Exposure Assessment to Radiofrequency Electromagnetic Fields in Occupational Military Scenarios: A Review

(1) Background: Radiofrequency radiations are used in most devices in current use and, consequently, the assessment of the human exposure to the radiofrequency radiations has become an issue of strong interest. Even if in the military field there is wide use of radiofrequency devices, a clear picture on the exposure assessment to the electromagnetic field of the human beings in the military scenario is still missing. (2) Methods: a review of the scientific literature regarding the assessment of the exposure of the military personnel to the RF specific to the military environment, was performed. (3) Results: the review has been performed grouping the scientific literature by the typology of military devices to which the military personnel can be exposed to. The military devices have been classified in four main classes, according to their intended use: communication devices, localization/surveillance devices, jammers and EM directed-energy weapons. (4) Discussion and Conclusions: The review showed that in the exposure conditions here evaluated, there were only occasional situations of overexposure, whereas in the majority of the conditions the exposure was below the worker exposure limits. Nevertheless, the limited number of studies and the lack of exposure assessment studies for some devices prevent us to draw definitive conclusions and encourage further studies on military exposure assessment.

Possible toxicity of chronic carbon dioxide exposure associated with mask use, particularly in pregnant women, children and adolescents – a scoping review

Literature was systematically reviewed regarding CO2 exposure and facemask use. Observational and experimental data are helpful for a risk-benefit assessment for masks as a popular non-pharmaceutical intervention against SARS-CoV2 in the populace. Masks impede breathing by increasing the resistance and dead space volume leading to a re-breathing of CO2 with every breath taken. Fresh air has around 0.04% CO2, while wearing masks more than 5 minutes bears a possible chronic exposure to carbon dioxide of 1.41–3.2% of the inhaled air. Although the buildup is usually within the short-term exposure limits, long-term consequences must be considered due to experimental data. US Navy toxicity experts set the exposure limits for submarines carrying female crews to 0.8% CO2 based on animal studies indicating an increased risk for stillbirths. Additionally, in mammals chronically exposed to 0.3% CO2 experimental data demonstrates teratogenicity with irreversible damage of neurons and reduced spatial learning caused by brainstem neuron apoptosis and a reduced blood level of the insulin-like growth factor 1. With significant impact on three readout parameters (morphological, functional, marker) this chronic 0.3% CO2 exposure has to be defined as being toxic. Additional data exists on the exposure of chronic 0.3% CO2 in adolescent mammals causing neuron destruction, which includes less activity, increased anxiety and impaired learning and memory. There is a possible negative impact risk by imposing extended mask mandates especially for vulnerable subgroups. Circumstantial evidence exists that extended mask use may be related to current observations of stillbirths and to reduced verbal motor and overall cognitive performance in children born during the pandemic. Extended masking in pregnant women, children and adolescents has not been thoroughly tested and studied. As a result of the animal experimental data available, a risk-benefit analysis is urgent and a need exists to rethink mask mandates, which provide appropriate warnings.

Magneto- and electrophosphene thresholds in the retina: a dosimetry modeling study

Objective: Sensations of flickering light produced by time-varying magnetic fields or electric currents are called magneto- or electrophosphenes. Phosphene thresholds have been used in international guidelines and standards as an estimate of the thresholds of exposure that produce effects in the central nervous system. However, the estimated threshold values have a large range of uncertainty. Approach: Phosphene thresholds were approximated by simulating five phosphene threshold experiments. Retinal electric fields and currents induced by electric and magnetic stimulation were calculated using the finite element method and 14 anatomically realistic computational models of human heads. Main results: The radial component of retinal current density was determined to be in the range of 6.0~--~20.6~mA/m$^2$. This study produces more accurate estimates for threshold current density in the retina using detailed anatomical models and the estimates had a reduced range of uncertainty compared to earlier studies. Significance: The results are useful for studying the mechanisms of retinal phosphenes and for the development of exposure limits for the central nervous system.

Characterisation of a Cold Atmospheric Pressure Plasma Torch for Medical Applications: Demonstration of Device Safety

The safety and effectiveness of plasma devices are of crucial importance for medical applications. This study presents the novel design of an atmospheric plasma torch (SteriPlas) and its characterisation. The SteriPlas was characterised to ascertain whether it is safe for application on human skin. The emission spectrum discharged from the SteriPlas was shown to be the same as the emission from the MicroPlaSter Beta. The UV emitted from the SteriPlas was measured, and the effective irradiance was calculated. The effective irradiance enabled the determination of the maximum UV exposure limits, which were shown to be over two hours: significantly longer than the current two-minute treatment time. The use of an extraction system with a higher flow rate appears to reduce slightly the effective irradiance at the treatment area. The NOx and ozone emissions were recorded for both SteriPlas configurations. The NOx levels were shown to be orders of magnitude lower than their safety limits. The ozone emissions were shown to be safe 25 mm from the SteriPlas cage. A discussion of how safety standards differ from one regulatory body to another is given.

Viability of cultured human skin cells treated with 1,6-hexamethylene diisocyanate monomer and its oligomer isocyanurate in different culture media

The isocyanate monomer 1,6-hexamethylene diisocyanate (HDI) and one of its trimers, HDI isocyanurate, are airway and skin sensitizers contained in polyurethane paint. The toxic response of cultured skin cells to these compounds was measured by evaluating the isocyanate concentrations at which 50% of the cells die (i.e., lethal concentration 50%, LC50) because the relative toxicity of each form of HDI should be considered when exposure limits of HDI-based paints are set. By using a luminescent ATP-viability assay, we compared the cytotoxic effects of HDI monomer and HDI isocyanurate on cultured human skin cells (keratinocytes, fibroblasts, and melanocytes) after 4-h isocyanate exposures using culture media with varying levels of nutrients in order to also determine the effects of media composition on isocyanate toxicity. Before analysis, experimental wells were normalized to controls containing cells that were cultured with the same vehicle and media. The measured mean LC50 values ranged from 5 to 200 µM across the experimental conditions, in which HDI isocyanurate in protein-devoid media was the most toxic to cells, producing the lowest LC50 values. For HDI monomer, keratinocytes were the most resistant to its toxicity and melanocytes were the most susceptible. However, when exposed to HDI isocyanurate, the opposite was observed, with melanocytes being the most resilient and the keratinocytes and fibroblasts were more susceptible. Depending on the type of skin cells, dose–response data indicated that HDI isocyanurate was 2–6 times more toxic than HDI monomer when using protein-devoid media whereas HDI isocyanurate was 4–13 times more toxic than HDI monomer when protein-rich media was used. Therefore, if the protein-devoid saline medium alone were used for these experiments, then a significant under-estimation of their relative toxicities in protein-rich environments would have resulted. This difference is because HDI monomer toxicity was more attenuated by the presence of protein in the culture media than HDI isocyanurate toxicity. Thus, conclusions based on comparative toxicity studies and consequent inference applied to potential human toxicity can be affected by in vitro culture media conditions. The physiochemical difference in reactivity of the two forms of HDI to biological molecules most likely explains the observed toxicity differences and may have implications for skin penetration, adverse effects like skin sensitization, and systemic responses like asthma. Future studies are warranted to investigate differences in the biological availability, cellular toxicity, and immunologic sensitization mechanisms for HDI monomer and HDI isocyanurate.

COMSOL modeling of the lightning-generated electric field distribution in a chain of insulators of a 115 kV power transmission line

The transmission lines installed in our city, to the outskirts of it and in the rest of the national territory produce a level of emissions of electric field, these levels vary depending on the physical disposition of the drivers, the distance between spans, the voltage level of the line, among others. These values must respect the exposure limits for individuals, as stipulated in Article 14 of RETIE. In this work will be developed a study of distribution of the electric field along a chain of insulators standard of tempered glass of a transmission line of 115 kV with the aid of the software COMSOL Multiphysics, to the impact of an atmospheric discharge on the storage cable with the help of ATPDraw software, taking into account variations in the value of the earthing resistance of the structure. With the electric field distribution values obtained by means of simulations carried out in the COMSOL Multiphysics software, comparisons are made of the magnitude of the obtained field, taking as a reference the stable state of the system without condition of pollutants. Initially a simulation of a transmission line of 115 kV is performed in the ATPDraw software, analyzing the lightning impulse generated on the guard cable, at different values of grounding resistance, to determine the waveform and reached value of overvoltage in the insulator chain. Then the overvoltage signal obtained with the help of ATPDraw software is recreated in the COMSOL Multiphysics software, to be able to visualize the distribution and behavior of the electric field along the chain, taking into account the different factors involved in the process, pollutants such as salinity, themes such as travelling waves etc. and thus determine possible line isolation failures by comparing the values achieved by simulating in COMSOL Multiphysics with respect to the CFO of the insulator chain.

Mathematical Modelling of Vertical Looped Water Slide Using Matlab

A conceptual mathematical model of a water slide with vertical loops is developed. The principle used is the conservation of energy. The thrill experienced by a rider on a water slide is mainly due to the variation of G-force acting on the rider through the course of the ride. The geometry of the slide is developed by plotting G-force variation with the arc length of the loop. The G-force exposure limits should meet with the standards set by the F24 committee on amusement parks and rides. The coordinates of the slide geometry are determined by using Euler’s method of discretized equations. Keywords: G-Force, Centripetal acceleration, Clothoid curve, Weightlessness, Potential Energy, Kinetic Energy

EMI radiation of power transmission lines in Malaysia

Background: There has been rising concern amongst the public regarding their home's proximity to high tension power transmission lines. The primary cause of fear is the impact of the electromagnetic interference (EMI) radiation on the nearby occupants' health. Despite the presence of national permissible limits of EMI radiation, there is still lack of information with regards to the EMI radiation of the types of power lines configuration in Malaysia. Methods: The electric and magnetic fields of several selected power transmission lines were simulated using the EMFACDC software program from the recommendation ITU-T K.90. Five types of power transmission lines available in Malaysia are considered. Results: It was found that the simulated electric and magnetic field levels at all the power lines' right of way (ROW) boundary complies with the prescribed exposure limit. However, the electromagnetic fields (EMF) level increases significantly as the separation distance is reduced from 30m. For a more conservative approach, the ROW can be set at 30m across all transmission voltage level and corridor area condition. Conclusion: It can be concluded that Malaysia's power transmission lines are within the prescribed exposure limits. To further minimize the electric and magnetic field level, it is recommended that the residential building should be built at least 30 meters away from the power transmission lines, especially for the 275kV double circuit, 275/132kV quadruple circuit, and 500kV double circuit lines.