電磁波與公眾健康-世界衛生組織304號文件

電磁波與公眾健康
Electromagnetic fields and public health
基地台及無線技術
Base stations and wireless technologies

世界衛生組織304號文件(Fact sheet N304)
發表日期：2006年5月(May 2006)
　　
行動通訊已經普及於世界各地，這些無線技術須仰賴基地台(Base Station) 或固定天線所組成的大規模網路，發射射頻(RF)訊號以進行通訊。目前全球基地台總數超過140萬台，而隨著第三代行動通訊（3G）技術的引進，基地台的數量也將顯著增加。

Mobile telephony is now commonplace around the world. This wireless technology relies upon an extensive network of fixed antennas, or base stations, relaying information with radiofrequency (RF) signals. Over 1.4 million base stations exist worldwide and the number is increasing significantly with the introduction of third generation technology.

在住家、辦公室與許多公共場合（機場、學校、住宅與都會區），提供高速上網和服務的其他無線網路，如無線區域網路（WLAN）也越來越普遍。隨著基地台和無線網路的成長，公眾在射頻訊號的暴露值也隨之增加。根據最新的調查顯示，基地台之射頻訊號暴露值，為國際暴露值標準的0.002%到2%，視天線的距離、周遭環境等多項因素而定，此暴露值低於或相當於廣播或電視電台的射頻訊號暴露值。

Other wireless networks that allow high-speed internet access and services, such as wireless local area networks (WLANs), are also increasingly common in homes, offices, and many public areas (airports, schools, residential and urban areas). As the number of base stations and local wireless networks increases, so does the RF exposure of the population. Recent surveys have shown that the RF exposures from base stations range from 0.002% to 2% of the levels of international exposure guidelines, depending on a variety of factors such as the proximity to the antenna and the surrounding environment. This is lower or comparable to RF exposures from radio or television broadcast transmitters.

有人憂慮暴露在無線科技射頻訊號的電磁場強下，可能會對健康造成影響。本文件即以科學證據探討人體持續暴露在基地台與其他區域無線網路下，是否會對人體健康產生影響。

There has been concern about possible health consequences from exposure to the RF fields produced by wireless technologies. This fact sheet reviews the scientific evidence on the health effects from continuous low-level human exposure to base stations and other local wireless networks.

健康顧慮Health concerns
　　
基地台和區域網路天線可能使全身長期暴露在射頻領域下，是否對健康造成影響，這是一個常見的顧慮。但到目前為止，科學證據指出，射頻領域唯一的健康效應為體溫升高（大於攝氏一度），而且只有在特定工業用的射頻強度，如傳播射頻訊號加熱器(RF heaters)才會發生。基地台和無線網路的射頻訊號暴露值極低，人體上升的溫度根本微不足道，不會影響人體健康。

A common concern about base station and local wireless network antennas relates to the possible long-term health effects that whole-body exposure to the RF signals may have. To date, the only health effect from RF fields identified in scientific reviews has been related to an increase in body temperature (> 1 °C) from exposure at very high field intensity found only in certain industrial facilities, such as RF heaters. The levels of RF exposure from base stations and wireless networks are so low that the temperature increases are insignificant and do not affect human health.

射頻訊號電磁場強度在發射源處最高，且會隨著距離迅速減少。一般民眾不得接近基地台天線，因為該地射頻訊號可能超過國際暴露值限制。根據最新調查顯示，在公共地區（包括學校和醫院），基地台和無線科技造成的射頻暴露值通常只有國際標準的數千分之一。

The strength of RF fields is greatest at its source, and diminishes quickly with distance. Access near base station antennas is restricted where RF signals may exceed international exposure limits. Recent surveys have indicated that RF exposures from base stations and wireless technologies in publicly accessible areas (including schools and hospitals) are normally thousands of times below international standards.

事實上，在基地台射頻訊號的暴露值與FM電台和電視一樣時，人體吸收FM電台和電視頻率（在100 MHz左右）的暴露值卻為基地台及無線科技（900 MHz及1800MHz）的5倍。這是因為FM電台和電視的頻率較低，波長較長，人體成為FM電台和電視台有效率的接收天線。再者，廣播和電視的運用已超過50年，至今沒有發現公認的健康效應。

In fact, due to their lower frequency, at similar RF exposure levels, the body absorbs up to five times more of the signal from FM radio and television than from base stations. This is because the frequencies used in FM radio (around 100 MHz) and in TV broadcasting (around 300 to 400 MHz) are lower than those employed in mobile telephony (900 MHz and 1800 MHz) and because a person's height makes the body an efficient receiving antenna. Further, radio and television broadcast stations have been in operation for the past 50 or more years without any adverse health consequence being established.

雖然大多數無線電科技都使用類比訊號，現代無線通訊技術卻使用數位傳輸。到目前為止，詳細研究並未顯示不同傳播射頻訊號調變方式會造成特定的危險性。

While most radio technologies have used analog signals, modern wireless telecommunications are using digital transmissions. Detailed reviews conducted so far have not revealed any hazard specific to different RF modulations.

癌症：媒體或部份零星報導指出，在行動電話基地台附近有多人罹患癌症，已引起大眾強烈關切。在此應予強調的是，就地理位置而言，癌症在任何人群的分佈都呈不均勻的現象。由於基地台分佈極廣，在基地台附近有多人罹患癌症很可能只是巧合。除此之外，報導的癌症患者通常罹患多種不同癌症，並無共通特性，因此基地台及無線科技不太可能癌症的共通成因。

Cancer: Media or anecdotal reports of cancer clusters around mobile phone base stations have heightened public concern. It should be noted that geographically, cancers are unevenly distributed among any population. Given the widespread presence of base stations in the environment, it is expected that possible cancer clusters will occur near base stations merely by chance. Moreover, the reported cancers in these clusters are often a collection of different types of cancer with no common characteristics and hence unlikely to have a common cause.

透過細心規劃和執行的流性病學研究，我們可以取得癌症人口分佈的科學證據。在過去15年間，學界曾發表檢討射頻發射器和癌症潛在關係的研究。這些研究並未證實，發射器產生的射頻訊號暴露值會增加罹癌風險。而長期的動物研究也未能證明暴露在射頻訊號的電磁場領域下會增加罹癌風險，甚至使用的強度遠超過基地台和無線網路所能產生的水平，亦無法證明暴露在射頻訊號的電磁場強下會增加罹癌風險。

Scientific evidence on the distribution of cancer in the population can be obtained through carefully planned and executed epidemiological studies. Over the past 15 years, studies examining a potential relationship between RF transmitters and cancer have been published. These studies have not provided evidence that RF exposure from the transmitters increases the risk of cancer. Likewise, long-term animal studies have not established an increased risk of cancer from exposure to RF fields, even at levels that are much higher than produced by base stations and wireless networks.

其他影響：很少的研究調查是針對個人暴露在基地台射頻電磁場強下，對整體健康所產生的影響。這是因為很難區分評估變數是來自於基地台微弱訊號，還是來自環境裡其他高強度射頻訊號。大多數研究都聚焦在手機使用者的射頻訊號暴露值上。人體與動物研究使受測者暴露在類似手機的射頻電磁場強下，測試腦電波、認知功能和行為，結果並未發現負面效應。和一般大眾暴露在基地台和無線網路下的射頻暴露值相比，這些研究使用的射頻暴露值要高上約1,000倍。研究並未發現影響睡眠或心血管功能的一致證據。

Other effects: Few studies have investigated general health effects in individuals exposed to RF fields from base stations. This is because of the difficulty in distinguishing possible health effects from the very low signals emitted by base stations from other higher strength RF signals in the environment. Most studies have focused on the RF exposures of mobile phone users. Human and animal studies examining brain wave patterns, cognition and behaviour after exposure to RF fields, such as those generated by mobile phones, have not identified adverse effects. RF exposures used in these studies were about 1000 times higher than those associated with general public exposure from base stations or wireless networks. No consistent evidence of altered sleep or cardiovascular function has been reported.

部分人士表示，如果他們暴露在基地台或其他電磁波裝置的射頻電磁場強下，會產生不特定的徵狀。根據WHO最近一份「電磁波超敏感症」 "Electromagnetic Hypersensitivity"概要說明書(Fact Sheet)，沒有證據顯示電磁場會導致這些徵狀。無論如何，如果有人經歷這些徵狀，我們必須承認他們的不適。

Some individuals have reported that they experience non-specific symptoms upon exposure to RF fields emitted from base stations and other EMF devices. As recognized in a recent WHO fact sheet "Electromagnetic Hypersensitivity", EMF has not been shown to cause such symptoms. Nonetheless, it is important to recognize the plight of people suffering from these symptoms.
　　
根據目前所有收集的研究證據顯示，基地台產生的射頻信號，不會對人體健康造成短或長期的負面影響。而無線網路設備所產生的射頻信號又低於基地台，可據此推論，該發現也適用於無線網路。

From all evidence accumulated so far, no adverse short- or long-term health effects have been shown to occur from the RF signals produced by base stations. Since wireless networks produce generally lower RF signals than base stations, no adverse health effects are expected from exposure to them.

防護標準Protection standards
　　
國際非游離輻射防護委員會(ICNIRP, 1998)和電機電子工程師學會(IEEE, 2005)之所以制訂國際暴露值標準，目的在於提供暴露在射頻電磁場強的有效規範，以防止已知的不良影響。

International exposure guidelines have been developed to provide protection against established effects from RF fields by the International Commission on Non-Ionizing Radiation Protection (ICNIRP, 1998) and the Institute of Electrical and Electronic Engineers (IEEE, 2005).

各國政府應採用國際標準保護公眾，避免暴露於過量的射頻訊號環境，並限制公眾接近暴露值可能超過限制的區域。

National authorities should adopt international standards to protect their citizens against adverse levels of RF fields. They should restrict access to areas where exposure limits may be exceeded.

大眾對風險的認知PUBLIC PERCEPTION OF RISK
　　
部分人士認為，射頻訊號暴露可能造成風險，甚至可能是嚴重危害。大眾恐懼的原因包括媒體宣布未經證實的科學研究，導致大眾的不確定感，以及感到可能有未知或未發現的危險。其他因素包括美感考量、缺乏對新設基地台地點的掌控或無法提供意見。經驗指出，透過教育計畫、有效溝通、公眾與其他相關人士在設立射頻發射台前參與決策過程，可提升大眾信心與接受度。

Some people perceive risks from RF exposure as likely and even possibly severe. Several reasons for public fear include media announcements of new and unconfirmed scientific studies, leading to a feeling of uncertainty and a perception that there may be unknown or undiscovered hazards. Other factors are aesthetic concerns and a feeling of a lack of control or input to the process of determining the location of new base stations. Experience shows that education programmes as well as effective communications and involvement of the public and other stakeholders at appropriate stages of the decision process before installing RF sources can enhance public confidence and acceptability.

結論CONCLUSIONS
　　
根據極低的暴露值水平以及至今收集的科學研究資料，沒有可靠的科學證據顯示，基地台和無線網路產生的微弱射頻訊號會導致不良的健康影響。

Considering the very low exposure levels and research results collected to date, there is no convincing scientific evidence that the weak RF signals from base stations and wireless networks cause adverse health effects.

世界衛生組織方案WHO Initiatives
　　
世界衛生組織透過國際電磁場專案，已建立監控電磁場科學文獻的機制，以便評估暴露在 0 到 300GHz 電磁場下對健康的影響，提供潛在電磁場危險的建議，並確認適當的防治措施。在廣泛的國際討論後，該國際電磁場專案推廣研究來以填補知識不足之處。在過去 10 年間，各國政府和研究機構也相對提供 2 億 5 千萬美元的電磁場研究資金。

WHO, through the International EMF Project, has established a programme to monitor the EMF scientific literature, to evaluate the health effects from exposure to EMF in the range from 0 to 300 GHz, to provide advice about possible EMF hazards and to identify suitable mitigation measures. Following extensive international reviews, the International EMF Project has promoted research to fill gaps in knowledge. In response national governments and research institutes have funded over $250 million on EMF research over the past 10 years.
　　
雖然並不認為暴露在基地台與其他區域無線網路射頻電磁場會對人體健康產生影響，世界衛生組織仍然推動研究更高強度的手機射頻暴露是否會對人體健康產生任何影響。

While no health effects are expected from exposure to RF fields from base stations and wireless networks, research is still being promoted by WHO to determine whether there are any health consequences from the higher RF exposures from mobile phones.
　　
WHO下屬的專業國際癌症研究機構（IARC）將於2006到2007年檢討射頻訊號電磁場的致癌風險，國際電磁波專案屆時將於2007到2008年整體評估射頻訊號電磁場強的健康風險。

The International Agency for Research on Cancer (IARC), a WHO specialized agency, is expected to conduct a review of cancer risk from RF fields in 2006-2007 and the International EMF Project will then undertake an overall health risk assessment for RF fields in 2007-2008.

參考資料FURTHER READING

ICNIRP (1998) http://www.icnirp.org/documents/emfgdl.pdf
IEEE (2006) IEEE C95.1-2005 IEEE人體射頻電磁場暴露值安全標準（3 kHz到300 GHz）（於2006年度4月出版）

IEEE (2006) IEEE C95.1-2005 "IEEE Standard for Safety Levels with Respect to Human Exposure to Radio Frequency Electromagnetic Fields, 3 kHz to 300 GHz"

相關聯結RELATED LINKS
Base stations & wireless networks: Exposures & health consequences
(http://www.who.int/peh-emf/meetings/base_stations_june05/en/index.html)

Fact sheet: Electromagnetic fields and public health: Electromagnetic Hypersensitivity
(http://www.who.int/mediacentre/factsheets/fs296/en/index.html)

WHO handbook on "Establishing a Dialogue on Risks from Electromagnetic Fields"
(http://www.who.int/peh-emf/publications/risk_hand/en/index.html)

2006 WHO Research Agenda for Radio Frequency Fields [pdf 791kb]
(http://www.who.int/peh-emf/research/rf_research_agenda_2006.pdf)
http://www.who.int/mediacentre/factsheets/fs304/en/index.html

資料出處：世界衛生組織 WHO
http://www.who.int/mediacentre/factsheets/fs304/en/index.html