极低频电磁场生物效应的第二信使作用机制

随着人类社会的发展，日益增强的环境空间极低频电磁场已成为新的可能致癌源。揭示极低频电磁场生物效应的机制是防护其不良效应的关键。细胞内的第二信使在细胞外界作用因子的信号传递过程中起到承上启下的枢纽作用，因此研究第二信使有利于了解电磁场生物效应的机制。本文就极低频电磁场与细胞第二信使间的相互作用研究进展进行综述。     

孕期极低频电磁场暴露与出生缺陷关系

极低频电磁场(extremely low frequency electromagnetic fields,ELF-EMFs)是频率在300Hz以下的交变电磁场,主要由电力供应设备和各类家用电器产生.该频段的波长很长,本质上是一种感应场[1].国内外已经进行了大量极低频电磁场与人体健康的研究,发现极低频电磁场对神经系统、免疫系统、生殖系统等均可能产生影响,但是有关孕期ELF-EMFs与出生缺陷的研究还存在争议.本文从流行病学研究及动物实验2方面对孕期极低频电磁场暴露与出生缺陷的关系作一综述.     

工频电磁场暴露限值的确立依据及有关争议

工频电磁场（power frequency electromagnetic field）是由各种电压等级的输电线及用电器所产生的一种极低频电磁场,频率为50Hz或60Hz。为了防止其对人体产生的不良健康效应,一些国家和组织制订了工频电磁场的暴露标准。综述当前不同机构制定的有关工频电磁场的暴露限值,分析它们的制定依据及特点,同时也展示了围绕暴露限值方面的有关争议。     

极低频电磁场对大鼠脑组织抗氧化系统的影响

目的研究极低频电磁场对大鼠脑组织抗氧化系统的影响及其机制。方法选择健康成年Wistar大鼠20只,随机分为2组,即对照组和实验组,每组10只;实验组进行频率为12Hz、强度为0.9mT交变极低频电磁场暴露,每天暴露8h,连续15d,对照组不进行电磁场暴露。结果暴露于极低频电磁场的大鼠血清丙二醛(MDA)含量降低,脑组织中谷胱甘肽(GSH)含量和超氧化物歧化酶(SOD)活力明显增加,与对照组比较,差异有显著性(P<0.05或P<0.01)。结论频率为12Hz、强度为0.9mT的极低频电磁场可能具有增加抗氧化酶活力,使大鼠脑组织抗氧化能力增强的作用。     

工频磁场与有害理化因素联合暴露所致遗传损伤效应研究进展

工频磁场是指由高压输电线等供电设备以及大部分家用电器产生的频率为50或60 Hz的极低频磁场.自1979年Wertheimer和Leeper[1]报道了生活在高压输电线附近的儿童白血病发病率增高以来,工频磁场致癌效应的研究一直是生物电磁学领域的研究重点.2005年10月,世界卫生组织对极低频电磁场进行健康风险评估,认为尚无充分的流行病学证据和被认可的生物物理机制能够表明低强度工频磁场暴露与癌症发病有关[2].然而,在实际生活和职业环境中,工频磁场往往与一些有害理化因素联合暴露,这些联合暴露是否会诱发遗传损伤和癌症的发生已受到人们的关注.     

极低频电磁场与肿瘤关系研究进展

随着科技的进步和社会经济的迅速发展,各种电子、电力设备和设施的广泛应用使人们周围生活环境中的极低频电磁场强度日益增大,极低频电磁场与健康之间的关系引起了世界各国的关注,并开展了相应的研究.近些年来,对极低频电磁场与白血病、脑肿瘤、乳腺癌及其他肿瘤的发生的关系,国内外开展了大量的流行病学研究.该文综述了这些研究结果,并分析了极低频电磁场对肿瘤影响的可能作用机制.     

极低频电磁场孕期暴露对妊娠影响研究进展

极低频电磁场（extremely low frequency electromagnetic fields，ELF EMF）通常是指频率低于300Hz的电磁场。在日常的生产与生活环境中，ELF EMF主要来源于电力传输系统和各种电器设施，如高压输电线、家用电器等。随着电力的广泛应用，环境中ELF EMF的强度日益增高，在一定程度上已经威胁到人类的健康。近30年来，陆续有研究报道孕期暴露于ELF EMF可导致流产、宫内生长发育迟缓、     

电磁场暴露限值科学依据的探讨

国内在国际标准确定的极低频场暴露限值是否能保护公众健康的认识方面存在较大分歧。争议焦点集中在是否应针对未能证实的长期、低水平暴露的潜在健康风险制定限值,或是否应针对其＂健康效应＂制定＂预防性限值＂。而存在于上述争议背后的是围绕标准限值制定原则的一系列认识差异,包括：如何认识与理解电磁场的健康影响,依据什么准则来评价或解读单项研究的提示性结果,以及依据什么原则来制定公众卫生标准限值等。通过理解、分析世界卫生组织（WHO）关于制定暴露标准的指导原则;客观介绍国际、国内若干不同观点与论据;消化、分析WHO及其他国际组织针对极低频场健康风险的总体评估结论;结合中国国情及环境矛盾现状提出限值建议。中国作为诸多环境矛盾十分严峻的发展中国家,在涉及重大社会公共利益和高度敏感性的电磁场标准限值方面,应采纳以证据为基础的基本原则;在WHO＂向全人类提供相同或相似健康保护水平＂的目标指引下,在国际权威健康风险评估已完成的背景下,采纳国际标准是中国的合理选择;电磁场暴露标准限值应以防止＂已确定的健康危害＂为依据;不应以预防的名义制定任意的低暴露限值,从而破坏限值的科学基础;国内涉及极低频电场、磁场相关利益各方缺少沟通、对话与协商,是增加公众担忧以及强化公众风险感受的重要原因。采纳WHO推荐的国际标准是中国的合理选择,也是中国尽快摆脱电磁环境困扰的第一步。国家标准的尽早出台将为下一步通过各方协商,针对不确定的风险,制订适合中国国情的预防措施奠定基础。     

电磁场与人体健康

本文综述了超低频电磁场与人体健康的关系。一般认为暴露于电磁场对人体健康没有直接和明显的影响,但电磁场如具有生物学活性,且在其它条件存在的情况下,可能成为有害因素。现今社会人群广泛暴露于超低频电磁场,它们对人体健康的影响尚不清楚。流行病学研究中的方法学问题已成为危险度评定中的不肯定因素,因此,需更多的研究。     

极低频电磁场与细胞凋亡的研究进展

正随着电力的大力发展,特别是工业上某些高电压和强电流的广泛运用,使职业环境存在大量的极低频电磁场污染。近年来,已成为各国学者的研究热点[1-3]。电磁场生物效应产生的方式是通过电磁场改变生物组织(包括细胞、体液、自由基等)的特性[4]。极低频电磁场(extremely low frequency electromagnetic fields,ELF-EMF)指频率在100kHz以下的电磁场,主要存在于汽车制造业的     

ELF: exposure levels, bioeffects, and epidemiology

Considerable information has been obtained within the last decade describing biological effects, both real and potential, of extremely low frequency (ELF) electric and magnetic fields. Additionally, advances have also been made in defining the interactions between such fields and living systems. Many of the current studies concerning ELF electromagnetic fields are focused on understanding the mechanisms of interaction and in elucidating the issues of human health impact. This paper provides an overview of recent progress in ELF research including work on dosimetry of the fields, laboratory animal studies, cellular research, and epidemiology.     

A review of epidemiological studies of the health effects of living near or working with electricity generation and transmission equipment

In the last ten years there has been increasing concern that the extremely low frequency (ELF), non-ionising electromagnetic fields emitted by electrical installations and equipment using alternating current at 50-60 Hertz might have long-term effects on health. Studies of the association between disease and residence near installations transmitting or generating electricity and studies of the health of workers in the electrical industry are reviewed. Most of the investigations relate to cancer, although other conditions such as outcome of pregnancy have been studied. The most consistent finding is that electrical workers appear to be at increased risk of leukaemia, especially acute myeloid leukaemia. The effect is small. Combining the results of eleven separate investigations suggests an 18% increase in the risk of leukaemia (RR = 1.18, 95% confidence interval (CI) 1.09-1.29) which is partly or wholly due to a 46% increase in the risk of acute myeloid leukaemia (RR = 1.46, 95% CI 1.27-1.65). It is not clear whether this increase is specific to certain types of work within the electrical industry. Nor is it possible to determine from the available data if the increase in leukaemia is due to electromagnetic fields or to other factors to which electrical workers are exposed. There is no clear association between cancer risk and residence near sources transmitting electricity, although some data suggest that there may be small increases in leukaemia in those living very close to the sources. The relationship between adverse outcome of pregnancy and exposure to sources of ELF electromagnetic fields needs further investigation. Studies of the possible effects of ELF electromagnetic fields on health are hampered by problems in measuring exposure and by the ubiquity of exposure in the community.     

极低频电磁场生物学效应的细胞和分子生物学研究进展

综述关于极低频电磁场生物学效应的细胞和分子生物学研究结果，包括跨膜信号传递、酶活性、基因表达、细胞增殖、分化和凋亡以及基因突变和染色体畸变等方面。此外，就该领域的研究前号提出了几点看法。     

Exposure to extremely-low-frequency electromagnetic fields and radiofrequency radiation: cardiovascular effects in humans

Cardiovascular changes in humans exposed to nonionizing radiation [including extremely-low-frequency electromagnetic fields (ELF EMFs) and radiofrequency radiation (RFR)] are reviewed. Both acute and long-term effects have been investigated. In general, if heating does not occur during exposure, current flow appears to be necessary for major cardiovascular effects to ensue, such as those due to electric shock. Whereas most studies have revealed no acute effect of static or time-varying ELF EMFs on the blood pressure, heart rate, or electrocardiogram waveform, others have reported subtle effects on the heart rate. The possible health consequences of these results are unknown. Regarding long-term effects of ELF EMFs, reports from the former Soviet Union in the early 1960s indicated arrhythmias and tachycardia in high-voltage-switchyard workers. Subsequent studies in Western countries, however, did not confirm these findings. These studies are limited by uncertainties regarding exposure durations and appropriate control groups. Investigations of acute cardiovascular changes in humans purposely exposed to RFR have been limited to studies of magnetic resonance imaging (which, in addition to RFR, involves static and time-varying magnetic fields). It has been concluded that such exposures, as presently performed, are not likely to cause adverse cardiovascular effects. Reports of hypertension in workers potentially exposed to high levels of RFR during accidents are considered to be incidental (due to anxiety and posttraumatic stress). Soviet investigators have also indicated that long-term RFR exposure may result in hypotension and bradycardia or tachycardia. Other researchers, however, have been incapable of replicating these results, and some scientists have attributed the effects to chance variations and mishandling of data. In summary, studies have not yielded any obvious cardiovascular-related hazards of acute or long-term exposures to ELF EMFs or RFR at levels below current exposure standards. Received: 18 July 1996 / Accepted: 29 November 1996     

A literature review: the cardiovascular effects of exposure to extremely low frequency electromagnetic fields

The effects of exposure to extremely low frequency (ELF) electromagnetic fields (EMFs) on human cardiovascular parameters remain undetermined. Epidemiological studies have utilized dosimetry estimations of employee workplace exposure using altered heart rate variability (HRV) as predictive of certain cardiovascular pathologies. Laboratory studies have focused on macrocirculatory indicators including heart rate, HRV and blood pressure. Few studies have been conducted on the response of the microcirculatory system to EMF exposure. Attempts to replicate both epidemiological and laboratory studies have been mostly unsuccessful as study design, small sample populations and confounding variables have hampered progress to date. Identification of these problems, in the current context of international exposure guideline re-evaluation, is essential for future EMF studies. These studies should address the possible deleterious health effects of EMFs as well as the detection and characterization of subtle physiological changes they may induce. Recommendations for future work include investigating the macro- and microcirculatory relationship and the use of laboratory geomagnetic shielding.     

Interaction of extremely low frequency electric and magnetic fields with humans

The dosimetry and physical interaction mechanisms of electromagnetic fields with frequencies in the extremely low frequency (ELF) range (below 300 Hz) are described. The mechanisms through which ELF electric and magnetic fields induce electric currents in living organisms are summarized, with particular emphasis on humans. Topics that are discussed include: (1) sources and measurements of ELF electric and magnetic fields; (2) direct and indirect coupling of these fields to humans; (3) transient discharges and contact currents, and the thresholds for human response to these phenomena; (4) protective measures for the mitigation of potential ELF field effects on humans; and (5) mechanisms of interaction of ELF fields with cellular and tissue systems, with emphasis on field transduction mechanisms involving the cell membrane.     

极低频电磁场和射频电磁辐射对人体健康影响的研究进展

人们对电器设备的使用量日益增加造成生活环境电磁辐射污染,由此对人体的健康造成的影响和危害,越来越受到人们的关注.流行病学资料显示,不同频段、不同强度电磁辐射长期暴露可能对人体的健康造成影响.该文对极低频(ELF,3 Hz～3 kHz)电磁场和射频(RF,100kHz～300GHz)电磁辐射对人体健康影响包括神经系统、心...     

Effects of 100-μT extremely low frequency electromagnetic fields exposure on hematograms and blood chemistry in rats

The aim of this study was to test whether extremely low frequency electromagnetic fields (ELF EMFs) affect health or not. Here, we constructed a 100-μT/50 Hz electromagnetic field atmosphere. A total of 128 rats were randomly assigned into two groups: the ELF EMF group and the sham group. The ELF EMF group was exposed to 100-μT/50-Hz ELF EMF for 20 h per day for three months; at the same time the other group was exposed to a sham device without ELF EMF. During the three months, the weight was recorded every 2 weeks, and the water intake and food intake of the animals were recorded weekly. The hematologic parameters were detected before and after the exposure, whereas blood chemistry analysis was performed every 4 weeks. The general condition of the exposed rats was not affected by ELF EMF. Compared with the sham group, the hematograms were not significantly altered in the ELF EMF group. Similarly, the blood chemistry (including lipid profile, blood glucose, liver function and renal function of rats) from the ELF EMF group showed no difference compared with rats from the control group during the three months exposure. The present study indicated that short-term exposure of 100-μT/50-Hz ELF EMF may not affect hematograms and blood chemistry in rats.     

极低频电磁场对雄性成年大鼠生殖激素影响的实验研究

目的研究ELF EMFs对雄性生殖系统的毒性作用,系统观察ELF EMFs对暴露在不同参数及不同接触时间的雄性大鼠血清生殖激素的影响。方法健康雄性成年大鼠100只,随机分为对照组和实验组。将实验组大鼠按设计要求暴露在电磁场中,一定时间后,取对照组和实验组大鼠的血清,采用放射免疫分析(RIA)方法进行睾酮(T)、雌二醇(E_2)、卵泡刺激素(FSH)、黄体生成素(LH)等生殖激素进行检测。结果随着大鼠暴露ELF EMFs参数的加大,以及接触时间的延长,血清T、E2、FSH、LH浓度均呈现下降的趋势。结论ELF EMFs暴露对雄性大鼠血清T、E_2、FSH、LH等生殖激素的浓度具有影响,结果导致血清T、E_2、FSH、LH浓度呈现不同程度的下降,最终影响雄性大鼠的生殖能力。     

Intermittent extremely low frequency electromagnetic fields cause DNA damage in a dose-dependent way

Objectives Epidemiological studies have reported an association between exposure to extremely low frequency electromagnetic fields (ELF-EMFs) and increased risk of cancerous diseases, albeit without dose–effect relationships. The validity of such findings can be corroborated only by demonstration of dose-dependent DNA-damaging effects of ELF-EMFs in cells of human origin in vitro.Methods Cultured human diploid fibroblasts were exposed to intermittent ELF electromagnetic fields. DNA damage was determined by alkaline and neutral comet assay.Results ELF-EMF exposure (50 Hz, sinusoidal, 1–24 h, 20–1,000 T, 5 min on/10 min off) induced dose-dependent and time-dependent DNA single-strand and double-strand breaks. Effects occurred at a magnetic flux density as low as 35 T, being well below proposed International Commission of Non-Ionising Radiation Protection (ICNIRP) guidelines. After termination of exposure the induced comet tail factors returned to normal within 9 h.Conclusion The induced DNA damage is not based on thermal effects and arouses concern about environmental threshold limit values for ELF exposure.