impact on p-Erk or p-SYN1 (ser-62/67) after microwave exposure. In conclusion, the decrease of p-SYN1 (ser-553) may result in abnormalities in vesicular anchoring and GABA release, which is caused by increased Cdk5 regulated through Calpain-p25 pathway after 30 mW/cm2 microwave exposure. This study provided a potential new strategy for the prevention and treatment of microwave-induced cognitive dysfunction.

Electromagnetic Exposure of Personnel Involved in Cardiac MRI Examinations in 1.5T, 3T and 7T Scanners.

(1) Background: It has been hypothesised that a significant increase in the use of cardiac magnetic resonance (CMR), for example, when examining COVID-19 convalescents using magnetic resonance imaging (MRI), has an influence the exposure profiles of medical personnel to static magnetic fields (STmf). (2) Methods: Static exposure to STmf (SEmf) was recorded during activities that modelled performing CMR by radiographers. The motion-induced time variability of that exposure (TVEmf) was calculated from SEmf samples. The results were compared with: (i) labour law requirements; (ii) the distribution of vertigo perception probability near MRI magnets; and (iii) the exposure profile when actually performing a head MRI. (3) Results: The exposure profiles of personnel managing 42 CMR scans (modelled using medium (1.5T), high (3T) and ultrahigh (7T) field scanners) were significantly different than when managing a head MRI. The majority of SEmf and TVEmf samples (up to the 95th percentile) were at low vertigo perception probability (SEmf < 500 mT, TVEmf < 600 mT/s), but a small fraction were at medium/high levels; (4) Conclusion: Even under the “normal working conditions” defined for SEmf (STmf < 2T) by labour legislation (Directive 2013/35/EC), increased CMR usage increases vertigo-related hazards experienced by MRI personnel (a re-evaluation of electromagnetic safety hazards is suggested in the case of these or similar changes in work organisation).

Investigation of dielectric heating method of zinc-containing materials for chlorides removal

The technological development of the world community makes it necessary to resolve the issues of the produced industrial residues utilization. Worn-out galvanized metal cars, ceilings and other metal structures require orderly utilization. Utilization of galvanized scrap may be carried out in Electric Arc Furnaces (EAF) to obtain intermediate steel and EAF dust. Electric Arc Furnaces dus contains zinc, so it is used as a secondary raw material for the production of metallic zinc. Waelz oxides are formed in Waelz kilns, after the primary processing of EAF dust. Waelz oxide contains halides that must be removed first. Halides may be removed by heating to temperatures of about 1000°C. Dielectric (microwave) heating is a promising and environmentally friendly method for material processing. Microwave heating is carried out without burning natural gas, which leads to decrease of waste gases volume. The work experimentally confirmed the possibility of zinc-containing materials heating at electromagnetic emission exposure. The duration of products heating up to the temperature of 1000°C was 128 - 188 s. The residual content of chloride ions in the calcined products is less than 0.05 wt%.

A CASE STUDY OF ELECTROMAGNETIC EXPOSURE FOR HIGH TENSION POWER LINES AND TRANSFORMER WITH AND WITHOUT BASE STATION ANTENNA

With the fast growth of electric activity and the spreading out of town scale, our lives are approached by extremely high voltage power transmission lines. And with the expansion of ultra-high voltage power transmission line, the ultra-high voltage transformer substation will come out in the place with intense inhabitants and the electromagnetic exposure of this transmission and transformer apparatus and its contamination to the inhabitants stimulate the immense anxiety from the civilization. This paper deals with electromagnetic radiation of extremely high voltage power transmission line. Here we have observed the electric and magnetic field beneath the transmission line by the process of equivalent charges and put forward the anticipation rule to the electromagnetic radiation in the engineering of extremely high voltage power dissemination and remodeling. Recognition the safe distance from the EMF produced from the high-tension overhead power lines in the locality of the precise region is the detailed goal of this study. The high-tension transmission lines generated EMF that bounded the projected site has to be underneath 0.2 µT. The safety approval distance has been allotted as 200 m from the active 300-KV high-tension power line.

Investigation of Electromagnetic Exposure of WPT Coil to Human Body Based on Biological Electromagnetic Safety Assessment

When the wireless power transmission (WPT) system of electric vehicle(EV) is working, the leakage of high frequency electromagnetic field (EMF) to the non-working area will be threaten to human safety. According to SAE J2954 standard, the coupling coils modeling of WPT and car shell modeling are established. WPT's bit-directional guidance technology and deviation correction control strategy are given. According to the harm degree of SAR, power density P, current density J and magnetic induction intensity B to human body when the human model is in different positions of standing, lying and sitting, the comprehensive harm index of electromagnetic radiation Σhurt is creatively proposed to assess the electromagnetic radiation hazard of EV. Field circuit co-simulation helps us to study the bio-electromagnetic safety of WPT in vehicle environment. A human exposure EMF joint test system is designed and made to measure vehicle’s surrounding EMF. Through simulation and experimental verification, WPT coil’s electromagnetic exposure level to the human body inside the EV meets the requirements of ICNIRP, the EMF at the ankle outside the EV exceeds the standard and needs to be protected.

Mathematical Model Optimization Techniques under Unreliable Electromagnetic Field for ECG Waves

The electrocardiogram (ECG) has significant scientific importance for analyzing the majority of cardiovascular diseases. On one side the technologies are growing very fast, on the other side there is a need to check and balance their effect on human health. The activity of the heart ECG voltage vector is well explained by the modeling of the ECG wave. It is one of the essential tools to do so. In the proposed work we tried to elucidate a mathematical model for the ECG wave by presumptuous the human body as a cylindrical complex dielectric and conducting medium. The human heart is considered as a harmonic bio-signal generator positioned in this medium. Nowadays, technologies are enhancing in various aspects as the graph of mobile phone users increasing rapidly day by day. Essentially, it needed to understand its side effects on the human body and especially for the health of the human heart. The electrical equivalent of the heart can be used to develop a mathematical model for the human heart as per its functioning. The ECG parameters which are affecting due to the electromagnetic wave can be analyzed using a proposed mathematical model. If mathematical expressions are available relations can be formed and understand for each part of the human heart. As mobile phone and its, some component gives electromagnetic exposure to the human body. Hence there is a need to develop a model of the human heart using mathematical analysis. Hence, this paper proposes a mathematical model for ECG and variation of parameters due to electromagnetic field- based.

Exposure to toxic occupations and their association with Parkinson's disease: a systematic review with meta-analysis.

Earlier longitudinal reviews on environmental and occupational toxins and Parkinson's disease (PD) risk have limitations. This study aimed to determine the strength of association between three types of toxic occupational exposures and the occurrence of PD by diagnostic methods. A search was conducted of EMBASE, PubMed/Medline, Toxnet, LILACS, and Cochrane Library databases for longitudinal studies that assessed toxic occupational exposure, Parkinsonian, or related disorders, diagnosed by International Classification of Diseases (ICD) codes, medical records, or confirmation by a neurologist/nurse, and published in the English language from January 1990 to July 2021. Pooled risk ratios (RR) estimates were produced using random-effects models. Systematic review with meta-analysis synthesized the results. Study quality, heterogeneity, and publication bias were examined. High-quality articles that met the inclusion criteria were analyzed. Twenty-four articles were used in the analyses. The pooled RR for electromagnetic exposure and PD were (RR=1.03, 95% confidence interval [CI] 0.91-1.16) while the pooled RR between PD and metal and pesticide exposure were (RR=1.07, 95% CI 0.92-1.24) and (RR=1.41, 95% CI 1.20-1.65), respectively. Pooled RR for methods of diagnosis and their associations with PD were: confirmation by a neurologist or nurse (RR=2.17, 95% CI 1.32-3.54); ICD codes (RR=1.14, 95% CI 1.03-1.26), and medical records (RR=1.06, 95% CI 0.92-1.21). Our systematic review provides robust evidence that toxic occupational exposures are significant risk factors for PD especially those diagnosed by neurologists or nurses using standardized methods.

Effects of massive electromagnetic pulses on the structural and chemical properties and leaching efficiency of eudialyte concentrate

Scanning electron microscopy (SEM) and infrared spectroscopy (IR) were used to study the influence of high-power nanosecond electromagnetic pulses (HPEMP) and dielectric barrier discharges (DBD) in air at the atmospheric pressure on the structural and chemical properties of eudialyte. The spectral data analysis has shown that highintensity electric fields initiate mineral surface fracturing due to the weakening and/or breaking of bonds in the structural fragments of the mineral framework (presumably, Si10O27, and Si9MO30). According to the SEM data, HPEMPs cause sample surface strength reduction with the formation of new surface reliefs in the range from parallel (texp = 30 s) to polygonal fractured shapes (texp = 60 and 90 s), depending on the electromagnetic pulse exposure time texp. Eudialyte grain micromorphology after the treatment under DBD conditions is distinctively characterized by the presence of imprints of electrical current breakdown microchannels of up to 3&ndash;4 &mu;m, with practically no microcracks or other defects occurring on the mineral surface. The intensifying effect of high-power electromagnetic pulses on the process of eudialyte concentrate acid leaching has been experimentally established. Zirconium recovery into the pregnant solution is improved by 3.4 to 4.3 % through HPEMP pretreatment and by 4.0 % through DBD exposure, with the total recovery of rare earth elements increasing by 1.1 to 1.7 %.This work was financially supported by the Ministry of Science and Higher Education of the Russian Federation, project No. 13.1902.21.0018 (agreement No. 075-15-2020-802).

Electromagnetic Exposure Dosimetry Study on Two Free Rats at 1.8 GHz via Numerical Simulation.

Normally, the impact of electromagnetic exposure on human health is evaluated by animal study. The biological effect caused by electromagnetic exposure on such experimental animals as rats has been proven to be dose-dependent. However, though the dose of radio frequency (RF) electromagnetic exposure described by the specific absorbing rate (SAR) on fixed rats has been relatively well-studied utilizing the numerical simulations, the dosimetry study of exposure on free rat is insufficient, especially in the cases of two or more free rats. Therefore, the present work focuses on the variation of SAR caused by the existence of neighboring free rat in the same cage. Here, infrared thermography was used to record the activity of the two free rats who lived in the same cage that mounted at the far-field region in the microwave darkroom for a duration of 48 h. Then, using image processing techniques, the relative positions and orientations of the two rats are identified, which are defined by three parameters, such as the relative distance (d), relative direction angle (α), and relative orientation angle (β). Using the simulation software XFdtd 7.3, the influence of d, α, and β on the whole-body average SAR (WB-avgSAR) of the rats exposed to 1.8 GHz electromagnetic wave was calculated and analyzed. Then, the average variation of WB-avgSAR of the two rats compared with that of a single rat within 48 h was calculated. The numerical simulation results showed that the relative posture position described by (d, α, and β) of the two rats affects their WB-avgSAR and leads to fluctuations at different positions. However, the variation rate of the 48-h-average WB-avgSAR was only 10.3%, which implied that the over-time average SAR of two or more rats can be roughly described by the WB-avgSAR of a single free rat, except when a real-time precise control of exposure dose is necessary.