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Cellular Telephone Use and Cancer Risk
Untitled Document
Key Points
- Cellular telephones emit radiofrequency (RF) energy, which is another
name for radio waves (see Questions 1 and 2).
- Exposure to high levels of RF energy can heat body tissue,
but RF energy exposures from cellular telephones are too low to cause significant tissue heating (see Question 2).
- Concerns have been raised that RF energy from cellular telephones
may pose a cancer
risk to users (see Questions 1 and 2).
- Researchers are studying tumors
of the brain and central
nervous system (CNS)
and other sites of the head and neck because cellular telephones are
held next to the head when used (see Question 5).
- Studies have not shown any consistent link between cellular telephone
use and cancer, but scientists feel that additional research is needed
before firm conclusions can be drawn (see Questions 6 and 7).
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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
and is under investigation for its effects on the human body (1).
- Cellular telephone technology is relatively new and is still 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
2007, there were more than 255 million subscribers to cellular telephone
service in the United States, according to the Cellular Telecommunications
and Internet Association (CTIA). 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 phones
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 is 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 to 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 transmissions
• how far the antenna is extended
• the size of the handset
• 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 phones 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 brain cancer, but results from long-term studies
are still limited.
Several studies have investigated the risk of developing three types of brain
tumors, namely 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 (IARC) (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 underway and will provide more comprehensive and stable risk estimates
than analyses from the individual countries.
Two reports published in November 2004 by researchers from individual countries
that are participating in the INTERPHONE study described results of assessments
of cellular telephone use and the risk of acoustic neuroma. One report described
a Danish case-control
study that showed no increased risk of acoustic neuroma in long-term (10
years or more) cellular telephone users compared with short-term users, and
there was no increase in the incidence
of tumors on the side of the head where the phone was usually held (13).
The other report described a Swedish study that examined similar populations
and found a slightly elevated risk of acoustic neuroma in long-term cellular
telephone users but not in short-term users (14).
A pooled analysis of data from Denmark, Finland, Norway, Sweden, and the
United Kingdom did not find relationships between the risk of acoustic neuroma
and the duration of cell phone use, cumulative hours of use, or number of
calls; however, the risk of a tumor on the same side of the head as the reported
phone use was higher among persons who had used a cell phone for 10 years
or more (9).
Other reports from the Danish and Swedish researchers who are collaborating
in the INTERPHONE study investigated whether a relationship exists between
cellular telephone use and the risk of meningioma or glioma. These studies
from Denmark and Sweden compared individuals with meningioma or glioma with
a control
group of disease-free individuals and found no link between these conditions
and cellular telephone use (15, 16).
Pooled analyses of data from four Nordic countries and the United Kingdom
did not show overall associations between the risk of glioma or meningioma
and the cumulative hours of cell phone use or the number of calls (17,
18). There was a slightly increased risk of glioma occurring
on the same side of the head as the reported phone use among persons who used
a cell phone for at least 10 years (17).
In an attempt to avoid the issue of biases associated with case-control studies,
investigators defined a cohort of 420,095 persons in Denmark with cellular
phone subscriptions and linked this roster with the Danish Cancer Registry
to identify brain tumors occurring in this population (7,
8). Cellular phone use was not associated with glioma, meningioma,
or acoustic neuroma, even among persons who had been subscribers for 10 or
more years. This type of prospective
study has the advantage of not having to rely on peoples’ ability to
remember past cellular phone use.
Incidence data from the Surveillance, Epidemiology
and End Results (SEER) program of the National
Cancer Institute have shown no increase between 1987 and 2005 in the age-adjusted
incidence of brain or other nervous system cancers despite the dramatic increase
in use of cellular telephones (19).
There are very few studies of the possible relationship between cell phone
use and tumors other than those of the brain and central nervous system (20–23).
- Why are the results of the studies inconsistent?
There are several reasons for the discrepancies between studies:
- Information about cellular telephone use, including the frequency of
use and the duration of calls, has largely been assessed through questionnaires.
The completeness and accuracy of the data collected during such interviews
is dependent on the memory of the responding individuals. In case-control
studies, individuals with brain tumors may remember cellular telephone use
differently from healthy individuals, which can result in a problem known
as recall bias.
- Cellular telephone use is relatively new (mostly since the 1990s), and
cellular technology continues to change (1). Although
older studies evaluated RF energy exposure from analog telephones, most
cellular telephones today use digital technology, which operates at a different
frequency and power level than analog phones.
- The interval between exposure to a carcinogen
and the clinical
onset of a tumor may be many years or decades. Scientists have been unable
to monitor large cohorts of cellular telephone users for the length of time
it might take for brain tumors to develop (1).
- Other limitations of current epidemiologic studies on cellular telephone
use and brain cancer include a lack of verifiable data regarding cumulative
RF energy exposure over time (the total amount of RF energy individuals
have encountered) and potential errors in the exposure information reported
by study participants after individuals are diagnosed
with cancer, a problem known as reporting bias (24,
25). In addition, participation rates are frequently
different between case subjects and control subjects in brain tumor studies,
a problem known as participation bias. Some studies have indicated
greater participation by individuals diagnosed with brain tumors compared
with controls, and participation rates may be related to cellular phone
use.
- The use of “hands-free” wireless technology, such as Bluetooth®,
is increasing and may contribute to variation in cellular phone exposures.
Although research has not consistently demonstrated a link between cellular
telephone use and cancer, scientists still caution that further surveillance
is needed before conclusions can be drawn about the risk of cancer from cellular
telephones (1).
- Do children have a higher risk of developing cancer due
to cellular telephone use than adults?
There are currently no data on cellular telephone use and risk in children
because no published studies to date have included children. Cellular telephone
use is increasing rapidly in children and adolescents, and they are likely
to accumulate many years of exposure during their lives (1).
In addition, children may be at greater risk because their nervous systems
are still developing at the time of exposure.
- What can cellular telephone users do to reduce their exposure
to RF energy?
The U.S. Food and Drug
Administration (FDA) has suggested some steps that cellular telephone users
can take if they are concerned about potential health risks from cellular
telephones:
- Reserve the use of cellular telephones for shorter conversations, or
for times when a conventional phone is not available.
- Switch to a type of cellular telephone with a hands-free device that
will place more distance between the antenna and the head of the phone user.
Hands-free kits reduce the amount of RF energy exposure to the head because
the antenna, which is the source of RF energy, is not placed against the head
(2). However, most studies conducted on cellular telephone
use and cancer risk have focused on hand-held models not equipped with hands-free
systems because they deliver the most RF energy to the user’s head.
- Where can I find more information about RF energy exposure?
The Federal Communications Commission (FCC), which regulates interstate and
international communications, provides consumers with information about human
exposure to RF energy from cellular telephones and other devices at http://www.fcc.gov/oet/rfsafety
on the Internet. This Web page includes information about the specific absorption
rate (SAR) of cellular telephones produced and marketed within the last 1
to 2 years. The SAR corresponds to the relative amount of RF energy absorbed
into the head of a cellular telephone user. Consumers can access this information
using the phone’s FCC ID number, which is usually located on the case
of the phone.
- What are other sources of RF energy?
The most common use of RF energy is for telecommunications (2).
In the United States, cellular telephones operate in a frequency range of
about 1,800 to 2,200 megahertz (MHz) (1). In this range,
the electromagnetic radiation produced is in the form of non-ionizing RF energy.
AM/FM radios, VHF/UHF televisions, and cordless telephones (telephones that
have a base unit connected to the telephone wiring in a house) operate at
lower radio frequencies than cellular telephones. Other sources of RF energy,
including radar, satellite stations, magnetic
resonance imaging (MRI)
devices, industrial equipment, and microwave ovens, operate at somewhat higher
radio frequencies (2).
Selected References
- Ahlbom A, Green A, Kheifets L, Savitz D, Swerdlow A. Epidemiology of health
effects on radiofrequency exposure. Environmental Health Perspectives
2004; 112(17): 1741–1754.
- Food and Drug Administration (2003). Cell Phone Facts: Consumer Information
on Wireless Phones. Retrieved August 28, 2008, from: http://www.fda.gov/cellphones.
- Inskip PD, Tarone RE, Hatch EE, et al. Cellular-telephone use and brain
tumors. New England Journal of Medicine 2001; 344(2):79–86.
- Hepworth SJ, Schoemaker MJ, Muir KR, et al. Mobile phone use and risk of
glioma in adults: Case-control study. British Medical Journal 2006;
332(7546):883–887.
- Klaeboe L, Blaasaas KG, Tynes T. Use of mobile phones in Norway and risk
of intracranial tumours. European Journal of Cancer Prevention 2007;
16(2):158–164.
- Takebayashi T, Varsier N, Kikuchi Y, et al. Mobile phone use, exposure
to radiofrequency electromagnetic field, and brain tumour: A case-control
study. British Journal of Cancer 2008; 98(3):652–659.
- Johansen C, Boice Jr. JD, McLaughlin JK, Olsen JH. Cellular telephones
and cancer: A nationwide cohort study in Denmark. Journal of the National
Cancer Institute 2001; 93(3):203–207.
- Schuz J, Jacobsen R, Olsen JH, et al. Cellular telephone use and cancer
risk: Update of a nationwide Danish cohort. Journal of the National Cancer
Institute 2006; 98(23): 1707–1713.
- Schoemaker MJ, Swerdlow AJ, Ahlbom A, et al. Mobile phone use and risk
of acoustic neuroma: Results of the Interphone case-control study in five
North European countries. British Journal of Cancer 2005; 93(7):842–848.
- Hours M, Bernard M, Montestrucq L, et al. [Cell phones and risk of brain
and acoustic nerve tumours: The French INTERPHONE case-control study.] Revue
d'Epidemiologie et de Sante Publique 2007; 55(5):321–332.
- Cardis E, Richardson L, Deltour I, et al. The INTERPHONE study: Design,
epidemiological methods, and description of the study population. European
Journal of Epidemiology 2007; 22(9):647–664.
- International Agency for Research on Cancer (2004). The INTERPHONE
Study. Lyon, France: International Agency for Research on Cancer. Retrieved
August 28, 2008, from: http://www.iarc.fr/en/Research-Groups/Clusters-Groups/Biostatistics-and-Epidemiology-Cluster/Radiation-Group/The-INTERPHONE-Study.
- Christensen HC, Schuz J, Kosteljanetz M, et al. Cellular telephone use
and risk of acoustic neuroma. American Journal of Epidemiology 2004;
159(3):277–283.
- Lonn S, Ahlbom A, Hall P, Feychting M. Mobile phone use and the risk of
acoustic neuroma. Epidemiology 2004; 15(6):653–659.
- Christensen HC, Schuz J, Kosteljanetz M, et al. Cellular telephones and
risk for brain tumors: A population-based, incident case-control study. Neurology
2005; 64(7):1189–1195.
- Lonn S, Ahlbom A, Hall P, Feychting M, Swedish Interphone Study Group.
Long-term mobile phone use and brain tumor risk. American Journal of Epidemiology
2005; 161(6):526–535.
- Lahkola A, Auvinen A, Raitanen J, et al. Mobile phone use and risk of glioma
in five North European countries. International Journal of Cancer
2007; 120(8):1769–1775.
- Lahkola A, Salminen T, Raitanen J, et al. Meningioma and mobile phone use--a
collaborative case-control study in five North European countries. International
Journal of Epidemiology 2008; August 2 [Epub ahead of print].
- Ries LAG, Melbert D, Krapcho M, et al (2007). SEER Cancer Statistics
Review, 1975-2005. Bethesda, MD: National Cancer Institute. Retrieved
August 28, 2008, from: http://seer.cancer.gov/csr/1975_2005.
- Stang A, Anastassiou G, Ahrens W, et al. The possible role of radiofrequency
radiation in the development of uveal melanoma. Epidemiology 2001;
12(1):7–12.
- Linet MS, Taggart T, Severson RK, et al. Cellular telephones and non-Hodgkin
lymphoma. International Journal of Cancer 2006; 119(10):2382–2388.
- Lonn S, Ahlbom A, Christensen HC, et al. Mobile phone use and risk of parotid
gland tumor. American Journal of Epidemiology 2006; 164(7):637–643.
- Sadetzki S, Chetrit A, Jarus-Hakak A, et al. Cellular phone use and risk
of benign and malignant parotid gland tumors--a nationwide case-control study.
American Journal of Epidemiology 2008; 167(4):457–467.
- Lahkola A, Salminen T, Auvinen A. Selection bias due to differential participation
in a case-control study of mobile phone use and brain tumors. Annals of
Epidemiology 2005; 15(5):321–325.
- Vrijheid M, Deltour I, Krewski D, Sanchez M, Cardis E. The effects of recall
errors and of selection bias in epidemiologic studies of mobile phone use
and cancer risk. Journal of Exposure Science and Environmental Epidemiology
2006; 16(4):371–384.
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Glossary Terms
acoustic (ah-KOOS-tik)
Having to do with sound or hearing.
benign (beh-NINE)
Not cancerous. Benign tumors may grow larger but do not spread to other parts of the body. Also called nonmalignant.
bias (BY-us)
In a scientific research study or clinical trial, a flaw in the study design or the method of collecting or interpreting information. Biases can lead to incorrect conclusions about what the study or clinical trial showed.
brain tumor
The growth of abnormal cells in the tissues of the brain. Brain tumors can be benign (not cancer) or malignant (cancer).
cancer (KAN-ser)
A term for
diseases in which abnormal cells divide without control and
can invade nearby tissues. Cancer cells can also spread to
other parts of the body through the blood and lymph
systems. There are several main types of cancer. Carcinoma
is a cancer that begins in the skin or in tissues that line
or cover internal organs. Sarcoma is a cancer that begins in
bone, cartilage, fat, muscle, blood vessels, or other
connective or supportive tissue. Leukemia is a cancer that
starts in blood-forming tissue such as the bone marrow, and
causes large numbers of abnormal blood cells to be produced
and enter the blood. Lymphoma and multiple myeloma are
cancers that begin in the cells of the immune system.
Central nervous system cancers are cancers that begin in
the tissues of the brain and spinal cord. Also called malignancy.
carcinogen (kar-SIN-o-jin)
Any substance that causes cancer.
case-control study (KAYS-kun-TROLE STUH-dee)
A study that compares two groups of people: those with the disease or condition under study (cases) and a very similar group of people who do not have the disease or condition (controls). Researchers study the medical and lifestyle histories of the people in each group to learn what factors may be associated with the disease or condition. For example, one group may have been exposed to a particular substance that the other was not. Also called retrospective study.
cell (sel)
The individual unit that makes up the tissues of the body. All living things are made up of one or more cells.
clinical (KLIH-nih-kul)
Having to do with the examination and treatment of patients.
control group
In a clinical trial, the group that does not receive the new treatment being studied. This group is compared to the group that receives the new treatment, to see if the new treatment works.
diagnosis (DY-ug-NOH-sis)
The process of identifying a disease, such as cancer, from its signs and symptoms.
drug
Any substance, other than food, that is used to prevent, diagnose, treat or relieve symptoms of a disease or abnormal condition. Also refers to a substance that alters mood or body function, or that can be habit-forming or addictive, especially a narcotic.
electromagnetic radiation (ee-LEK-troh-mag-NEH-tik ray-dee-AY-shun)
Low-energy radiation that comes from the interaction of electric and magnetic fields. Sources include power lines, electric appliances, radio waves, microwaves, and others. Also called electromagnetic field.
epidemiology (EH-pih-dee-mee-AH-loh-jee)
The study of the patterns, causes, and control of disease in groups of people.
glioma (glee-OH-muh)
A cancer of the brain that begins in glial cells (cells that surround and support nerve cells).
incidence
The number of new cases of a disease diagnosed each year.
ionizing radiation (I-uh-NYZ-ing RAY-dee-AY-shun)
A type of radiation made (or given off ) by x-ray procedures, radioactive substances, rays that enter the Earth's atmosphere from outer space, and other sources. At high doses, ionizing radiation increases chemical activity inside cells and can lead to health risks, including cancer.
magnetic resonance imaging (mag-NEH-tik REH-zuh-nunts IH-muh-jing)
A procedure in which radio waves and a powerful magnet linked to a computer is used to create detailed pictures of areas inside the body. These pictures can show the difference between normal and diseased tissue. Magnetic resonance imaging makes better images of organs and soft tissue than other scanning techniques, such as computed tomography (CT) or x-ray. Magnetic resonance imaging is especially useful for imaging the brain, the spine, the soft tissue of joints, and the inside of bones. Also called MRI, NMRI, and nuclear magnetic resonance imaging.
malignant (muh-LIG-nunt)
Cancerous. Malignant tumors can invade and destroy nearby tissue and spread to other parts of the body.
membrane
A very thin layer of tissue that covers a surface.
meninges (meh-NIN-jees)
The three thin layers of tissue that cover and protect the brain and spinal cord.
meningioma (meh-NIN-jee-OH-muh)
A type of slow-growing tumor that forms in the meninges (thin layers of tissue that cover and protect the brain and spinal cord). Meningiomas usually occur in adults.
MRI
A procedure in which radio waves and a powerful magnet linked to a computer is used to create detailed pictures of areas inside the body. These pictures can show the difference between normal and diseased tissue. MRI makes better images of organs and soft tissue than other scanning techniques, such as computed tomography (CT) or x-ray. MRI is especially useful for imaging the brain, the spine, the soft tissue of joints, and the inside of bones. Also called magnetic resonance imaging, NMRI, and nuclear magnetic resonance imaging.
National Cancer Institute
The National Cancer Institute, part of the National Institutes of Health of the United States Department of Health and Human Services, is the Federal Government's principal agency for cancer research. The National Cancer Institute conducts, coordinates, and funds cancer research, training, health information dissemination, and other programs with respect to the cause, diagnosis, prevention, and treatment of cancer. Access the National Cancer Institute Web site at http://www.cancer.gov. Also called NCI.
nerve
A bundle of fibers that receives and sends messages between the body and the brain. The messages are sent by chemical and electrical changes in the cells that make up the nerves.
neuroma (NOOR-oh-ma)
A tumor that arises in nerve cells.
prospective (proh-SPEK-tiv)
In medicine, a study or clinical trial in which participants are identified and then followed forward in time.
radiation (RAY-dee-AY-shun)
Energy released in the form of particle or electromagnetic waves. Common sources of radiation include radon gas, cosmic rays from outer space, medical x-rays, and energy given off by a radioisotope (unstable form of a chemical element that releases radiation as it breaks down and becomes more stable).
salivary gland (SA-lih-VAYR-ee gland)
A gland in the mouth that produces saliva.
spinal cord
A column of nerve tissue that runs from the base of the skull down the back. It is surrounded by three protective membranes, and is enclosed within the vertebrae (back bones). The spinal cord and the brain make up the central nervous system, and spinal cord nerves carry most messages between the brain and the rest of the body.
x-ray
A type of high-energy radiation. In low doses, x-rays are used to diagnose diseases by making pictures of the inside of the body. In high doses, x-rays are used to treat cancer.
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Table of Links
1 | http://www.cancer.gov/cancertopics/factsheet/Risk/magnetic-fields |
2 | http://www.cancer.gov/cancertopics/prevention-genetics-causes/causes |
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