Human Electromagnetic Field Exposure in Wearable Communications: A Review <s> Fig. 1: A typical setup of DASY <s> During an MR procedure, most of the transmitted RF power is transformed into heat within the patient's tissue as a result of resistive losses. Not surprisingly, the primary bioeffects associated with the RF radiation used for MR procedures are directly related to the thermogenic qualities of this electromagnetic field. This review article discusses the characteristics of RF energy-induced heating associated with MR procedures, with an emphasis on thermal and other physiologic responses observed in human subjects. <s> BIB001 </s> Human Electromagnetic Field Exposure in Wearable Communications: A Review <s> Fig. 1: A typical setup of DASY <s> Protocols and test procedures are specified for the measurement of the peak spatial-average SAR induced inside a simplified model of the head of users of certain handheld radio transceivers. These transceivers are intended to be used for personal wireless communications services, operate in the 300 MHz to 6 GHz frequency range, and are intended to be operated while held against the ear. The results obtained by following the protocols specified in this recommended practice represent a conservative estimate of the peak spatial-average SAR induced in the head of a significant majority of persons, subject to measurement and other uncertainties that are defined in this recommended practice. The results are representative of those expected during conditions of intended use of a handheld wireless device. It is not the intent of this recommended practice to provide a result representative of the absolute maximum SAR value possible under every conceivable combination of head size, head shape, handset orientation, and spacing relative to the head. The measurement of SAR induced in the external tissues of the head, e.g., the external ear (pinna), is not addressed in this document. This recommended practice also does not address the body SAR measurements typically required for wireless handsets. The following items are described in detail: measurement concepts, measurement techniques, instruments, calibration techniques, simulated-tissue (phantom) models, including homogeneous anatomically equivalent models of the human head and simple phantoms for validation of the SAR measurement system, and the limitations of these systems when used for measuring the spatial-peak mass-averaged SAR. Procedures for calibrating electric field (E-field) probes used for SAR measurements and assessing the SAR measurementand system uncertainties are provided in the annexes. This recommended practice is intended primarily for use by engineers and other specialists who are familiar with electromagnetic (EM) theory and SAR measurement techniques; it does not recommend specific SAR limit values since these are found in other documents. The benefits to the users include standardized and accepted protocols, validation techniques, and means for estimating the overall measurement uncertainty in order to produce valid and repeatable data. <s> BIB002 </s> Human Electromagnetic Field Exposure in Wearable Communications: A Review <s> Fig. 1: A typical setup of DASY <s> Effect of 1.8 GHz radiofrequency electromagnetic radiation on novel object associative recognition memory in mice <s> BIB003
2) Measurement of Time-Averaged SAR: In a DASY, a time-averaged SAR is calculated by specifying the device dimensions first in the project setup  . Next, the phantom section, test distance, the position of the device under test (DUT), and communications system are specified. The area scan and zoom scan are performed accordingly. The duration of the scan is specified in the scan duration field. The default value is 6 minutes, compliant with the current safety guideline  . A typical measurement procedure can be summarized as follows BIB002 : • SAR Reference Measurement: Before a time-average SAR test, a local SAR is measured at a stationary reference point where the SAR exceeds the lower detection limit of the measurement system. • Area Scan: Once a reference is found, it is necessary to determine peak SAR positions. An electric field probe moves through the tissue-equivalent liquid in a specific anthropomorphic mannequin (SAM) or a flat phantom to find the approximate location of the SAR peak. The distance between the phantom and the probe has to be more than half the probe diameter; otherwise, the peak SAR is measured at a higher value than actual and in turn the uncertainty is increased. The measured values are interpolated to determine peak locations. The rationale of the interpolation is that a sensor behind a probe tip is usually not able to measure a local peak SAR occurring at the surface of homogeneous phantoms  . • Zoom Scan: The goal of a zoom scan is to determine cube averaged SAR. Zoom scans surrounding one or more of these peak locations are performed to finally determine the value of a peak spatial-average SAR. 3) Controversy: In the design of a SAR measurement method, the main challenge is how to efficiently mock the human body in a test setup. The reason is that it is difficult to account for the numerous critical variables affecting the test responses-i.e., the subject's age, the amount of subcutaneous fat, the physical condition of the individual, etc BIB001 . This complexity has been noted recently in practice. It is claimed that the current SAR measurement methodology is not general enough to "represent" the diverse characteristics of a human body  . The methodology was developed in 1989 and the dummy head, which is used for the measurements, is equivalent to that of a 6 feet 2-inch person weighing 220 pounds. The human brain is represented by a simple mixture of water and electrolytes, and the massive head is subjected to only 6 minutes of peak activity before taking the measurements. Although these are only some of the issues of the test, they are enough to show that it may not represent an average person's usage in 2019. The similar inefficiency occurs when a measurement is conducted using animal subjects. Previous studies have produced conflicting evidence regarding the health effects of exposure to EMF due to methodological differences in experimental setups, exposure durations, the animal models used, and the behavioral test(s) used to asses learning and/or memory BIB003 .