公衞教學－手機和健康

領域：流行病學（含預防醫學）
題目：手機和健康
作者：何文照老師 公共衛生學系

我們每天日常生活依賴手機情形日益加重，手機是否引起健康問題也益受關注，美國疾病管制暨預防中心(US CDC-參考資料1)參考世界衛生組織 (WHO-參考資料1)等文獻，彙整提供有關重要資訊，並加註個人所學對可能致癌物質之法規值設定之簡要說明。

手機使用會致癌嗎？

目前沒有足夠科學證據可以充分提供答案回答這個問題，一些組織建議謹慎使用手機，目前需要更多的研究加以進一步探討手機使用和健康等相關議題。

使用手機會有輻射暴露嗎？

是的，手機和無線電話使用的是射頻輻射來發送信號。射頻輻射與我們已知有危害的輻射類型（如X射線）不同。我們無法確知手機的射頻輻射經過數年使用暴露後是否會導致健康相關問題。國際癌症研究機構（IARC）將射頻輻射歸類為一種“可能的人類致癌物”。

人們是否應該停止使用手機？

目前科學上無法下定論，科學研究正在進行中來確定使用手機是否會造成健康影響。同樣重要的是要考慮手機使用的好處，尤其是在必要或緊急狀況手機使用價值重大 - 甚至可以挽救生命。

如果您擔心使用手機，請您參考下面的建議。

可減少射頻輻射靠近你的身體：

1. 使用耳機或揚聲器。

2. 在過去，射頻可能干擾心律調節器的運行。如果您目前使用心律調節器且關心您手機使用如何可能會影響它，請馬上聯繫您的健康照護提供者。

進行中的研究？

科學家們正在繼續研究使用手機可能對健康的影響。例如，世界衛生組織（WHO）目前正在進行研究，探討手機使用是否可能影響：1. 某些類型的腫瘤（腫塊或增生）；2. 視覺；3. 睡眠；4. 記憶力，和5, 頭痛。

註: 可能的人類致癌物在法規值之設定原則，首先於公式分子部分，考量系統性危害之防範，再者於公式分母部分，考量不確定因子，將致癌危害調控於可接受風險範圍內。

參考資料 1, US CDC:

Frequently Asked Questions about Cell Phones and Your Health

Most of us depend on cell phones every day. Some people wonder if cell phones can cause health problems. Here’s what you should know about cell phones and your health.

Can using a cell phone cause cancer?

There is no scientific evidence that provides a definite answer to that question. Some organizations recommend caution in cell phone use. More research is needed before we know if using cell phones causes health effects.

Do cell phones give off (emit) radiation?

Yes – cell phones and cordless phones use radiofrequency radiation (RF) to send signals. RF is different from other types of radiation (like x-rays) that we know can be harmful. We don’t know for sure if RF radiation from cell phones can cause health problems years later. The International Agency for Research on Cancer (IARC) has classified RF radiation as a “possible human carcinogen.” (A carcinogen is an agent that causes cancer.)

Should people stop using cell phones?

At this time we do not have the science to link health problems to cell phone use. Scientific studies are underway to determine whether cell phone use may cause health effects. It is also important to consider the benefits of cell phones. Their use can be valuable in an urgent or emergency situation – and even save lives.

If you are worried about cell phone use, follow the tips below.

Why has the information on this page been updated?

CDC has not changed its position on health effects associated with the use of cell phones. The agency updated these cell phone FAQs in June 2014 as part of efforts to ensure that health information for the public followed best practices, including the use of plain, easy-to-understand, language. During this process, revisions were introduced which inadvertently led some visitors to the web page to believe that a change in position had occurred. The corrected FAQs are now available on this page.

CDC announces changes in public health policy and recommendations through publication in the peer-reviewed literature, usually accompanied by outreach to partners and a media announcement. We apologize for any confusion that resulted from our efforts to ensure that agency information is presented in easy-to-understand language.

Cell phone tips

To reduce radio frequency radiation near your body:

Get a hands-free headset that connects directly to your phone.

Use speaker-phone more often.

In the past, RF interfered with the operation of some pacemakers. If you have a pacemaker and are concerned about how your cell phone use may affect it, contact your health care provider.

What research is being done to learn more about cell phones and health?

Scientists are continuing to study the possible health effects of cell phone use. For example, the World Health Organization (WHO) is currently looking into how cell phones may affect:

Some types of tumors (a lump or growth)

Our eyes

Sleep

Memory

Headaches

In the News: Acoustic Neuroma

Scientists are looking into a possible link between cell phone use and certain types of tumor. One type is called an acoustic neuroma (“ah-COOS-tik nur-OH-ma”). This type of tumor grows on the nerve that connects the ear to the brain. It doesn’t cause cancer, but it may lead to other health problems, like hearing loss. Another type scientists are looking into is called a glioma (“glee-OH-ma”). This is a tumor found in the brain or central nervous system of the body.

(Page last reviewed: June 9, 2014, Page last updated: June 9, 2014

Content source: Centers for Disease Control and Prevention)

參考資料 2, WHO:

Electromagnetic fields and public health: mobile phones

Fact sheet N°193

Reviewed October 2014

Key facts

Mobile phone use is ubiquitous with an estimated 6.9 billion subscriptions globally.

The electromagnetic fields produced by mobile phones are classified by the International Agency for Research on Cancer as possibly carcinogenic to humans.

Studies are ongoing to more fully assess potential long-term effects of mobile phone use.

WHO will conduct a formal risk assessment of all studied health outcomes from radiofrequency fields exposure by 2016.

Mobile or cellular phones are now an integral part of modern telecommunications. In many countries, over half the population use mobile phones and the market is growing rapidly. In 2014, there is an estimated 6.9 billion subscriptions globally. In some parts of the world, mobile phones are the most reliable or the only phones available.

Given the large number of mobile phone users, it is important to investigate, understand and monitor any potential public health impact.

Mobile phones communicate by transmitting radio waves through a network of fixed antennas called base stations. Radiofrequency waves are electromagnetic fields, and unlike ionizing radiation such as X-rays or gamma rays, can neither break chemical bonds nor cause ionization in the human body.

Exposure levels

Mobile phones are low-powered radiofrequency transmitters, operating at frequencies between 450 and 2700 MHz with peak powers in the range of 0.1 to 2 watts. The handset only transmits power when it is turned on. The power (and hence the radiofrequency exposure to a user) falls off rapidly with increasing distance from the handset. A person using a mobile phone 30–40 cm away from their body – for example when text messaging, accessing the Internet, or using a “hands free” device – will therefore have a much lower exposure to radiofrequency fields than someone holding the handset against their head.

In addition to using "hands-free" devices, which keep mobile phones away from the head and body during phone calls, exposure is also reduced by limiting the number and length of calls. Using the phone in areas of good reception also decreases exposure as it allows the phone to transmit at reduced power. The use of commercial devices for reducing radiofrequency field exposure has not been shown to be effective.

Mobile phones are often prohibited in hospitals and on airplanes, as the radiofrequency signals may interfere with certain electro-medical devices and navigation systems.

Are there any health effects?

A large number of studies have been performed over the last two decades to assess whether mobile phones pose a potential health risk. To date, no adverse health effects have been established as being caused by mobile phone use.

Short-term effects

Tissue heating is the principal mechanism of interaction between radiofrequency energy and the human body. At the frequencies used by mobile phones, most of the energy is absorbed by the skin and other superficial tissues, resulting in negligible temperature rise in the brain or any other organs of the body.

A number of studies have investigated the effects of radiofrequency fields on brain electrical activity, cognitive function, sleep, heart rate and blood pressure in volunteers. To date, research does not suggest any consistent evidence of adverse health effects from exposure to radiofrequency fields at levels below those that cause tissue heating. Further, research has not been able to provide support for a causal relationship between exposure to electromagnetic fields and self-reported symptoms, or “electromagnetic hypersensitivity”.

Long-term effects

Epidemiological research examining potential long-term risks from radiofrequency exposure has mostly looked for an association between brain tumours and mobile phone use. However, because many cancers are not detectable until many years after the interactions that led to the tumour, and since mobile phones were not widely used until the early 1990s, epidemiological studies at present can only assess those cancers that become evident within shorter time periods. However, results of animal studies consistently show no increased cancer risk for long-term exposure to radiofrequency fields.

Several large multinational epidemiological studies have been completed or are ongoing, including case-control studies and prospective cohort studies examining a number of health endpoints in adults. The largest retrospective case-control study to date on adults, Interphone, coordinated by the International Agency for Research on Cancer (IARC), was designed to determine whether there are links between use of mobile phones and head and neck cancers in adults.

The international pooled analysis of data gathered from 13 participating countries found no increased risk of glioma or meningioma with mobile phone use of more than 10 years. There are some indications of an increased risk of glioma for those who reported the highest 10% of cumulative hours of cell phone use, although there was no consistent trend of increasing risk with greater duration of use. The researchers concluded that biases and errors limit the strength of these conclusions and prevent a causal interpretation.

Based largely on these data, IARC has classified radiofrequency electromagnetic fields as possibly carcinogenic to humans (Group 2B), a category used when a causal association is considered credible, but when chance, bias or confounding cannot be ruled out with reasonable confidence.

While an increased risk of brain tumors is not established, the increasing use of mobile phones and the lack of data for mobile phone use over time periods longer than 15 years warrant further research of mobile phone use and brain cancer risk. In particular, with the recent popularity of mobile phone use among younger people, and therefore a potentially longer lifetime of exposure, WHO has promoted further research on this group. Several studies investigating potential health effects in children and adolescents are underway.

Exposure limit guidelines

Radiofrequency exposure limits for mobile phone users are given in terms of Specific Absorption Rate (SAR) – the rate of radiofrequency energy absorption per unit mass of the body. Currently, two international bodies 1, 2 have developed exposure guidelines for workers and for the general public, except patients undergoing medical diagnosis or treatment. These guidelines are based on a detailed assessment of the available scientific evidence.

WHO'S response

In response to public and governmental concern, WHO established the International Electromagnetic Fields (EMF) Project in 1996 to assess the scientific evidence of possible adverse health effects from electromagnetic fields. WHO will conduct a formal risk assessment of all studied health outcomes from radiofrequency fields exposure by 2016. In addition, and as noted above, the International Agency for Research on Cancer (IARC), a WHO specialized agency, has reviewed the carcinogenic potential of radiofrequency fields, as from mobile phones in May 2011.

WHO also identifies and promotes research priorities for radiofrequency fields and health to fill gaps in knowledge through its research agendas.

WHO develops public information materials and promotes dialogue among scientists, governments, industry and the public to raise the level of understanding about potential adverse health risks of mobile phones.

Reference:

1 International Commission on Non-Ionizing Radiation Protection (ICNIRP). Statement on the "Guidelines for limiting exposure to time-varying electric, magnetic and electromagetic fields (up to 300 GHz)", 2009.

2 Institute of Electrical and Electronics Engineers (IEEE). IEEE standard for safety levels with respect to human exposure to radio frequency electromagnetic fields, 3 kHz to 300 GHz, IEEE Std C95.1, 2005.