What antennas do to your head

What antennas do to your head

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# Why is there concern that cellular telephones may cause cancer?

There are three main reasons why people are concerned that cellular telephones (also known as "wireless" or "mobile" telephones) may cause certain types of cancer:

* Cellular telephones emit radiofrequency (RF) energy (radio waves), which is a form of radiation that is under investigation for its effects on the human body (1).

* Cellular telephone technology emerged in Europe in the 1980s but did not come into widespread use in the United States until the 1990s. The technology is rapidly changing, so there are few long-term studies of the effects of RF energy from cellular telephones on the human body (1).

* The number of cellular telephone users has increased rapidly. As of December 2008, there were more than 270 million subscribers to cellular telephone service in the United States, according to the Cellular Telecommunications and Internet Association. This is an increase from 110 million users in 2000 and 208 million users in 2005.

For these reasons, it is important to learn whether RF energy from cellular telephones affects human health.
# What is RF energy and how can it affect the body?

RF energy is a form of electromagnetic radiation.

Electromagnetic radiation can be divided into two types: Ionizing (high-frequency) and non-ionizing (low-frequency) (2). RF energy is a form of non-ionizing electromagnetic radiation. Ionizing radiation, such as that produced by x-ray machines, can pose a cancer risk at high levels of exposure. However, it is not known whether the non-ionizing radiation emitted by cellular telephones is associated with cancer risk (2).

Studies suggest that the amount of RF energy produced by cellular telephones is too low to produce significant tissue heating or an increase in body temperature. However, more research is needed to determine what effects, if any, low-level non-ionizing RF energy has on the body and whether it poses a health danger (2).
# How is a cellular telephone user exposed to RF energy?

A cellular telephone's main source of RF energy is produced through its antenna. The antenna of a hand-held cellular telephone is in the handset, which is typically held against the side of the head when the telephone is in use. The closer the antenna is to the head, the greater a person's expected exposure to RF energy. The amount of RF energy absorbed by a person decreases significantly with increasing distance between the antenna and the user. The intensity of RF energy emitted by a cellular telephone depends on the level of the signal sent to or from the nearest base station (1).

When a call is placed from a cellular telephone, a signal is sent from the antenna of the phone to the nearest base station antenna. The base station routes the call through a switching center, where the call can be transferred to another cellular telephone, another base station, or the local land-line telephone system. The farther a cellular telephone is from the base station antenna, the higher the power level needed to maintain the connection. This distance determines, in part, the amount of RF energy exposure to the user.
# What determines how much RF energy a cellular telephone user experiences?

A cellular telephone user's level of exposure to RF energy depends on several factors, including:

* The number and duration of calls.
* The amount of cellular telephone traffic at a given time.
* The distance from the nearest cellular base station.
* The quality of the cellular transmission.
* The size of the handset.
* How far the antenna is extended.
* Whether or not a hands-free device is used.

# What parts of the body may be affected during cellular telephone use?

There is concern that RF energy produced by cellular phones may affect the brain and nervous system tissue in the head because hand-held cellular telephones are usually held close to the head. Researchers have focused on whether RF energy can cause malignant (cancerous) brain tumors such as gliomas (cancers of the brain that begin in glial cells, which surround and support the nerve cells), as well as benign (noncancerous) tumors, such as acoustic neuromas (tumors that arise in the cells of the nerve that supplies the ear) and meningiomas (tumors that occur in the meninges, which are the membranes that cover and protect the brain and spinal cord) (1). The salivary glands also may be exposed to RF energy from cellular telephones held close to the head.
# What studies have been done, and what do they show?

Numerous studies have investigated the relationship between cellular telephone use and the risk of developing malignant and benign brain tumors, but results from long-term studies are still limited.

Several studies have investigated the risk of developing three types of brain tumors: Glioma, meningioma, and acoustic neuroma. Results from the majority of these studies have found no association between hand-held cellular telephone use and the risk of brain cancer (3–8); however, some, but not all, long-term studies have suggested slightly increased risks for certain types of brain tumors (9, 10). Further evaluation of long-term exposures (more than 10 years) is needed.

A series of multinational case-control studies (comparing individuals who have a disease or condition [case subjects] with a similar group of people who do not have the disease or condition [control subjects]), collectively known as the INTERPHONE study, are being coordinated by the International Agency for Research on Cancer (11). The primary objective of these studies is to assess whether RF energy exposure from cellular telephones is associated with an increased risk of malignant or benign brain tumors and other head and neck tumors. Participating countries include Australia, Canada, Denmark, Finland, France, Germany, Israel, Italy, Japan, New Zealand, Norway, Sweden, and the United Kingdom (12). Several reports describing data from individual countries have been published independently by researchers involved in the INTERPHONE study; however, these reports represent only a portion of the entire INTERPHONE dataset. The combined INTERPHONE analysis is under way and will provide more comprehensive and stable risk estimates than analyses from the individual countries.

http://www.cancer.gov/cancertopics/factsheet/Risk/cellphones