Dosimetry of electromagnetic field exposure of an active armlet and its electromagnetic interference to the cardiac pacemakers using adult,child and infant models

ABSTRACT

Wearable devices have been popularly used with people from different age groups. As a consequence, the concerns of their electromagnetic field (EMF) exposure to the human body and their electromagnetic interference (EMI) to the implanted medical devices have attracted many studies. The aim of this study was to evaluate the human exposure to the EMF of an active radiofrequency identification (RFID) armlet as well as its EMI to the cardiac pacemaker (CP). Different human models from various age groups were applied to assess the result variability. The scalar potential finite element method was utilized in the simulation. Local EMF exposure and the exposure to the central nerve system tissues were evaluated using different metrics. EMI to the CP was assessed in terms of the conducted voltage to the CP. The results from all the models revealed that the studied RFID armlet would not produce the EMF exposure exceeding the safety limits. The calculated interference voltage was highly dependent on the distance between the RFID armlet and the CP (i.e. the physical dimension of the individual model). The results proposed to evaluate the appropriateness of the current EMI measurement protocol for this kind of devices used by the infants.     

A quantitative evaluation of ten approaches to setting site‐specific cleanup objectives

Over the past several years, a number of reviews of various approaches employed or proposed by different jurisdictions for setting contaminated site cleanup objectives have been conducted. These methods are normally divided into two groups: absolute and relative. The absolute approach establishes a numerical concentration for a contaminant in soil that is applied to all sites, regardless of site‐specific factors. The relative approach generally employs a risk assessment modeling technique to derive a soil cleanup number based on site‐specific and chemical‐specific factors that will result in an acceptable exposure or risk. In the latter case, the numerical concentrations may vary from site to site, but the risk is the same. In the former, the numerical concentration is the same from site to site, but the risk, although unstated, varies. Numerous reviews of these methods have been undertaken, but all have been qualitative in nature, examining theoretical bases and not comparing the actual performance of each method in the assessment of one site. We have undertaken to derive cleanup guidelines for a single, existing contaminated site in Canada using ten different methods. Five of these were absolute methods (British Columbia Assessment Criteria, Alberta Soil Guidelines, Ontario Decommissioning Guidelines, Quebec ABC's, and New Jersey Acceptable Soil Contaminant Levels) and five were relative methods (U.S. Environmental Protection Agency Public Health Evaluation Manual, U.S. Army Primary Pollutant Limit Values, California Site Mitigation Decision Tree, California Technical Standard, and AERIS). The resulting analysis compares relative methods to absolute, examines the strengths and weaknesses of each approach, and discusses the similarities and differences of the outputs of the various approaches when employed to set cleanup objectives.     

Human perception of electric fields and ion currents associated with high-voltage DC transmission lines

The objective of this study was to assess the ability of humans to detect the presence of DC electric fields and ion currents. An exposure chamber simulating conditions present in the vicinity of high-voltage DC (HVDC) lines was designed and built for this purpose. In these experiments, the facility was used to expose observers to DC electric fields up to 50 kV/m and ion current densities up to 120 nA/m². Forty-eight volunteers (25 women and 23 men) between the ages of 18 and 57 years served as observers. Perception of DC fields was examined by using two psychophysical methods: an adaptive staircase procedure and a rating method derived from signal-detection theory. Subjects completed three different series of observations by using each of these methods: one was conducted without ion currents, and the other two involved various combinations of electric fields and ion currents. Overall, subjects were significantly more likely to detect DC fields as the intensity increased. Observers were able to detect the presence of DC fields alone, but only at high intensities; the average threshold was 45 kV/m. Except in the most sensitive individuals, ion current densities up to 60 nA/m² did not significantly facilitate the detection of DC fields. However, higher ion current densities were associated with a substantial lowering of sensory thresholds in a large majority of observers. Data analysis also revealed large variations in perceptual thresholds among observers. Normative data indicating DC field and ion current intensities that can be detected by 50% of all observers are provided. In addition, for the most sensitive observers, several other detection proportions were derived from the distribution of individual detection capabilities. These data can form the basis for environmental guidelines relating to the design of HVDC lines. © 1996 Wiley-Liss, Inc.     

脉冲电磁波对球形大脑作用的理论计算

建立了脑球体模型,赋于脑壳与内部组织不同的电参数,应用时域有限差分法（ＦＤＴＤ）计算了在脉冲电磁波辐射下脑内各点电场的瞬时波形及相应的比吸收率ＳＡＲ。计算结果表明,脉冲电磁波对大脑的瞬态作用时间比脉冲宽度要长,且各点波形不尽相同,但在脑中心有最大的ＳＡＲ,对此讨论了其安全性     

人体电磁兼容系统与电磁场处理水--Ⅲ.电磁水对人体电磁场的作用

《人体电磁兼容系统与电磁场处理水》一文分三篇写。第一篇“Ⅰ.人体电磁兼容系统”,讨论了人体体内电磁场;第二篇“Ⅱ·电磁水的特性”,讨论了电磁水的电磁场。二文均已发表于《生物磁学》。本文是第三篇,讨论电磁水电磁场对人体电磁场的作用,重点阐明饮用电磁水后,主要是电磁水的电磁场作为入射场与体内场发生迭加作用,产生耦合电磁场,从而实现其对体内场的调节作用,达到维系身体健康的目的。由于有关水的问题非常复杂,动态性强,故大多数关于耦合场的研究均服从于“统计学规律”。     

Soil Cleanup Goal for Dioxin Using Probabilistic Risk Assessment Techniques

State regulators in Florida recently approved a first-of-its-kind probabilistic risk assessment (PRA) for determining an alternative residential Soil Cleanup Target Level (SCTL) for dioxin (32 ng/kg TEQ). The default residential SCTL (7 ng/kg TEQ) is based on a single, deterministic calculation with numerous conservative assumptions, resulting in an overly conservative value far beyond the regulatory mandate (i.e., 10^?6 increase in cancer risk). Conversely, this PRA used a Monte Carlo simulation to estimate risk for all members of a large population using a combination of scientific data and professional judgment, with final details developed during negotiations with regulators. The simulation parameters were defined probabilistically and reflect the ranges of values for the following exposure variables: body weight, exposure duration, exposure frequency, fraction from contaminated source, soil ingestion rate, and relative bioavailability. Other variable and uncertain parameters were treated deterministically per direction from the regulators. The state also required that a pre-supposed high-risk subpopulation be analyzed separate from the full receptor population. Despite the conservativeness of the alternative SCTL, this PRA represents a significant step toward more realistic estimates of human health risks caused by environmental contaminant exposure.     

Dysregulation of Autonomic Control of Cardiac Function in Workers at am Broadcasting Stations (0.738–1.503 MHz)

Ninety-three adult males working at AM broadcasting stations (0.738–1.503 MHz) or radio line stations volunteered for cardiological examinations. The examinations included routine electrocardiogram (ECG) at rest, analysis of heart rate variability (HRV), Holter 24-h ECG, and 24-h ambulatory blood pressure (ABP). Results of cardiological examinations were correlated with individual exposure to EM fields (maximum exposure levels during working shift, daily exposure dose, and cumulative lifetime exposure). Of the 93 subjects qualified for the study, 71 (76.3%) experienced occupational RF exposure, while the remaining 22 (23.7%) had no history of regular EM exposure. ECG abnormalities or pathological changes were recorded quite frequently (50–70%) in both exposed and control populations. There was no correlation with exposure levels. We found measurable effects in the HRV and ABP parameters in the EM-exposed population, but none could be assigned clinical significance. The results suggest that exposure of workers to EM fields can cause slight disturbances in autonomic cardiac regulation and slight dysregulation of circadian rhythms in workers exposed to EM fields exceeding 100–150 V/m.     

Effects of high-frequency electromagnetic fields on human lymphocytes in vitro

Human peripheral lymphocytes were incubated in the presence of high-frequency electromagnetic fields of 380, 900 and 1800 MHz. The measured endpoints were cell cycle progression and the frequencies of sister-chromatid exchanges. No differences between treated and control cultures could be found.     

RF Exposure During Use of Electrosurgical Units

Electrosurgical units (ESUs) commonly used in operating suites employ radiofrequency (RF) energy for cutting and coagulation, and operate at different frequencies in the range 0.3–5 MHz. Around the electrode and cables, electric and magnetic fields at similar frequencies will be generated, and the surgeon using the ESU will therefore be exposed to these electromagnetic fields. In this study we have measured the levels of RF fields near the lead wires of two electrosurgical units, BARD 3000 operating at a fixed frequency of 0.5 MHz, and ERBE ICC 350 with a frequency range from 0.3 to 1 MHz. Electric fields were measured at distances from 5–30 cm from the lead wire. Measurements were done with the ESU both cutting and coagulating, and power levels ranging from 10–100 W. The magnetic field outside the lead wire was calculated from the measured current through the leads using standard theory. Using those measurements as a base, the calculated local exposure of the surgeon's hand was estimated to exceed 15 kV/m for the electric field and the corresponding value for the magnetic field was 16 µT. These calculations exceed the suggested international reference levels at 0.5 MHz (610 V/m and 4 µT, respectively).     

Extremely low-frequency electromagnetic fields affect lipid-linked Carbonic anhydrase

In the last years, the effect of extremely low-frequency electromagnetic fields (ELF-EMF) on the activity of different enzymes were investigated. Only the membrane-anchored enzymes did decrease their activity, up to 50%. In this work, the effect of ELF-EMF on bovine lung membrane carbonic anhydrase (CA) were studied. Carbonic anhydrases are a family of 14 zinc-containing isozymes catalyzing the reversible reaction: CO₂+H₂O = HCO₃^? +H⁺. CA differ in catalytic activity and subcellular localization. CA IV, IX, XII, XIV, and XV are membrane bound. In particular, CA IV, which is expressed in the lung, is glycosyl phosphatidyl inositol-linked to the membrane, therefore it was a candidate to inhibition by ELF-EMF. Exposure to the membranes to a field of 75 Hz frequency and different amplitudes caused CA activity to a reproducible decrease in enzymatic activity by 17% with a threshold of about 0.74 mT. The decrease in enzymatic activity was independent of the time of permanence in the field and was completely reversible. When the source of enzyme was solubilized with Triton, the field lost its effect on CA enzymatic activity, suggesting a crucial role of the membrane, as well as of the particular linkage of the enzyme to it, in determining the conditions for CA inactivation. Results are discussed in terms of the possible physiologic effects of CA inhibition in target organs.