極低頻電磁場量測

Abstract

早期的極低頻(30-3,000Hz) 研究範圍僅專注於50/60Hz架空,高壓交流輸 電線路所產生的電磁場.近年來,極低頻電磁場生物效應的研究已逐漸將焦 點轉移到住家(內)附近及工作場等電力頻率方面的磁場環境,而這些場源 的形態不同於可被特性化的架空電力線路,若以現有的ANSI/ IEEE(644-1979,1987)標準進行量測時,場的極化橢圓主軸方向不易判斷且 未必存在. 因此,本文建議量測儀表應具有窄頻慮波功能以區分同時存在 但不同頻率的場 強,並以合程場值作為量測場量以比較不同場源的場強. 由於部份流行病學研究結果所提 出的幾個毫高斯會對人體產生不利的生 物效應的假說並未獲得一致性結論且缺乏生物醫學 上的依據.因此,我們 建議以電氣生理學為依據的 IRPA/INIRC-1990暫定準則作為安全標準 的 參考. The early concerns regarding possible health effects due to field exposurewere fccused primarily on the extremely low frequency electric and magnetic fields near 50/60Hz AC overhead power lines.More recently,characterization of ambient power frequency magnetic fields in homes and in the workspace havealso received more attention. These magnetic field sources differ from the ge-ometry and current characteristics of overhead powerlines which can be defined fairy well. Because the existing ANSI/IEEE(644-1979,1987) standard is intende-d for characterizing power frequency magnetic fieldsnear power lines, it is fo-und not suitable for the measurement of residentialfields. This paper suggests that the instrumentation used in the fields measur-ements should have narrow-band filtering capability to distinguish the field intensities of different fr-equencies. In addition, in order to compare field strength of different magnet-ic field sources, resultant field strength shouldbe used. Although some epide-miological studies suggest that exposure to ELF magneticfields of several milli- gause may result in certain adverse health effects,butuntil now these presentation don't acquire accordant conclusions and lack of experimental evidences of biology and medicine to conform them. We, therefore, suggest that IRPA/INIRC-1990 interim guideline, based on electric physiology, may be followed when planniing on setting up limits of exposure to ELF electromagnetic fields.