各国工频电磁场的限值及其确定的依据

重点评述了一些国家以及国际组织标准中工频电磁场的限值及其确定的依据;介绍了目前普遍接受的低频电磁场模型。各国输电线路工频电磁场限值与暴露时长有关,不同地点限值的不同,对敏感区域额外增加预防性限值。目前工频电场限值较一致,磁场限值差异较大;ICNIRP导则已得到多国认可;对尚未确定长期的工频磁场暴露是否会导致特定种类的癌症及其它非癌症类疾病,需进一步研究以澄清电磁场作用于人体的微观机理。

Values and Rationales of Limits of Power Frequency Electric and Magnetic Fields in Various Countries

The effects of electric and magnetic fields on human body have attracted attention of the scientists and the public,especially when the EHV and UHV transmission lines are being constructed in China.This article is emphasized on the review of values and rationales of limit of power frequency electric and magnetic fields in standards and guidelines of various countries and international organizations.The general accepted induction models are introduced,with which t the current density in vivo caused by low frequency magnetic field as well as contact current caused by low frequency electric field can be simply calculated.Some characteristics of limit values of transmission lines are summarized.First,they depend on exposure time length,becoming larger when exposure time is shortened.Second,different values are designated for different areas.Those areas where the public frequently pass by are more strictly administrated.Third,additional precautionary limitations are provide for places of sensitive use,such as hospitals and schools.It can be deduced that the limit values of power frequency electric field in the literature are comparatively consistent,but on the contrary,great differences exist in limit values of power frequency magnetic field by reason of incompatible survey results between epidemiological studies and laboratory studies.The guideline of ICNIRP is admitted by quite a few countries as it is developed by a thorough review of all published scientific literature,which are evaluated according to critical criteria.Until now, no confirmative conclusions have been drawn about whether long-term exposure to power frequency magnetic field will induce certain types of cancers and some other non-cancer diseases,even if many investigations have been conducted and relative reports have been published on this subject.There is a lack of satisfactory mechanism of interaction of low frequency electric and magnetic fields with living system,so further researches are still needed.