Design and Implementation of a Specialised Millimetre-Wave Exposure System for Investigating the Radiation Effects of 5G and Future Technologies.

As the fifth-generation (5G) network is introduced in the millimetre-wave (mmWave) spectrum, and the widespread deployment of 5G standalone (SA) is approaching, it becomes essential to establish scientifically grounded exposure limits in the mmWave frequency band. To achieve this, conducting experiments at specific frequencies is crucial for obtaining reliable evidence of potential biological impacts. However, there is a literature gap where experimental research either does not utilise the mmWave high band (e.g., the 26 Gigahertz (GHz) band) or most studies mainly rely on computational approaches. Moreover, some experimental studies do not establish reproducible test environment and exposure systems. Addressing these gaps is vital for a comprehensive exploration of the biological implications associated with mmWave exposure. This study was designed to develop and implement a mmWave exposure system operating at 26 GHz. The step-by-step design and development of the system are explained. This specialised system was designed and implemented within an anechoic chamber to minimise external electromagnetic (EM) interference, creating a controlled and reproducible environment for experiments involving high-frequency EM fields. The exposure system features a 1 cm radiation spot size, enabling highly localised exposure for various biological studies. This configuration facilitates numerous dosimetry studies related to mmWave frequencies.

Pulse modulated radiofrequency exposure influences cognitive performance.

PURPOSE: To investigate whether exposure to pulse modulated radiofrequency (PM RF) influences human cognitive performance, and whether it does so in a dose-dependent manner. MATERIALS AND METHODS: Thirty-six healthy adults participated in a randomized, double-blind, counterbalanced provocation study. Cognitive performance was assessed using a visual discrimination task and a modified Sternberg working memory task, which were calibrated to individual performance levels in a preliminary testing session. An sXh920 planar exposure system was used to generate a 920 MHz GSM-like signal, providing three conditions (peak-spatial SAR averaged over 10 g) of 0 W/kg (sham), 1 W/kg (low RF) and 2 W/kg (high RF). RESULTS: A significant decrease in reaction time (RT) in the Sternberg working memory task was found during exposure compared to sham. This effect was not dose-dependent. CONCLUSIONS: Cognitive performance was shown to be faster under PM RF conditions, relative to sham, in a working memory task. While the majority of the literature has not found effects of PM RF exposure on cognitive performance, it is possible that the methodological improvements employed in the present study increased sensitivity, and thus the ability to detect potential effects.

A genotoxic analysis of the hematopoietic system after mobile phone type radiation exposure in rats.

PURPOSE: In our earlier study we reported that 900 MHz continuous wave (CW) radiofrequency radiation (RFR) exposure (2 W/kg specific absorption rate [SAR]) had no significant effect on the hematopoietic system of rats. In this paper we extend the scope of the previous study by testing for possible effects at: (i) different SAR levels; (ii) both 900 and 1800 MHz, and; (iii) both CW and pulse modulated (PM) RFR. MATERIALS AND METHODS: Excised long bones from rats were placed in medium and RFR exposed in (i) a Transverse Electromagnetic (TEM) cell or (ii) a waveguide. Finite-difference time-domain (FDTD) numerical analyses were used to estimate forward power needed to produce nominal SAR levels of 2/10 and 2.5/12.4 W/kg in the bone marrow. After exposure, the lymphoblasts were extracted and assayed for proliferation rate, and genotoxicity. RESULTS: Our data did not indicate any significant change in these end points for any combination of CW/PM exposure at 900/1800 MHz at SAR levels of nominally 2/10 W/kg or 2.5/12.4 W/kg. CONCLUSIONS: No significant changes were observed in the hematopoietic system of rats after the exposure of CW/PM wave 900 MHz/1800 MHz RF radiations at different SAR values.

Evaluation of hematopoietic system effects after in vitro radiofrequency radiation exposure in rats.

PURPOSE: This study was designed to investigate the effect of a 900-MHz continuous-wave (CW) radiofrequency radiation (RFR) exposure on the hematopoietic system in the rat. MATERIALS AND METHODS: Rat long bones (femur and tibia) were divided into two groups: Sham-exposed and radiofrequency (RF)-exposed. The mean Specific energy Absorption Rate (SAR) at 900-MHz averaged over the bone marrow (calculated by the finite-difference-time-domain ( fdtD) method) was 2 W/kg at 16.7 W root mean square (rms) forward power into a Transverse Electromagnetic (TEM) cell. The bones, placed in a Petri dish containing media, were kept in the TEM cell for 30 min duration of sham or RF exposure. After exposure, the bone marrow cells were extracted and the following end points were tested: (a) Proliferation rate of whole bone marrow cells, (b) maturation rate of erythrocytes, (c) proliferation rate of lymphocytes, and (d) DNA damage (strand breaks/alkali labile sites) of lymphocytes. RESULTS: Our data did not indicate any significant change in the proliferation rate of bone marrow cells and lymphocytes, erythrocyte maturation rate and DNA damage of lymphocytes. CONCLUSION: Our findings revealed no effect on the hematopoietic system in rats for 900 MHz CW RF exposure at the 2 W/kg localised SAR limit value recommended by the International Commission for Non-Ionising Radiation Protection (ICNIRP) for public exposures.

Predictors of mobile telephone use and exposure analysis in Australian adolescents.

AIM: Australian adolescents are increasingly using mobile telephones (MP) while the debate on MP safety persists. This group is not generally engaged in full-time employment, suggesting that their MP use is not work related. We investigated possible predictors of MP use in young people. METHODS: We assessed exposure to radiofrequency energy from MP by means of a self-administered questionnaire adapted from INTERPHONE--an international case-control study of adult brain, head and neck tumours. We investigated possible determinants of MP use in adolescent Australians using self-reported number of incoming and outgoing voice calls as exposure metric. RESULTS: There is a high prevalence of MP use amongst Australian adolescents (94%). Males were significantly younger than females at age of first uptake of MP (P= 0.02). Participants without siblings were significantly younger at age of first uptake. Personality traits were associated with regular MP usage: higher psychoticism scores were associated with regular use (IRR = 1.06, P= 0.03); there was a tendency for students with higher extraversion scores to report more MP use. Parental socio-economic status was associated with MP use, but parents who expressed moderate/high level concerns about possible health risks of use were more likely to have children who used MP (OR = 4.06, P= 0.05). CONCLUSIONS: Almost all adolescent Australians use MP, but regular exposure was associated with personality traits. Parental socio-economic status and perceived health risks of MP use were also associated with use of phones. Longitudinal studies are needed to assess the predictors of mobile phone use in the long term.

A new method to determine laterality of mobile telephone use in adolescents.

OBJECTIVES: As more children use mobile (cellular) telephones, public anxiety grows about the possible adverse health effects of radiofrequency (RF) exposure upon developing nervous systems. Most epidemiological studies investigating the health effects of mobile telephones have relied on self-reports from questionnaires. While there are some validation studies investigating the accuracy of self-reported mobile phone use in adults and adolescents, self-reported laterality of use has not been validated at any age. Although this study mainly sought to validate the accuracy of self-reported laterality of mobile telephone use in adolescents, investigation also covered number and duration of calls. METHODS: We monitored 455 calls in 30 students, mean age (SD) 14 (0.4) years. For 1 week, participants used hardware modified phones (HMPs) which logged dosimetric parameters such as laterality (side of head), date, number and duration of calls. These 'gold standard' measurements were compared with questionnaire self-reported laterality and estimated typical weekly phone use. RESULTS: Agreement between HMPs and self-reported laterality was modest (kappa=0.3, 95% CI 0.0 to 0.6). Concordance between HMP measured and self-reported number of calls was fair (intraclass correlation coefficient (ICC)=0.38, 95% CI 0.07 to 0.69), but poor for duration (ICC=0.01, 95% CI 0.00 to 0.37) with wide limits of agreement for both. CONCLUSIONS: These results suggest that adolescent self-reported laterality was of limited validity. Adolescent self-reported phone use by number and duration of calls was generally inaccurate but comparable to recent adult studies. Epidemiological studies of mobile phone use based on self-reported information may underestimate true associations with health effects.

How well do adolescents recall use of mobile telephones? Results of a validation study.

BACKGROUND: In the last decade mobile telephone use has become more widespread among children. Concerns expressed about possible health risks have led to epidemiological studies investigating adverse health outcomes associated with mobile telephone use. Most epidemiological studies have relied on self reported questionnaire responses to determine individual exposure. We sought to validate the accuracy of self reported adolescent mobile telephone use. METHODS: Participants were recruited from year 7 secondary school students in Melbourne, Australia. Adolescent recall of mobile telephone use was assessed using a self administered questionnaire which asked about number and average duration of calls per week. Validation of self reports was undertaken using Software Modified Phones (SMPs) which logged exposure details such as number and duration of calls. RESULTS: A total of 59 adolescents participated (39% boys, 61% girls). Overall a modest but significant rank correlation was found between self and validated number of voice calls (rho = 0.3, P = 0.04) with a sensitivity of 57% and specificity of 66%. Agreement between SMP measured and self reported duration of calls was poorer (rho = 0.1, P = 0.37). Participants whose parents belonged to the 4th socioeconomic stratum recalled mobile phone use better than others (rho = 0.6, P = 0.01). CONCLUSION: Adolescent recall of mobile telephone use was only modestly accurate. Caution is warranted in interpreting results of epidemiological studies investigating health effects of mobile phone use in this age group.

Comparison of measuring instruments for radiofrequency radiation from mobile telephones in epidemiological studies: implications for exposure assessment.

The debate on mobile telephone safety continues. Most epidemiological studies investigating health effects of radiofrequency (RF) radiation emitted by mobile phone handsets have been criticised for poor exposure assessment. Most of these studies relied on the historical reconstruction of participants' phone use by questionnaires. Such exposure assessment methods are prone to recall bias resulting in misclassification that may lead to conflicting conclusions. Although there have been some studies using software-modified phones (SMP) for exposure assessment in the literature, until now there is no published work on the use of hardware modified phones (HMPs) or RF dosimeters for studies of mobile phones and health outcomes. We reviewed existing literature on mobile phone epidemiology with particular attention to exposure assessment methods used. Owing to the inherent limitations of these assessment methods, we suggest that the use of HMPs may show promise for more accurate exposure assessment of RF radiation from mobile phones.

Personal, non-invasive dosimetry for radio-frequency human exposure assessment.

The integrity of data gathered by a body worn personal radiofrequency exposure meter has been investigated using computational methods. Simulations show that the distortion of the field by the body will cause measurement errors with a traditional 3-axis dipole field sensor. A modified measurement method for body worn personal exposure meters based on an array of 2-axis dipole field sensors is proposed. The approach minimizes the impact of body shielding (shadowing of the field) and could provide information on the average internal specific absorption rate (SAR) in various parts of the body.

Potential GPRS 900/180-MHz and WCDMA 1900-MHz interference to medical devices.

This study compared the potential for interference to medical devices from radio frequency (RF) fields radiated by GSM 900/1800-MHz, general packet radio service (GPRS) 900/1800-MHz, and wideband code division multiple access (WCDMA) 1900-MHz handsets. The study used a balanced half-wave dipole antenna, which was energized with a signal at the standard power level for each technology, and then brought towards the medical device while noting the distance at which interference became apparent. Additional testing was performed with signals that comply with the requirements of the international immunity standard to RF fields, IEC 61000-4-3. The testing provides a sense of the overall interference impact that GPRS and WCDMA (frequency division duplex) may have, relative to current mobile technologies, and to the internationally recognized standard for radiated RF immunity. Ten medical devices were tested: two pulse oximeters, a blood pressure monitor, a patient monitor, a humidifier, three models of cardiac defibrillator, and two models of infusion pump. Our conclusion from this and a related study on consumer devices is that WCDMA handsets are unlikely to be a significant interference threat to medical electronics at typical separation distances.

EEG electrode caps can reduce SAR induced in the head by GSM900 mobile phones.

This paper investigates the influence of EEG electrode caps on specific absorption rate (SAR) in the head from a GSM900 mobile phone (217-Hz modulation, peak power output 2 W). SAR measurements were recorded in an anthropomorphic phantom using a precision robotic system. Peak 10 g average SAR in the whole head and in just the temporal region was compared for three phantom arrangements; no cap, 64-electrode "Electro-Cap," and 64-electrode "Quick-Cap". Relative to the "no cap" arrangement, the Electro-Cap and Quick-Cap caused a peak SAR (10 g) reduction of 14% and 18% respectively in both the whole head and in the temporal region. Additional computational modeling confirmed that SAR (10 g) is reduced by the presence of electrode leads and that the extent of the effect varies according to the orientation of the leads with respect to the radiofrequency (RF) source. The modeling also indicated that the nonconductive shell between the electrodes and simulated head material does not significantly alter the electrode lead shielding effect. The observed SAR reductions are not likely to be sufficiently large to have accounted for null EEG findings in the past but should nonetheless be noted in studies aiming to measure and report human brain activity under similar exposure conditions.

Determining the influence of population variation on compliance with radiofrequency exposure limits: proposed study.

Currently, compliance with safety limits for human exposure to radiofrequency (RF) fields is demonstrated by methods that rely on certain assumptions and approximations, which include among other things, human anatomical features, tissue types and the dielectric properties of these tissues. This paper reviews some of the available data and outlines a proposal for an encompassing study to investigate which of these assumptions are appropriate; what approximation can be used in physical and computational modeling of humans for specific energy absorption rate (SAR) calculations (a key compliance metric); and what trade-offs can be made between accuracy and modeling requirements for practical considerations. Key issues to be investigated are how SAR varies between children and adults, between males and females, and how to model SAR in the fetus of pregnant females. It is hoped that the proposed study will produce models and methods which allow for faster, more accurate and more efficient compliance with radiofrequency exposure limits.