Electric and magnetic fields (EMF): What do we know about the health effects?

Because we use electric power throughout our homes and workplaces, we are all subject to electric and magnetic fields (EMF) that are created by the voltages and currents present in electrical conductors and electrical equipment. Interest in the health effects of electric-power EMF has been motivated by several epidemiologic studies showing weak associations between surrogate measures of low-level EMF exposure and both childhood cancers and adult cancers. Due to the ubiquitous presence of electric power, the public health implications of this association are potentially very significant; however, good evidence for a causal relationship between exposure to EMF and any health effect has not been found. Yet, uncertainty, plus the suggestive epidemiologic findings, have fueled public anxiety and media attention. To put this potential health threat into perspective, it is important to consider the strength of the epidemiology, the availability of supporting animal studies, and mechanistic or biophysical information about the interaction of EMF with matter. Any discussion of steps that might be taken to avoid potential EMF health-effects needs to incorporate a perspective on how hypothetical EMF risks relate to other hazards to life and health.Work presented at the 23rd Congress on Occupational and Environmental Health in the Chemical Industry (Medichem 1995) The Chemical Industry as a Global Citizen - Balancing Risks and Benefits, 19-22 September 1995, Massachusetts Institute of Technology, Cambridge, Massachusetts     

极低频电磁场与儿童白血病关系的Meta分析

目的 探讨极低频电磁场与儿童白血病的关联程度.方法 采用Meta分析的方法,对国内外公开发表的8篇关于极低频电磁场与儿童白血病的流行病学研究文献进行综合定量再分析.根据资料一致性检验采用固定效应模型计算总OR值.结果 极低频电磁场与儿童白血病之间总OR值为1.58,95%可信区间（95%CI）为1.24～2.03,差异有统计学意义（χ^2=13.11,P＜0.01）.结论 极低频电磁场与儿童白血病具有高度联系,是儿童白血病的危险因素之一.     

妊娠期接受MRI磁场照射对子代大鼠不同发育期MAPK的影响

【目的】　研究妊娠期接受磁共振 (magneticresonanceimaging ,MRI)复合磁场照射对子代大鼠不同发育期脑部丝裂原活化蛋白激酶 (mitogenactivatedproteinkinase ,MAPK) /细胞外信号调节蛋白激酶 (extracellularsignalregulatedproteinkinase ,ERK )表达的影响。 　【方法】　SD孕鼠妊娠第 12～ 18d给予 0 .3 5TMRI磁场照射 ,雌性子鼠1、2、5月龄时进行大脑切片免疫组化SP方法染色 ,并用图像分析仪进行半定量分析。　【结果】　MAPK/ERK免疫反应在大鼠脑切片上广泛表达 ;随着年龄增长 ,未发现其表达的变化 ;在各年龄段子鼠照射组和对照组间MAPK/ERK的免疫反应表达差异均无显著性 (P >0 .0 5 )。　【结论】　妊娠期MRI磁场照射后并未引起子代大鼠MAPK/ERK免疫反应表达的异常     

电磁脉冲对兔眼晶状体辐射损伤的研究

目的探讨电磁脉冲(EMP)对兔眼晶状体的损伤作用.方法6×104V/m场强的EMP重复照射青紫蓝兔5次,于照后不同时间应用裂隙灯、光镜、激光扫描共聚焦显微镜和图像分析技术对兔眼晶状体辐射损伤进行检测.结果EMP辐射后30 d兔晶状体上皮细胞数目减少,胞核深染、固缩,AgNOR和DNA含量下降.照后90d晶状体上皮细胞增生,AgNOR和DNA含量升高,晶状体后囊水肿、空泡形成,白内障发生.结论高场强EMP辐射可导致晶状体损伤及白内障发生,辐射引起上皮细胞增殖异常是白内障发生的重要原因.     

移动电话射频电磁场对大鼠神经细胞微管结合蛋白2基因表达的影响

目的了解1．8 GHz移动电话射频电磁场(RF EMF)对大鼠神经细胞基因表达的影响,筛选射频电磁场反应基因。方法体外原代培养新生SD大鼠皮层和海马神经细胞至第13天,将细胞随机分为实验组(辐照组)和对照组(假辐照组)。实验组使用217 HZ调制的1．8 GHz射频电磁场,SAR为2 W/kg,间断辐照24 h(5 min开/10 min关)；对照组置于同样的波导腔中,但不输入射频信号,进行假辐照。辐照后即刻抽提两组细胞的总RNA,然后用Rat Neurobiology U34 array基因芯片进行基因转录水平分析,找到可能的RF EMF反应候选基因。利用核糖核酸酶保护分析(RPA)法对功能相对明确、表达丰度和表达相对比值较高的变化基因进行验证。结果在Rat Neurobiology U34 array 1 200个候选基因中,筛选出34个差异表达基因,从中确定上调基因微管结合蛋白2(microtubule associated protein 2,Map2)为候选基因,经RPA方法验证,差异有统计学意义(P＜0．05)。结论Map2作为神经细胞特有的骨架蛋白,它的表达和功能的调控对于神经细胞维持正常细胞骨架和功能十分重要。1．8 GHz射频辐照可以引起大鼠神经细胞Map2基因表达上调。     

电磁场促进骨折愈合的研究进展

目的:探讨电磁场促进骨折愈合的研究进展。方法:阅读、研究国内外有关文献并进行综述。结果与结论:从实验研究、临床应用及作用机理3方面证实电磁场对骨折愈合有促进作用。     

军队老年人阿尔茨海默病危险因素的病例对照研究

目的 探讨军队老年人阿尔茨海默病(AD)的危险因素,初步分析早年电磁暴露与AD的关系。方法 采用病例对照研究。选择解放军总医院近年来确诊的62例军队AD患者为病例组,在同一医院住院治疗的离退休老干部中按照年龄段分层抽样(按1:2比例)选取124例对照。调查方式为电话访谈。结果 单因素分析结果显示,病例组社会活动情况明显少于对照组,早年电磁暴露、体育锻炼情况、负性生活事件、慢性阻塞性肺病病史、既往癌症病史、痴呆家族史在两组间差异有显著性。在调整相关影响因素后,负性生活事件、痴呆家族史、社会活动量的OR值(95％CI)分别为3.27(1.53～6.97)、5.78(1.39～24.10)和0.81(0.72～0.92),早年电磁暴露的OR值(95％CI)为2.49(0.96～6.45),而既往癌症病史和吸烟似与AD呈负相关。结论 负性生活事件、痴呆家族史、社会活动减少是AD的独立危险因素,早年电磁暴露是其可能的危险因素;吸烟和既往癌症病史与AD呈负相关的原因可能与该老年人群的“生存偏性”有关。     

A low‐cost,mechanically simple apparatus for measuring eddy current‐induced magnetic fields in MRI

The fidelity of gradient waveforms in MRI pulse sequences is essential to the acquisition of images and spectra with minimal distortion artefacts. Gradient waveforms can become nonideal when eddy currents are created in nearby conducting structures; however, the resultant magnetic fields can be characterised and compensated for by measuring the spatial and temporal field response following a gradient impulse. This can be accomplished using a grid of radiofrequency (RF) coils. The RF coils must adhere to strict performance requirements: they must achieve a high sensitivity and signal‐to‐noise ratio (SNR), have minimal susceptibility field gradients between the sample and surrounding material interfaces and be highly decoupled from each other. In this study, an apparatus is presented that accomplishes these tasks with a low‐cost, mechanically simple solution. The coil system consists of six transmit/receive RF coils immersed in a high‐molarity saline solution. The sensitivity and SNR following an excitation pulse are sufficiently high to allow accurate phase measurements during free‐induction decays; the intrinsic susceptibility matching of the materials, because of the unique design of the coil system, results in sufficiently narrow spectral line widths (mean of 19 Hz), and adjacent RF coils are highly decoupled (mean S₁₂ of ?47 dB). The temporal and spatial distributions of eddy currents following a gradient pulse are measured to validate the efficacy of the design, and the resultant amplitudes and time constants required for zeroth‐ and first‐order compensation are provided. Copyright © 2013 John Wiley & Sons, Ltd.     

Supplementary values of the dosimetric parameters kNR and Em for various types of detectors in 6 and 15 MV photon fields

The present communication broadens the data base for determinations of the non-reference condition correction factor k_NR needed in high-energy photon dosimetry to accomplish the use of various detectors under non-reference conditions. Following our previous strategy of calculating semiempirical values of k_NR and correlating them with the mean photon energy E_m at the point of measurement in a large water phantom, the values of E_m are now stated for 6 and 15 MV photon radiations of accelerators with and without flattening filters, square field sizes from 1 to 30 cm side length and depths from 0 to 28 cm. The unambiguity of the k_NR-E_m correlation is again confirmed and is quantified by fitting formulae for air-filled ionization chambers, TLD detectors and Si diodes. This survey provides a practicable access to the k_NR values, particularly for the non-water equivalent detectors to be used in small-field dosimetry     

Elliptical localization with pulsed second‐order fields (ECLIPSE) for robust lipid suppression in proton MRSI

Proton MRSI has great clinical potential for metabolic mapping of the healthy and pathological human brain. Unfortunately, the promise has not yet been fully achieved due to numerous technical challenges related to insufficient spectral quality caused by magnetic field inhomogeneity, insufficient RF transmit power and incomplete lipid suppression. Here a robust, novel method for lipid suppression in ¹H MRSI is presented. The method is based on 2D spatial localization of an elliptical region of interest using pulsed second‐order spherical harmonic (SH) magnetic fields. A dedicated, high‐amplitude second‐order SH gradient setup was designed and constructed, containing coils to generate Z2, X2Y2 and XY magnetic fields. Simulations and phantom MRI results are used to demonstrate the principles of the method and illustrate the manifestation of chemical shift displacement. ¹H MRSI on human brain in vivo demonstrates high quality, robust suppression of extracranial lipids. The method allows a wide range of inner or outer volume selection or suppression and should find application in MRSI, reduced‐field‐of‐view MRI and single‐volume MRS.