環境建議值(參照水平)由基本限制值導出
陳椒華/20120327
2001年行政院環保署公告環境建議值，乃是根據「國際非游離輻射防護委員」會(ICNIRP)導則制定，2010年ICNIRP修正導則。本文根據ICNIRP所修正導則，提出環保署公告的環境建議值(參照水平，reference level)，乃是由基本限制值(Basic restriction)導出，而基本限制值為瞬間或短時間暴露值，故環境建議值(參照水平)不是長時間暴露限制值，不是長時間暴露安全值。
一、ICNIRP出版限制電場、磁場（EMF）曝露導則
2010年 ICNIRP修正出版電場、磁場（EMF）導則，替代1998年版之低頻部分(1Hz~100KHz)。 ICNIRP出版EMF導則的主要目的是建立限制電場、磁場（EMF）曝露的導則，它將為防止所有已確定的(註1)有害健康的影響提供保護。已經對EMF 直接和間接影響的研究進行了評估：直接影響是源於場與人體的直接作用；非直接影響包括與導電物體（該物體所具有的電位與人體不同）的相互作用。導則的限值是基於已確定的關於急性效應的證據；現有的可用的知識指出，遵循這些限值可保護職工和公眾免受低頻電磁場曝露的有害健康影響。
二、在更高的暴露水平，通常只允許更短的暴露時間
根據 WHO 2006年出版「 Framework for Developing health-based electromagnetic fields standards」(制定以健康為基礎的EMF標準的框架)，在”4.5 暴露標準制定的要求”(p25)，提出為確保暴露標準所有要素的完整，以下幾點必須注意:
1.「暴露水平」: 在實際應用中，可以用「參照水平」來表示「暴露水平」。多個頻率場同時暴露的情況必須在標準中有所說明。
2.「暴露持續時間」:不同能量水平的暴露時間應該是十分確切的。在很多標準中，確定的能量水平是針對8-24小時/天的暴露時間，但在更高的暴露水平，通常只允許更短的暴露時間，在這方面，暴露水平的時間平均是很重要的。應明確地指出平均暴露的含義，以使有責任執行標準的人不產生理解的混淆。
三、暴露限值是基於短期急性暴露而不是長期暴露的影響
根據WHO 2002年「ESTABLISHING A DIALOGUEON RISKS FROM ELECTROMAGNETIC FIELDS」第3章指出: 暴露限值是基於短期急性暴露而不是長期暴露的影響，因為有關電磁場長期、低水平暴露的可用科學信息被認為不足以制定量化限值。
文中也指出”ICNIRP使用了10倍的降低因子而得出職業暴露限值，使用了50倍的降低因子而得出公眾暴露限值，限值隨頻率不同而變化，因此低頻場(如電力線路)和高頻場(如移動電話)的限值不同。
文中也指出職業暴露人群由已經普遍認識到電磁場及其影響的成年工作人員組成。這些工作人員經過培訓，知道潛在的風險和應採取的適當防範措施。相較之下，普通公眾中包含了年齡層次和健康狀況各樣的人，在很多情況下，他們不知道自己暴露在電磁場中。另外，工作人員一般僅在工作日才受到暴露(通常每天8小時)，而普通公眾的暴露時間則可能達到每天24小時)。(註2)
四、「降低因子」(Reduction factor)的目的是降低影響閾值以補償導則制定過程中各種不確定源的影響。
根據2002年及2010年ICNIRP導則及資料，「降低因子」(Reduction factor)的目的是降低影響閾值以補償導則制定過程中各種不確定源的影響。而一些曝露影響閾值水平不確定源的例子包括：將動物影響數據外推到對人的影響；不同人由於耐受性差異造成的生理學儲備的差異和劑量-反應關系統計上的不確定性（置信區間）。當曝露和不良後果之間的關係的正確與確定是較低的，較大的降低可能有必要。
事實上，「降低因子」並非專指長期(8小時,24小時)暴露才需要的降低因子。有的官方資料(環保署)一再強調「降低因子」是因為長期(8小時,24小時)暴露才運用，顯然不正確 (註3)，事實上，「降低因子」是為補償導則制定過程中各種不確定源的影響。
五、參照水平由基本限制值導出
參照水平是通過數學模型、使用已發布的數據，由基本限值獲得
（Dimbylow2005，2006）。它們是按照場對人體曝露最大耦合條件計算得到的，因而可提供最大保護。考慮了頻率相關性和劑量不確定性。參照水平考慮了兩種不同的效應和腦中感應電場的近似綜合性。既有與中樞神經系統效應（以及在體內非中樞神經系統組織內的感應電場）的關系，又有與周圍神經系統的關系
（即：在50Hz，用於把對中樞神經系統影響的基本限值轉換到外磁場曝露的系數為每T 相當於 33 V m-1，而對周圍神經系統影響的系數為每T 相當於60 V m-1。考慮劑量的不確定性，對這些計算值賦予了3 倍的附加降低因子）。(2010 ICNIRP p826,827, 中文翻譯 p22,23)
25 Hz 及以下職業曝露的電場參照水平包含了足夠的安全裕度來預防所有可能情況下的接觸電流刺激效應。；在25 Hz 和10 MHz 範圍內，參照水平根據感應電場的基本限值制定，這樣，在該頻段內就有可能沒有提供足夠的安全裕度來防止所有可能條件下接觸電流的刺激效應；對10 MHz 及以下的公眾曝露電場參照水平可使90%以上的受曝露個體免受有害的非直接影響（電擊和灼痛）。另外，50 Hz 及以下公眾曝露參照水平包含足夠的裕度避免表面電荷效應（比如大多數人的感覺）。(2010 ICNIRP p827, 中文翻譯 p23)
隨場的方向和人體模型不同，由每 mT 50Hz 磁場在腦中感應的最高局部峰值電場的值約為23~33 mV m-1。對周圍神經組織，目前還沒有可用的轉換系數，因而選擇包含周圍神經末梢的皮膚作為最壞情況下的目標組織。由每 mT上述場在皮膚感應的電場約為20~60 mV m-1。 每kV m-1 的50Hz 電場在腦中引起的最大局部電場約為.7~2.6mV m-1。而每kV m-1 的50Hz 電場在皮膚引起的最大局部電場約為12~33 mV m-1。(2010 ICNIRP p827, 中文翻譯 p17)
六、基本限制值為短時間暴露限值
2010年ICNIRP導則出版的主要目的是建立防止有害健康影響的限制電磁場曝露的導則。如上所述，風險來自短暫的神經系統響應，包括對周圍神經（PNS）和中央神經（CNS）的刺激、視網膜光幻視和對腦功能一些方面的可能影響。有關「時間平均」，對包括暫態或非常短期峰值的電場或磁場，ICNIRP 推薦的體內電場限值應看作瞬時值而不應是時間平均值 。(2010 ICNIRP p825, 中文翻譯p20)
註1: 所謂已確定的機制 (Established mechanism)具有以下特性的生物電機制：(2010 ICNIRP p833)（a）能用於預測人體的生物效應；（b）通過方程或參數關系可以建立具體的模型；（c）已經在人體中得到證實或者動物數據能可信地外推到人體上；（d）有強證據支持；（e）被科學界專家廣泛接受。
註2: 考量公眾可能暴露長達24小時，並非指暴露限值是24小時的「長期暴露限值」
註3:環保署涉誤導降低因子(折減係數)為長期暴露而設:
環保署資料指:「 …為了顧慮暴露之健康風險，分別對一般民眾暴露限值(即每日24小時暴露) 已納入50倍的折減係數考量；職業人員暴露限值(即每日少於8小時之暴露) 已納入10倍的折減係數考量”」
表一、基本限制值與參照水平(環境建議值) 關係(1)
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| 內部電場閾值(基本限制值) | 外部電場閾值 (參考水平) | 磁通密度B(T) 每T=10000000mG |
| 職業暴露 | 體內基本現值頭部中央神經 | 100mVm-1 (50Hz)
50mVm-1 (10Hz~25Hz) | 10 kV m-1 (50Hz)
20 kV m-1 (10Hz~25Hz) | 100m Vm-1 =(100/33) x10-3 T)= (3x10-3 T)(在50Hz，用於把對中樞神經系統影響的基本限值轉換到外磁場曝露的系數為每T 相當於 33 V m-1) 3 倍的附加降低因子 1 x10-3T =10000mG(50Hz)
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| 頭部和軀體所有組織 | 800 mV m-1 |
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| 公眾暴露 | 體內基本現值頭部中央神經 | 20 mV m-1 (50Hz)
10mVm-1 (10Hz~25Hz) | 5 kVm-1 (50Hz)
5 kVm-1 (10Hz~25Hz) | 20x10-3 /33= 6 x10-4 T 3 倍的附加降低因子 2 x10-4 T =2000mG(50Hz)
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| 頭部和軀體所有組織 | 400 mV m-1(50Hz) |
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（在50Hz，用於把對中樞神經系統影響的基本限值轉換到外磁場曝露的系數為每T 相當於 33 V m-1）
表二、基本限制值與參照水平(環境建議值) 關係(2)
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| 內部電場閾值(基本限制值) | 外部電場閾值 (參考水平) | 磁通密度B(T) (參考水平) 每T=10000000mG | 外部電場閾值 | 內部電場閾值 |
| 職業暴露 | 體內基本現值 頭部中央神經 | 2x10-3 f (V m-1) 0.1 V m-1 =100mVm-1 (50Hz)
50mVm-1 (10Hz~25Hz) |
10 kV m-1 (50Hz)
20 kV m-1 (10Hz~25Hz)
| 100m Vm-1 =3 x10-3 T
3 倍的附加降低因子
1 x10-3T =10000mG (50Hz) （即：在50Hz，用於把對中樞神經系統影響的基本限值轉換到外磁場曝露的系數為每T 相當於 33 V m-1 | 對50~60Hz，最敏感的10%志願者的直接感覺閾值在2-5 kV m-1； 而5%志願者在15-20 kV m-1 時感覺煩惱。在5 kV m-1 時7%的志願者在電氣觸地時感到痛感，而有50%在 10 kV m-1 電場中碰觸地時感到痛感。(2010ICNIRP p6) | 對頻率範圍從10Hz 到25Hz，職業曝露應限制頭部中央神經系統組織（即腦和視網膜）中感應電場強度不超過 50 mVm-1以避免視網膜光幻視。該限值也應能防止任何對腦功能可能的暫時影響 (2010 ICNIRP p19) |
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| 頭部和軀體所有組織 | 800 m V m-1 |
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| 根據使用神經模型的理論計算，人體周圍神經系統(PNS）有髓神經纖維最小的閾值大約為6 V m-1（峰值）…；估計周圍神經刺激的最小閾值在4-6 V m-1（取決於設定刺激發生在皮膚或皮下脂肪）(p7) |
| 公眾暴露 | 體內基本現值 頭部中央神經 | 4x10-4 f(V m-1) 0.02 V m-1 =20 mV m-1 (50Hz)
10mVm-1 (10Hz~25Hz) | 5 kVm-1 (50Hz)
5 kVm-1 (10Hz~25Hz)
| 20x x10-3 /33= 6 x10-4 T
3 倍的附加降低因子 2 x10-4 T =2000mG(50Hz) （即：在50Hz，用於把對中樞神經系統影響的基本限值轉換到外磁場曝露的系數為每T 相當於 33 V m-1 |
| 對公眾而言，針對頭部的中央神經組織應用了 5 倍的降低因子，得出曝露基本限值在10 到25Hz 為10 mV m-1。高於或低於上述頻率，基本限值提高(2010ICNIRP p19) |
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| 頭部和軀體所有組織 | 400 mV m-1 ((10Hz~25Hz , 50Hz) |
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（即：在50Hz，用於把對中樞神經系統影響的基本限值轉換到外磁場曝露的系數為每T 相當於 33 V m-1，
(以上資料來源見下表整理)
| (2010 ICNIRP p819) In view of the uncertainty inherent in the scientific data, reduction factors have been applied in establishing the exposure guidelines. For details see ICNIRP 2002. |
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| Reduction factor (2010 ICNIRP p836)
Reduction of the effect threshold to compensate for various sources of uncertainty in the guideline setting process. Some examples of sources of uncertainty about exposure-effect threshold levels include the extrapolation of animal data to effects on humans, differences in the physiological reserves of different people with corresponding differences in tolerance, and statistical uncertainties (confidence limits) in the dose-response function. In ICNIRP’s view, uncertainty in measurements used to implement the guidelines is a problem more appropriate to the functions of organizations responsible for the development of compliance methods. It is not considered in the setting of reduction factors by ICNIRP. | 降低因子 Reduction factor
降低影響閾值以補償導則制定過程中各種不確定源的影響。 一些曝露影響閾值水平不確定源的例子包括：
將動物影響數據外推到對人的影響；不同人由於耐受性差異造成的生理學儲備的差異和劑量-反應關系統計上的不確定性（置信區間）。在ICNIRP 看來，應用導則時的測量不確定性對負責提出相符性方法的機構而言是更現實的問題。ICNIRP 在設定降低因子中沒有考慮這一點。
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| The use of reduction factors (2002 ICNIRP p546) The identification and quantification of various adverse effects of NIR exposure on health and wellbeing are difficult at best, and such judgements require extensive experience and expertise. Uncertainties in the knowledge are compensated for by reduction factors, and the guidelines will accordingly be set below the thresholds of critical effects. Some of the immediate effects can be quantified with reasonable precision, and derivation of guidelines will not require a substantial reduction below the observed threshold levels. When the precision and certainty of the relationship between exposure and adverse outcome is lower, a larger reduction may be warranted. There is no definite basis for determining the precise magnitude of the reduction factors, and the choice of the reduction is a matter of scientific judgement. As with all the procedures, setting reduction factors should be free of vested commercial interest
Some examples of sources of uncertainty about exposure-effect threshold levels include the extrapolation of animal data to effects on humans, differences in the physiological reserves of different people with corresponding differences in tolerance, and statistical uncertainties (confidence limits) in the dose-response function. In ICNIRP’s view, uncertainty in measurements used to implement the guidelines is a problem more appropriate to the functions of organizations responsible for the development of compliance methods.
It is not considered in the setting of reduction factors by ICNIRP. It should be noted that the use of reference levels may, in many cases, result in additional reductions as they correspond to basic restrictions only under maximum absorption or coupling. |
降低影響閾值以補償導則制定過程中各種不確定源的影響。
當曝露和不良後果之間的關係的正確與確定是較低的，較大的降低可能有必要。沒有明確的基礎上決定精確幅度的減少因素，選擇減少的幅度是一個科學判斷的問題。
一些曝露影響閾值水平不確定源的例子包括： 將動物影響數據外推到對人的影響；不同人由於耐受性差異造成的生理學儲備的差異和劑量-反應關系統計上的不確定性（置信區間）。在ICNIRP 看來，應用導則時的測量不確定性對負責提出相符性方法的機構而言是更現實的問題。ICNIRP 在設定降低因子中沒有考慮這一點。
(註:環保署誤導如下: …為了顧慮暴露之健康風險，分別對一般民眾暴露限值(即每日24小時暴露)已納入50倍的折減係數考量；職業人員暴露限值(即每日少於8小時之暴露) 已納入10倍的折減係數考量) |
| WHO 2002年「ESTABLISHING A DIALOGUEON RISKS FROM ELECTROMAGNETIC FIELDS」 Exposure limits are based on effects related to short-term acute exposure rather than long-term exposure, because the available scientific information on the long-term low level effects of exposure to EMF fields is considered to be insufficient to establish quantitative limits. ICNIRP uses a reduction factor of 10 to derive occupational limits for workers and a factor of about 50 to arrive at exposure limits for the general public. The occupationally exposed population consists of adult workers who are generally aware of electromagnetic fields and their effects. Workers are trained to be aware of potential risk and to take appropriate precautions. By contrast, the general public consists of individuals of all ages and of varying health status who, in many cases, are unaware of their exposure to EMF.
In addition, workers are typically exposed only during the working day (usually 8 hours per day) while the general public can be exposed for up to 24 hours per day. These are the underlying considerations that lead to more stringent exposure restrictions for the general public than for the occupationally exposed population. | WHO 2002年「ESTABLISHING A DIALOGUEON RISKS FROM ELECTROMAGNETIC FIELDS」 導則的依據是甚麼? 暴露限值是基於短期急性暴露而不是長期暴露的影響，因為有關電磁場長期、低水平暴露的可用科學信息被認為不足以制定量化限值。 ICNIRP使用了10倍的降低因子而得出職業暴露限值，使用了50倍的降低因子而得出公眾暴露限值，限值隨頻率不同而變化，因此低頻場(如電力線路)和高頻場(如移動電話)的限值不同。 職業暴露人群由已經普遍認識到電磁場及其影響的成年工作人員組成。這些工作人員經過培訓，知道潛在的風險和應採取的適當防範措施。相較之下，普通公眾中包含了年齡層次和健康狀況各樣的人，在很多情況下，他們不知道自己暴露在電磁場中。 另外，工作人員一般僅在工作日才受到暴露(通常每天8小時)，而普通公眾的暴露時間則可能達到每天24小時)，
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| (2010 ICNIRP p824) GUIDELINES FOR LIMITING EMF EXPOSURE Separate guidance is given for occupational exposures and exposure of the general public. Occupational exposure in these guidelines refers to adults exposed to time-varying electric, and magnetic fields from 1 Hz to 10 MHz at their workplaces, generally under known conditions, and as a result of performing their regular or assigned job activities. By contrast, the term general population refers to individuals of all ages and of varying health status which might increase the variability of the individual susceptibilities. In many cases, members of the public are unaware of their exposure to EMF. These considerations underlie the adoption of more stringent exposure restrictions for the public than for workers while they are occupationally exposed.
Addressing scientific uncertainty All scientific data and their interpretation are subject to some degree of uncertainty. Examples are methodological variability and inter-individual, inter-species, and inter-strain differences. Such uncertainties in knowledge are compensated for by reduction factors. There is, however, insufficient information on all sources of uncertainty to provide a rigorous basis forestablishing reduction factors over the whole frequency range and for all modulation patterns. Therefore, the degree to which caution is applied in the interpretation of the available database and in defining reduction factors is to a large extent a matter of expert judgment. | (2010 ICNIRP p824) 限制電磁場曝露的導則
對職業曝露和公眾曝露分別給出指南。
本導則推薦的職業曝露限 值適用於在他們的工作場所曝露於1Hz 到10MHz 時變電場和磁場的成人，通常是在已知情況下完成他們常規或指定的職業行為；而 “公眾”則是指所有年齡和不同健康狀況、在個體敏感性方面可能具有較高可變性的個體。在很多情況下，公眾成員不知道曝露於電磁場。這種考慮突出了對公眾比對在職業曝露下的工作人員採取了更嚴格的曝露限制。
科學不確定性的處理
所有科學數據及其解釋都會存在一定程度的不確定性。例如研究方法差異以及個體間、樣本間及種族間的差異。這些知識上的不確定性都採用“降低因子”來補償。但是針對所有的不確定源要給出嚴格的依據，來對全頻段和對所有的控制類型給出降低因子，所需要的信息還是不充分的。因此，在解釋可用的數據庫中數據以及確定降低因子時採取多大的謹慎程度，在很大程度上取決於專家判斷。 |
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| (2010 ICNIRP p818)
SCOPE AND PURPOSE The main objective of this publication is to establish guidelines for limiting exposure to electric and magnetic fields (EMF) that will provide protection against all established adverse health effects. Studies on both direct and indirect effects of EMF have been assessed: direct effects result from direct interactions of fields with the body; indirect effects involve interactions with a conducting object where the electric potential of the object is different from that of the body. Results of laboratory and epidemiological studies, basic exposure assessment criteria, and reference levels for practical hazard assessment are discussed, and the guidelines presented here are applicable to both occupational and public exposure.
The restrictions in these guidelines were based on established evidence regarding acute effects; currently available knowledge indicates that adherence to these restrictions protect workers and members of the public from adverse health effects from exposure to low frequency EMF. The epidemiological and biological data concerning chronic conditions were carefully reviewed and it was concluded that there is no compelling evidence that they are causally related to low-frequency EMF exposure. | (2010 ICNIRP p818)
範圍與目的 本出版物的主要目的是建立限制電場、磁場（EMF）曝露的導則， 它將為防止所有已確定的有害健康的影響提供保護。已經對EMF 直接和間接影響的研究進行了評估：直接影響是源於場與人體的直接作用；非直接影響包括與導電物體（該物體所具有的電位與人體不同）的相互作用。 對實驗室及流行病學研究結果、基本曝露評估判據以及用於實際危害評估的參照水平等進行了討論。所提出的導則既適用於職業也適用於公眾曝露。
導則的限值是基於已確定的關於急性效應的證據；現有的可用的 知識指出，遵循這些限值可保護職工和公眾免受低頻電磁場曝露的有害健康影響。非常小心地複核了流行病學和生物學數據，結論是：沒有充分的證據表明它們與低頻電磁場曝露有因果關系。 |
| (2010 ICNIRP p818) As detailed below, the basis for the guidelines istwo-fold: Exposure to low-frequency electric fields may cause well-defined biological responses, ranging from perception to annoyance, through surface electric-charge effects. In addition, the only well established effects in volunteers exposed to low frequency magnetic fields are the stimulation of central and peripheral nervous tissues and the induction in the retina of phosphenes, a perception of faint flickering light in the periphery of the visual field. The retina is part of the CNS and is regarded as an appropriate, albeit conservative, model for induced electric field effects on CNS neuronal circuitry in general. In view of the uncertainty inherent in the scientific data, reduction factors have been applied in establishing the exposure guidelines. For details see ICNIRP 2002 | (2010 ICNIRP p818) 如下所詳述， 導則的基礎來自兩個方面： 一是低頻電場曝露引起 的已被很好識別的生物反應，這些反應是通過表面電荷作用，其程度從有感覺到煩惱。
二是通過曝露在低頻磁場的志願者實驗而確認的唯一影響，即中樞神經和周圍神經組織刺激以及視網膜光幻視的感應，也即在視場周圍的一種昏暈閃爍光感覺。視網膜是中樞神經系統的一部分，雖然用於中樞神經系統神經元回路感應電場效應的模型略顯保守，但總體還是合適的。 鑒於科學數據中仍存在的不確定性，本曝露導則已應用了降低因子（reduction factors）。詳細可見 ICNIRP2002 |
| (2010 ICNIRP p824) In recent years, more realistic calculations based on anatomically and electrically refined heterogeneous models (Xi and Stuchly 1994; Dimbylow 2005, 2006; Bahr et al. 2007) resulted in a much better knowledge of internal electric fields in the body from exposure to electric and magnetic fields. The most useful dosimetric results for the purpose ofthese guidelines have been obtained from high resolution calculations of induced electric field with voxel sizes below 4 mm (Dimbylow 2005; Bahr et al. 2007; Hirata et al. 2009; Nagaoka et al. 2004). The maximum electric field is induced in the body when the external fields are homogeneous and directed parallel to the body axis (E-field) or perpendicular (H-field). According to those calculations, the maximum local peak electric field induced by a 50 Hz magnetic field in the brain is approximately 23–33 mV m_1 per mT, depending on field orientation and body model. There is no conversion factor for peripheral nerve tissue available at present. Therefore, the skin, which contains peripheral nerve endings, was chosen as a worst-case target tissue. The electric field induced in the skin by such a field is approximately 20–60 mV m-1 per mT. The maximum local electric field induced by a 50 Hz electric field in the brain is approximately 1.7–2.6 mV m-1 per kV m-1, while in the skin it is approximately 12–33 mV m-1 per kV m-1. In view of the uncertainties in the available dosimetry as well as the influence of body parameters in the derivation of reference levels, ICNIRP is taking a conservative approach in deriving reference levels from the basic restrictions. | (2010 ICNIRP p824) 近年來，基於解剖學和電學改良的非均質模型（Xi and Stuchly 1994,Dimbylow 2005 and 2006,Bahr et al 2007）可使人們對曝露在電場和磁場中的體內原位電場有更好的認識，實施與事實更加相符的計算。 修訂本導則的最有用的劑量學結果，是通過體素小於4mm 的感應電場的高分辨率數值模擬得出的（Dimbylow 2005 ,Bahr et al 2007；Hirata et al 2009；Nagaoka et al 2004）。體內最大感應電場出現在外部場均勻且其朝向與體軸平行（E 場）或者垂直（H 場）時。根據這些計算結果，隨場的方向和人體模型不同，由每mT 50Hz 磁場在腦中感應的最高局部峰值電場的值約為23~33 mV m-1。對周圍神經組織，目前還沒有可用的轉換系數，因而選擇包含周圍神經末梢的皮膚作為最壞情況下的目標組織。由每mT 上述場在皮膚感應的電場約為20~60 mV m-1。每kV m-1 的50Hz 電場在腦中引起的最大局部電場約為1.7~2.6mV m-1。而每kV m-1 的50Hz 電場在皮膚引起的最大局部電場約為12~33 mV m-1。 從现有計量學數據的不確定性以及在導出參照水平時人體參數的影響出發，ICNIRP 在由基本限值導出參照水平時採取了保守的處理。 |
| (2010 ICNIRP p824.825) Basic restrictions and reference levels
Limitations of exposure that are based on the physical quantity or quantities directly related to the established health effects are termed basic restrictions. In this guideline, the physical quantity used to specify the basic restrictions on exposure to EMF is the internal electric field strength Ei, as it is the electric field that affects nerve cells and other electrically sensitive cells.
The internal electric field strength is difficult to assess. Therefore, for practical exposure assessment purposes, reference levels of exposure are provided. Most reference levels are derived from relevant basic restrictions using measurement and/or computational techniques but some address perception (electric field) and adverse indirect effects of exposure to EMF. The derived quantities are electric field strength (E), magnetic field strength (H), magnetic flux density (B) and currents flowing through the limbs (IL). The quantity that addresses indirect effects is the contact current (IC).
In any particular exposure situation, measured or calculated values of any of these quantities can be compared withthe appropriate reference level. Compliance with the reference level will ensure compliance with the relevant basic restriction. If the measured or calculated value exceeds the reference level, it does not necessarily follow that the basic restriction will be exceeded. However, whenever a reference level is exceeded it is necessary to test compliance with the relevant basic restriction and to determine whether additional protective measures are necessary. | (2010 ICNIRP p824.825) 基本限值和參照水平
根據軀體内物理量或與已確定的健康影響直接有關的量制定的曝露限值稱之為“基本限值”。在本導則中，用來規定電磁場曝露基本限值的物理量是體內電場強度Ei ，這是由於是電場對神經細胞和其它電氣敏感細胞產生影響。
由於體內電場強度難以實測評價，因此從實際曝露評估出發，提供了曝露的參照水平。來確定是否符合或者超過基本限值。大多數參照水平是從相關的基本限值，採用測量和/或計算技術導出，但也有一些參照水平是用電磁場曝露的感覺（電場）和有害的非直接影響表達的。導出的量是電場（E）、磁場強度（H）、磁通密度（B）和流過肢體的電流（IL）。表達非直接影響的量是接觸電流（IC）。
在任何特定曝露情況下，任何測量或計算得到的值可以與適當的參照水平相比較。符合參照水平就能確保符合相應的基本限值。假如測量或計算值超過參照水平，不一定就等於基本限值已超過。但是，在超過參照水平時，有必要檢驗與相應的基本限值的相符性，並確定是否有必要採取附加的防護措施。 |
| (2010 ICNIRP p824.825) BASIC RESTRICTIONS The main objective of this publication is to establish guidelines for limiting EMF exposure that will provide protection against adverse health effects. As noted above, the risks come from transient nervous system responses including peripheral (PNS) and central nerve stimulation (CNS), the induction of retinal phosphenes and possible effects on some aspects of brain function.
In view of the considerations above for frequencies in the range 10 Hz to 25 Hz, occupational exposure should be limited to fields that induce electric field strengths in CNS tissue of the head (i.e., the brain and retina) of less than 50 mV m_1 in order to avoid the induction of retinal phosphenes. These restrictions should also prevent any possible transient effects on brain function. These effects are not considered to be adverse health effects; however, ICNIRP recognizes that they may be disturbing in some occupational circumstances and should be avoided but no additional reduction factor is applied. Phosphene thresholds rise rapidly at higher and lower frequencies, intersecting with the thresholds for peripheral and central myelinated nerve stimulation at 400 Hz. At frequencies above 400 Hz, limits on peripheral nerve stimulation apply in all parts of the body. Exposure in controlled environments, where workers are informed about the possible transient effects of such exposure, should be limited to fields that induce electric fields in the head and body of less than 800 mVm_1 in order to avoid peripheral and central myelinated nerve stimulation. A reduction factor of 5 has been applied to a stimulation threshold of 4 V m_1 in order to account for the uncertainties described above.Such restrictions rise above 3 kHz.
For the general public for CNS tissue of the head a reduction factor of 5 is applied, giving a basic restriction of 10 mV m_1 between 10 and 25 Hz. Above and below these values, the basic restrictions rise. At 1,000 Hz it intersects with basic restrictions that protect against peripheral and central myelinated nerve stimulation. Here, the reduction factor of 10 results in a basic restriction of 400 mV m_1, which should be applied to the tissues of all parts of the body. | (2010 ICNIRP p824.825) 基本限值 本出版物的主要目的是建立防止有害健康影響的限制電磁場曝露的導則。如上所述，風險來自短暫的神經系統響應，包括對周圍神經（PNS）和中央神經（CNS）的刺激、視網膜光幻視和對腦功能一些方面的可能影響。
根據以上考慮，對頻率範圍從10Hz 到25Hz，職業曝露應限制頭部中央神經系統組織（即腦和視網膜）中感應電場強度不超過50 mVm-1，以避免視網膜光幻視。該限值也應能防止任何對腦功能可能的暫時影響，這些影響並不認為是有害的健康影響；但是，ICNIRP 認為它們可能在某些職業情況下形成干擾，應該予以避免，但是不對此附加專門的降低因子。在較高和較低頻率，光幻視閾值迅速提高，在400 Hz 頻率，光幻視閾值與對周圍和中央有髓神經刺激的閾值曲線相交。在頻率400 Hz 以上，周圍神經刺激的閾值適用於身體的所有部位。
在受控環境中的曝露，工人被告知這樣的曝露可能有暫時效應，為了避免周圍和中央有髓神經刺激，應限制頭部和軀體內感應電場不超過800 mV m-1。該值是考慮了以上所述的不確定性，對於周圍神經刺激閾值4 V m-1而言，賦予了5 倍降低因子。該限值在頻率超過3KHz時上升。
對公眾而言，針對頭部的中央神經組織應用了5 倍的降低因子， 得出曝露基本限值在10 到25Hz 為10 mV m-1。高於或低於上述頻率，基本限值提高。在1000Hz 頻率,曲線與防止周圍和中央有髓神經刺激的基本限值曲線相交。在此點，與基本限值400 mV m-1 相比，有10倍的降低因子，它適用於身體所有部位的組織。 |
| (2010 ICNIRP p825) Time averaging ICNIRP recommends that the restrictions on internal electric fields induced by electric or magnetic fields including transient or very short-term peak fields be regarded as instantaneous values which should not be time averaged (see also section on non-sinusoidal exposure). | (2010 ICNIRP p825) 時間平均 對包括暫態或非常短期峰值的電場或磁場，ICNIRP 推薦的體內電場限值應看作瞬時值而不應是時間平均值（參見非正弦曝露節） |
| (2010 ICNIRP p826,827) REFERENCE LEVELS The reference levels are obtained from the basic restrictions by mathematical modeling using published data (Dimbylow 2005, 2006). They are calculated for the condition of maximum coupling of the field to the exposed individual, thereby providing maximum protection. Frequency dependence and dosimetric uncertainties were taken into account.
The reference levels presented consider two distinct effects and approximate a combination of the induced electric fields in the brain, relevant for CNS effects, and the induced electric fields in non-CNS tissues anywhere in the body, relevant for PNS effects (i.e., at 50 Hz, the factor used to convert the basic restriction for CNS effects to an external magnetic field exposure is 33 V m_1 per T, and for PNS effect 60 V m_1 per T. An additional reduction factor of 3 was applied to these calculated values to allow for dosimetric uncertainty). In addition, the electric field reference level for occupational exposure up to 25 Hz includes a sufficient margin to prevent stimulation effects from contact currents under most practical conditions. Between 25 Hz and 10 MHz the reference levels are based on the basic restriction on induced electric fields only and might thus not provide a sufficient margin to prevent stimulation effects from contact currents under all possible conditions in that frequency band. The electric field reference levels for general public exposure up to 10 MHz prevent adverse indirect effects (shocks and burns) for more than 90% of exposed individuals. In addition, the electric field reference levels for general public exposure up to 50 Hz include a sufficient margin to prevent surface electric-charge effects such as perception in most people.
Tables 3 and 4 summarize the reference levels for occupational and general public exposure, respectively, and the reference levels are illustrated in Figs. 2 and 3. The reference levels assume an exposure by a uniform (homogeneous) field with respect to the spatial extension of the human body. | (2010 ICNIRP p826,827) 參照水平 參照水平是通過數學模型、使用已發布的數據，由基本限值獲得 （Dimbylow2005，2006）。它們是按照場對人體曝露最大耦合條件計算得到的，因而可提供最大保護。考慮了頻率相關性和劑量不確定性。
所提出的參照水平考慮了兩種不同的效應和腦中感應電場的近似綜合性。既有與中樞神經系統效應（以及在體內非9中樞神經系統組織內的感應電場）的關系，又有與周圍神經系統的關系 （即：在50Hz，用於把對中樞神經系統影響的基本限值轉換到外磁場曝露的系數為每T 相當於 33 V m-1，而對周圍神經系統影響的系數為每T 相當於60 V m-1。考慮劑量的不確定性，對這些計算值賦予了3 倍的附加降低因子）。
另外，25 Hz 及以下職業曝露的電場參照水平包含了足夠的安全裕度來預防所有可能情況下的接觸電流刺激效應。 在25 Hz 和10 MHz 範圍內，參照水平根據感應電場的基本限值制定，這樣，在該頻段內就有可能沒有提供足夠的安全裕度來防止所有可能條件下接觸電流的刺激效應。
對10 MHz 及以下的公眾曝露電場參照水平可使90%以上的受曝露個體免受有害的非直接影響（電擊和灼痛）。另外，50 Hz 及以下公眾曝露參照水平包含足夠的裕度避免表面電荷效應（比如大多數人的感覺）。
表3 和表4 分別匯總了職業和公眾曝露的參照水平，上述參照水平分別在圖2 及圖3 中畫出。參照水平是假設在人體所在空間範圍內，受曝露的場是均勻的。 |
| (2010 ICNIRP p827) Spatial averaging of external electric and magnetic fields For a very localized source with a distance of a few centimeters from the body, the only realistic option for the exposure assessment is to determine dosimetrically the induced electric field, case by case. When the distance exceeds 20 cm, the distribution of the field becomes less localized but is still non-uniform, in which case it is possible to determine the spatial average along the body or part of it (Stuchly and Dawson 2002; Jokela 2007). The spatial average should not exceed the reference level. The local exposure may exceed the reference level but with an important provision that the basic restriction shall not be exceeded. It is the task of standardization bodies to give further guidance on the specific exposure situations where the spatial averaging can be applied. This guidance shall be based on well established dosimetry. The standardization bodies also may derive new reference levels for special types of non-uniform exposure.
| (2010 ICNIRP p827) 外部電場和磁場的空間平均
對於離人體數厘米的非常局限的源，曝露評估唯一可靠的方法是針對具體案例逐個確定感應電場的劑量。當距離超過20 厘米時，場的分布就變得不那麼局限，但仍是不均勻的，在這種情況下，沿軀體或軀體的一部分確定空間平均是可行的（Stuchly and dawson 2002；Jokela 2007）。空間平均不應超過參照水平。局部曝露可以超过参照水平，但有一個重要的前提，即基本限值不應被超過。對運用空間平均的特殊曝露情況給出進一步的指南是標准化組織的任務。本導則是依據良好確定的劑量學結果。標准化組織也可針對特定類型的非均勻曝露給出新的參照水平。
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| 2010 ICNIRP p828 REFERENCE LEVELS FOR CONTACT CURRENTS Up to 10 MHz reference levels for contact current are given for which caution must be exercised to avoid shock and burn hazards. The point contact reference levels are presented in Table 5. Since the threshold contact currents that elicit biological responses in children are approximately one-half of those for adult men, the reference levels for contact current for the general public are set lower by a factor of 2 than the values for occupational exposure. It should be noted that the reference levels are not intended to prevent perception but to avoid painful shocks. Perception of contact current is not per se hazardous but could be considered as annoyance.Prevention of excess contact currents is possible by technical means. | 2010 ICNIRP p828 接觸電流的參照水平
給出了 10MHz 及以下接觸電流的參照水平，必須對此采取謹慎措施以避免電擊和灼傷的危害。點接觸的參照水平列於表5。由於兒童誘發生物學響應的接觸電流閾值約是成年男子的1/2，因此對公眾的接觸電流參照水平設定得比職業曝露限值低1 倍。應指出，參照水平的目的並非是防止感覺（perception），而是為了避免痛感的電擊（painful shocks）。接觸電流的感覺本身不是一種危害，但可考慮為一種煩惱。防止超過接觸電流可以通過技術手段來實現。 |
| 2010 ICNIRP p835 Established mechanism A bioelectric mechanism having the following characteristics: (a) can be used to predict a biological effect in humans; (b) an explicit model can be made using equations or parametric relationships; (c) has been verified in humans, or animal data can be confidently extrapolated to humans; (d) is supported by strong evidence; and (e) is widely accepted among experts in the scientific community. | 2010 ICNIRP p833 已確定的機制 Established mechanism 具有以下特性的生物電機制： （a）能用於預測人體的生物效應；（b）通過方程或參數關系可以建立具體的模型； （c）已經在人體中得到證實或者動物數據能可信地外推到人體上； （d）有強證據支持； （e）被科學界專家廣泛接受。 |
| 2010 ICNIRP p832 Basic restrictions Mandatory limitations on the quantities that closely match all known biophysical interaction mechanisms with tissue that may lead to adverse health effects. | 2010 ICNIRP p832 基本限值 Basic restriction 與所有已知的、可能導致人體組織有害健康影響的生物作用機制密切相關的定量的、必須遵循的限值。 |
| 2010 ICNIRP p835 Reduction factor Reduction of the effect threshold to compensate for various sources of uncertainty in the guideline setting process. Some examples of sources of uncertainty about exposure-effect threshold levels include the extrapolation of animal data to effects on humans, differences in the physiological reserves of different people with corresponding differences in tolerance, and statistical uncertainties (confidence limits) in the dose-response function. In ICNIRP’s view, uncertainty in measurements used to implement the guidelines is a problem more appropriate to the functions of organizations responsible for the development of compliance methods. It is not considered in the setting of reduction factors by ICNIRP.
| 2010 ICNIRP p835 降低因子 Reduction factor 降低影響閾值以補償導則制定過程中各種不確定源的影響。一些曝露影響閾值水平不確定源的例子包括：將動物影響數據外推到對人的影響；不同人由於耐受性差異造成的生理學儲備的差異和劑量-反應關系統計上的不確定性（置信區間）。 在ICNIRP 看來，應用導則時的測量不確定性對負責提出相符性方法的機構而言是更現實的問題。ICNIRP 在設定降低因子中沒有考慮這一點。
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| 2010 ICNIRP p835 Reference levels The rms and peak electric and magnetic fields and contact currents to which a person may be exposed without an adverse effect and with acceptable safety factors. The reference levels for electric and magnetic field exposure in this document may be exceeded if it can be demonstrated that the basic restrictions are not exceeded. Thus, it is a practical or “surrogate” parameters that may be used for determining compliance with the Basic Restrictions. | 2010 ICNIRP p835 參照水平 Reference levels 人體可能曝露而無有害影響，並帶有可接受的安全因子的電場、磁場和接觸電流的有效值及峰值。如果能證明沒有超出基本限值，本導則中的電場和磁場曝露的參照水平可以超過。 因此，它是可以用來確定與基本限值相符性的適用或“替代”的參數 |
| WHO 2006 Framework for Developing health-based electromagnetic fields standards (p25)
1.1 G uiding principles WHO encourages the establishment of exposure limits and other control measures that provide the same or similar level of health protection for all people. It endorses the guidelines of the International Commission on Non-Ionizing Radiation Protection (ICNIRP) and encourages Member States to adopt these international guidelines. However, if a Member State wants to develop its own standards, this Framework can be used as a guide. | WHO 2006 Framework for Developing health-based electromagnetic fields standards (p25) 1.1 導則原則 世界衛生組織鼓勵建立能向全人類提供相同或相似健康保護水平的暴露限值及其他控制措施。它批准國際非游離輻射防護委員會(ICNIRP)導則，並鼓勵成員國採納這些國際性的導則。但是，如果某個成員國需要制定他們自己的標準，本框架可做為指導。 |
| WHO 2006 Framework for Developing health-based electromagnetic fields standards
4.5 Exp osure standards requirements To ensure that an exposure standard has all the elements necessary to be complete, the following points must be addressed: Exposure level: the level of exposure can be practically expressed in terms of reference levels. Situations where simultaneous exposure can occur to multiplefrequency fields must be accounted for in the standard. Exposure duration: the time of exposure to various power levels should be quite precise. In many standards a certain power level is set for continuous exposure for 8 or 24 h per day, but higher levels of exposure are generally permitted for short periods of time. In this respect, the time over which the exposure level is averaged is important. The exact means of averaging exposures must be clearly indicated so that no confusion arises in the minds of persons responsible for compliance. | WHO 2006 Framework for Developing health-based electromagnetic fields standards(制定以健康為基礎的EMF標準的框架)
4.5 暴露標準制定的要求 為確保暴露標準所有要素的完整，以下幾點必須注意:
暴露水平: 在實際應用中，可以用參照水平來表示暴露水平。多個頻率場同時暴露的情況必須在標準中有所說明。
暴露持續時間: 不同能量水平的暴露時間應該是十分確切的。在很多標準中，確定的能量水平是針對8-24小時/天的暴露時間，但在更高的暴露水平，通常只允許更短的暴露時間，在這方面，暴露水平的時間平均是很重要的。應明確地指出平均暴露的含義，以使有責任執行標準的人不產生理解的混淆。
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| WHO 2006 Framework for Developing health-based electromagnetic fields standards(制定以健康為基礎的EMF標準的框架)
| WHO 2006 Framework for Developing health-based electromagnetic fields standards(制定以健康為基礎的EMF標準的框架)
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| This approach requires a good understanding of the interaction mechanisms involved and supposes that a true threshold exists. It also assumes that cumulative effects do not occur(此方法假設累積效應不存在). Evidence for cumulative damage would need to show that small amounts of damage may be occurring from low level (sub-threshold) exposure and that an accumulation of this damage is necessary before it becomes detectable.(而且這種危害的累積在可能被檢出前是無法避免的) Further, there is a dependence on information from extensive research, including long-term followup studies. Without such studies, it is possible that illnesses or effects which manifest themselves after a long latency period would be excluded from consideration.(疾病或是經過長時間潛伏期後才顯露出來的健康影響可能會被排除在考慮之外) (p21)
| 這方法要求對所涉及的作用機制有足夠的了解，並且推測存在確實的閾值。該方法 假設累積效應不存在的。需要有累積危害的證據來顯示有少量的危害可能由低水平的暴露(次閾值)引起，而且這種危害的累積在可能被檢出前是無法避免的。此外，還須依靠更深入的研究，包括長期的跟蹤研究，沒有這樣研究，疾病或是經過長時間潛伏期後才顯露出來的健康影響可能會被排除在考慮之外
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| 4.3 B asic restrict ions and reference levels (p23) Limits on EMF exposure are termed basic restrictions and are based directly on established health effects and biological considerations. The physical quantities used in the international guidelines reflect the different concepts of “dose” relevant to the lowest-threshold for a health effect at different frequencies.
| 電磁場暴露現值所定義的”基本現值”是直接建立在健康影響以及生物考慮的基礎之上。
國際導則中使用的物理量反映了與不同頻率下健康影響最低閾值相關的不同的”劑量”觀念
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| In the low frequency range (between 1 Hz and 10 MHz) the current basic restriction is the current density (J, in A m-2) for preventing effects in excitable tissues such as nerve and muscle cells; and in the high frequency range (between 100 kHz and 10 GHz), the basic restriction is the specific absorption rate (SAR, in W kg-1) for prevention of whole-body heat stress and local heating. In the intermediate frequency range (between 100 kHz and 10 MHz)restrictions are on both the current density and SAR, while in the very high frequency range (between 10 and 300 GHz) the basic restriction is the incident power density (S, in W m-2) for excessive tissue heating near or at the body surface. Protection against known acute adverse health effects is assured if these basic restrictions are not exceede
| 在極低頻範圍(1 Hz and 10 MHz)，電流的基本限值是電流密度(J, in A m-2)，它是為了防止在易激勵組織(如神經和肌肉細胞)中的影響
在高頻範圍(1 00KHz ~ 10GHz)，基本限值是比吸收率(SAR, WKg-1)，它是為了防止全身熱應力和局部加熱的。
在中頻範圍(1 00KHz ~10 MHz)，其限值是電流密度和SAR兩者。
而在很高的頻率範圍(1 0GHz ~300 GHz)下，基本限值是入射功率密度(S, W m-2)，它是為了防止全身熱應力和局部加熱的。 (J, in A m-2)，它是為了防止鄰近或表皮上的組織過熱。
只要不超出這些基本限值，就確認不會發生已知的急性有害健康影響。 |
| Because basic restrictions are often specified as quantities that may be impractical to measure, other quantities are introduced for practical exposure assessment purposes to determine whether the basic restrictions are likely to be exceeded. These reference levels (ICNIRP) or maximum permissible exposure levels (IEEE) correspond to basic restrictions under worst case exposure conditions for one or more of the following physical quantities: electric field strength (E), magnetic field strength (H), magnetic flux density (B), power density (S), limb current (IL), contact current (Ic) and, for pulsed fields, specific energy absorption (SA). Exceeding the reference levels does not necessarily imply that the basic restrictions are exceeded. However, in this case, it is necessary to test compliance with the relevant basic restrictions and to determine whether additional protective measures are necessary.
| 由於基本限值通常是一個難以測量的量，因此把其他一些量引入到實際曝露評估中，用以確定基本限值是否可能超出。這些“參照水平”(ICNIRP)或“最大許可曝露水平”(IEEE)對應於在最不利的曝露條件下的基本限值。這些物理量是：電場強度(E)，磁場強度(H)，磁通密度(B)，功率密度(S)，肢體電流(IL)，接觸電流(Ic)以及脈衝場的比能量吸收(SA)。超過參照水平並不表示就一定超出了基本限值。但在這樣的情況下，必須檢測與相關的基本限值相符性並且確定是否需要附加的保護措施
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Some standards make provisions for occupationally exposed women who are pregnant to be considered as general public for the purpose of exposure limits. An example of how a national authority has managed this issue comes from the Australian RF standard (RPS3, http://www.arpansa.gov.au/rps_pubs.htm): “In order to reduce the risk of accidental exposure above occupational limits a pregnant woman should not be exposed to levels of RF fields above the limits of general public exposure. Occupationally exposed women who are pregnant should advise their employers when they become aware of their pregnancy. After such notification, they must not be exposed to RF fields exceeding the general public limits. Pregnancy should lead to implementation of relevant personnel policies. These include, but are not limited to, reasonable accommodation/adjustment or temporary transfer to non- RF work without loss of employment benefits.”
| 有一些標準把懷孕中的職業婦女的曝露限值歸類為“公眾”。以下是來自澳大力亞RF標準(RPS3，http://www/arpansa.gov.au/rps_pubs.htm)，體現國家權力機構如何管理這一問題的例子：“為了減少高於職業曝露限值的意外曝露限值的射頻(RF)場中。當職業曝露婦女得知自己懷孕後，應及時將這一情況告知雇主。在告知後，她們不能曝露於超過普通公眾曝露限值的射頻(RF)場中。職業曝露婦女懷孕後應值執行相關的人事政策，包括(但不限於)合理的通融/調節甚至臨時調動制沒有射頻(RF)場的工作，而且不會損失薪資福利。”
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| 5.3 Precautionary aspect s (p28) The existence of well-established adverse health effects forms the basis of current EMFexposure guidelines. The increasing awareness of the need to account for uncertainty in the science database has been addressed primarily through research. However, research programmes may take several years to complete, and the long latency associated with diseases such as cancer in people may also preclude a rapid outcome in some studies.
The issue of current uncertainty is addressed by some countries that wish to be more protective by requiring that exposures be reduced or avoided where possible. While EMF standards include exposure limits, some authorities now also have additional measures. Examples of such measures for ELF fields from power lines include minimum height of electrical conductors and necessary clearance between a transmission line and buildings (more specifically schools). For RF fields, restrictions on the siting of base stations, mandatory specifications for mobile phones and recommendations for use of handsfree-kits have been provided by different authorities. |
已確認的有害健康影響的存在，形成了當前EMF曝露導則的基礎。
要求考慮科學數據不確定性的關注日益增長，已被列為優先研究。但是研究的過程可能需要幾年才能完成，而且一些疾病的潛伏期比較久(例如癌症等)，也排除了一些研究很快得出結果的可能性。
目前的不確定性問題在一些國家表現為希望通過盡可能降低或避免暴露來強化保護。在EMF標準已包含曝露限值的情況下，一些政府機構採取了另外的措施，
例如對輸電線路極低頻場的措施包括限制導體的最低高度以及輸電線和建築物之間(特別是學校)必要的距離等。對於射頻場，不同的政府機構提供了諸如基站選址的限制、移動電話的強制規範以及使用免提設備的建議等。
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