3.72

8/16/11

Page 1

Cell Phones and Cancer Risk

Key Points

• Cell phones emit radiofrequency energy, a form of non-ionizing electromagnetic 

radiation, which can be absorbed by tissues closest to where the phone is held.

• The amount of radiofrequency energy a cell phone user is exposed to depends on the 

technology of the phone, the distance between the phone’s antenna and the user, the

extent and type of use, and the user’s distance from cell phone towers.

• Studies thus far have not shown a consistent link between cell phone use and cancers 

of the brain, nerves, or other tissues of the head or neck. More research is needed 

because cell phone technology and how people use cell phones have been changing

rapidly.

1. Why is there concern that cell phones may cause cancer or other health problems? 

There are three main reasons why people are concerned that cell phones (also known as “wireless” or 

“mobile” telephones) might have the potential to cause certain types of cancer or other health 

problems:

• Cell phones emit radiofrequency energy (radio waves), a form of non-ionizing radiation. Tissues 

nearest to where the phone is held can absorb this energy. 

• The number of cell phone users has increased rapidly. As of 2010, there were more than 

303 million subscribers to cell phone service in the United States, according to the Cellular 

Telecommunications and Internet Association. This is a nearly threefold increase from the 110 

million users in 2000. Globally, the number of cell phone subscriptions is estimated by the 

International Telecommunications Union to be 5 billion.

• Over time, the number of cell phone calls per day, the length of each call, and the amount of time 

people use cell phones have increased. Cell phone technology has also undergone substantial 

changes. 

2. What is radiofrequency energy and how does it affect the body?

Radiofrequency energy is a form of electromagnetic radiation. Electromagnetic radiation can be 

categorized into two types: ionizing (e.g., x-rays, radon, and cosmic rays) and non-ionizing (e.g., 

radiofrequency and extremely low-frequency or power frequency) (1). 

Exposure to ionizing radiation, such as from radiation therapy, is known to increase the risk of cancer. 

However, although many studies have examined the potential health effects of non-ionizing radiation 

from radar, microwave ovens, and other sources, there is currently no consistent evidence that 

non-ionizing radiation increases cancer risk (1). 

The only known biological effect of radiofrequency energy is heating. The ability of microwave ovens 

to heat food is one example of this effect of radiofrequency energy. Radiofrequency exposure from cell 

phone use does cause heating; however, it is not sufficient to measurably increase body temperature. 

A recent study showed that when people used a cell phone for 50 minutes, brain tissues on the same 

side of the head as the phone’s antenna metabolized more glucose than did tissues on the opposite 
3.72

8/16/11

Page 2

side of the brain (2). The researchers noted that the results are preliminary, and possible health outcomes 

from this increase in glucose metabolism are still unknown.

3. How is radiofrequency energy exposure measured in epidemiologic studies? 

Levels of radiofrequency exposure are indirectly estimated using information from interviews or 

questionnaires. These measures include the following: 

• How “regularly” study participants use cell phones (the minimum number of calls per week or month) 

• The age and the year when study participants first used a cell phone and the age and the year of last use

(allows calculation of the duration of use and time since the start of use)

• The average number of cell phone calls per day, week, or month (frequency)

• The average length of a typical cell phone call

• The total hours of lifetime use, calculated from the length of typical call times, the frequency of use, and 

the duration of use 

4. What has research shown about the possible cancer-causing effects of radiofrequency energy?

Although there have been some concerns that radiofrequency energy from cell phones held closely to the head 

may affect the brain and other tissues, to date there is no evidence from studies of cells, animals, or humans 

that radiofrequency energy can cause cancer. 

It is generally accepted that damage to DNA is necessary for cancer to develop. However, radiofrequency 

energy, unlike ionizing radiation, does not cause DNA damage in cells, and it has not been found to cause 

cancer in animals or to enhance the cancer-causing effects of known chemical carcinogens in animals (3–5). 

Researchers have carried out several types of epidemiologic studies to investigate the possibility of a 

relationship between cell phone use and the risk of malignant (cancerous) brain tumors, such as gliomas, as 

well as benign (noncancerous) tumors, such as acoustic neuromas (tumors in the cells of the nerve 

responsible for hearing), most meningiomas (tumors in the meninges, membranes that cover and protect the 

brain and spinal cord), and parotid gland tumors (tumors in the salivary glands) (6). 

In one type of study, called a case-control study, cell phone use is compared between people with these types 

of tumors and people without them. In another type of study, called a cohort study, a large group of people is 

followed over time and the rate of these tumors in people who did and didn’t use cell phones is compared. 

Cancer incidence data can also be analyzed over time to see if the rates of cancer changed in large 

populations during the time that cell phone use increased dramatically. The results of these studies have 

generally not provided clear evidence of a relationship between cell phone use and cancer, but there have 

been some statistically significant findings in certain subgroups of people. 

Findings from specific research studies are summarized below:

• The Interphone Study, conducted by a consortium of researchers from 13 countries, is the largest 

health-related case-control study of use of cell phones and head and neck tumors. Most published 

analyses from this study have shown no statistically significant increases in brain or central nervous 

system cancers related to higher amounts of cell phone use. One recent analysis showed a statistically 

significant, albeit modest, increase in the risk of glioma among the small proportion of study participants 

who spent the most total time on cell phone calls. However, the researchers considered this finding 

inconclusive because they felt that the amount of use reported by some respondents was unlikely and 

because the participants who reported lower levels of use appeared to have a reduced risk of brain cancer 

(7–9). Another recent study from the group found no relationship between brain tumor locations and 

regions of the brain that were exposed to the highest level of radiofrequency energy from cell phones 

(10).

• A cohort study in Denmark linked billing information from more than 420,000 cell phone subscribers with 

brain tumor incidence data from the Danish Cancer Registry. The analyses found no association between 

cell phone use and the incidence of glioma, meningioma, or acoustic neuroma, even among people who 

had been cell phone subscribers for 10 or more years (11, 12).

• Early case-control studies in the United States, Europe, and Japan were unable to demonstrate a 

relationship between cell phone use and glioma or meningioma (13). 
3.72

8/16/11

Page 3

• Some case-control studies in Sweden found statistically significant trends of increasing brain cancer risk 

for the total amount of cell phone use and the years of use among people who began using cell phones 

before age 20 (14). However, another large, case-control study in Sweden did not find an increased risk of 

brain cancer among people between the ages of 20 and 69 (15). In addition, the international CEFALO 

study, which compared children who were diagnosed with brain cancer between ages 7 and 19 with similar 

children who were not, found no relationship between their cell phone use and risk for brain cancer (16).

• The National Cancer Institute’s (NCI) Surveillance, Epidemiology, and End Results (SEER) Program, which 

tracks cancer incidence in the United States over time, found no increase in the incidence of brain or other 

central nervous system cancers between 1987 and 2007, despite the dramatic increase in cell phone use 

in this country during that time (17). Similarly, incidence data from Denmark, Finland, Norway, and 

Sweden for the period 1974–2003 revealed no increase in age-adjusted incidence of brain tumors (18).

• Studies of workers exposed to radiofrequency energy have shown no evidence of increased risk of brain 

tumors among U.S. Navy electronics technicians, aviation technicians, or fire control technicians, those 

working in an electromagnetic pulse test program, plastic-ware workers, cellular phone manufacturing 

workers, or Navy personnel with a high probability of exposure to radar (6).

5. Why are the findings from different studies of cell phone use and cancer risk inconsistent?

A limited number of studies have shown some evidence of statistical association of cell phone use and brain 

tumor risks, but most studies have found no association. Reasons for these discrepancies include the 

following:

• Recall bias, which may happen when a study collects data about prior habits and exposures using 

questionnaires administered after disease has been diagnosed in some of the study participants. It is 

possible that study participants who have brain tumors may remember their cell phone use differently 

than individuals without brain tumors. Many epidemiologic studies of cell phone use and brain cancer risk 

lack verifiable data about the total amount of cell phone use over time. In addition, people who develop a 

brain tumor may have a tendency to recall using their cell phone mostly on the same side of their head 

where the tumor was found, regardless of whether they actually used their phone on that side of their 

head a lot or only a little.

• Inaccurate reporting, which may happen when people say that something has happened more or less

often than it actually did. People may not remember how much they used cell phones in a given time 

period. 

• Morbidity and mortality among study participants who have brain cancer. Gliomas are particularly 

difficult to study, for example, because of their high death rate and the short survival of people who 

develop these tumors. Patients who survive initial treatment are often impaired, which may affect their 

responses to questions. Furthermore, for people who have died, next-of-kin are often less familiar with 

the cell phone use patterns of their deceased family member and may not accurately describe their 

patterns of use to an interviewer. 

• Participation bias, which can happen when people who are diagnosed with brain tumors are more likely 

than healthy people (known as controls) to enroll in a research study. Also, controls who did not or rarely 

used cell phones were less likely to participate in the Interphone study than controls who used cell phones 

regularly. For example, the Interphone study reported participation rates of 78 percent for meningioma 

patients (range 56–92 percent for the individual studies), 64 percent for the glioma patients (range 

36–92 percent), and 53 percent for control subjects (range 42–74 percent) (9). One series of Swedish 

studies reported participation rates of 85 percent in people with brain cancer and 84 percent in control 

subjects (14).

• Changing technology and methods of use. Older studies evaluated radiofrequency energy exposure 

from analog cell phones. However, most cell phones today use digital technology, which operates at a 

different frequency and a lower power level than analog phones. Digital cell phones have been in use for 

more than a decade in the United States, and cellular technology continues to change (6). Texting, for 

example, has become a popular way of using a cell phone to communicate that does not require bringing 

the phone close to the head. Furthermore, the use of hands-free technology, such as wired and wireless 

headsets, is increasing and may decrease radiofrequency energy exposure to the head and brain. 
3.72

8/16/11

Page 4

6. What do expert organizations conclude?

The International Agency for Research on Cancer (IARC)

(http://www.iarc.fr/en/media-centre/pr/2011/pdfs/pr208_E.pdf), a component of the World Health 

Organization, has recently classified radiofrequency fields as “possibly carcinogenic to humans,” based on 

limited evidence from human studies, limited evidence from studies of radiofrequency energy and cancer in 

rodents, and weak mechanistic evidence (from studies of genotoxicity, effects on immune system function, 

gene and protein expression, cell signaling, oxidative stress, and apoptosis, along with studies of the possible 

effects of radiofrequency energy on the blood-brain barrier). 

The American Cancer Society (ACS) (http://pressroom.cancer.org/index.php?s=43&item=312) states that the 

IARC classification means that there could be some risk associated with cancer, but the evidence is not strong 

enough to be considered causal and needs to be investigated further. Individuals who are concerned about 

radiofrequency exposure can limit their exposure, including using an ear piece and limiting cell phone use, 

particularly among children.

The National Institute of Environmental Health Sciences (NIEHS)

(http://www.niehs.nih.gov/health/topics/agents/cellphones/index.cfm) states that the weight of the current 

scientific evidence has not conclusively linked cell phone use with any adverse health problems, but more 

research is needed. 

The U.S. Food and Drug Administration (FDA) (http://www.fda.gov/RadiationEmittingProducts/RadiationEmittingProductsandProcedures/HomeBusinessandEntertainment/CellPhones/defaul

t.htm), which is responsible for regulating the safety of machines and devices that emit radiation (including 

cell phones), notes that studies reporting biological changes associated with radiofrequency energy have failed 

to be replicated and that the majority of human epidemiologic studies have failed to show a relationship 

between exposure to radiofrequency energy from cell phones and health problems. 

The U.S. Centers for Disease Control and Prevention (CDC) 

(http://www.cdc.gov/nceh/radiation/cell_phones._FAQ.html) states that, although some studies have raised 

concerns about the possible risks of cell phone use, scientific research as a whole does not support a 

statistically significant association between cell phone use and health effects. 

The Federal Communications Commission (FCC) (http://www.fcc.gov/topic/wireless) concludes that there is 

no scientific evidence that wireless phone use can lead to cancer or to other health problems, including 

headaches, dizziness, or memory loss.

7. What studies are under way that will help further our understanding of the health effects of cell 

phone use?

A large prospective cohort study of cell phone use and its possible long-term health effects was launched in 

Europe in March 2010. This study, known as COSMOS, will enroll approximately 250,000 cell phone users 

ages 18 or older and will follow them for 20 to 30 years. 

Participants in COSMOS will complete a questionnaire about their health, lifestyle, and current and past cell 

phone use. This information will be supplemented with information from health records and cell phone 

records. More information about the COSMOS study is available at http://www.ukcosmos.org/index.html.

Another case-control study, called Mobi-Kids, is under way to examine health effects among children. More 

information about the Mobi-Kids study is available at http://www.mbkds.com. 

The challenge of such ambitious studies is to maintain the completeness of their cohorts over many decades. 

Researchers will need to determine whether participants who leave are somehow different from those who 

remain throughout the follow-up period. 

Although recall bias is minimized in studies that link to cell phone records, such studies face other problems. 

For example, it is impossible to know who is using the listed cell phone or whether that individual also places 

calls using other cell phones. To a lesser extent, it is not clear whether multiple users of a single phone will be 

represented on a single bill.
3.72

8/16/11

Page 5

The NIEHS, which is part of the National Institutes of Health, is carrying out a study of risks related to 

exposure to radiofrequency energy (the type used in cell phones) in highly specialized labs that can specify 

and control sources of radiation and measure their effects on rodents.

8. Do children have a higher risk of developing cancer due to cell phone use than adults?

In theory, children have the potential to be at greater risk than adults for developing brain cancer from cell 

phones. Their nervous systems are still developing and therefore more vulnerable to factors that may cause 

cancer. Their heads are smaller than those of adults and therefore have a greater proportional exposure to the 

field of radiofrequency radiation that is emitted by cell phones. And children have the potential of 

accumulating more years of cell phone exposure than adults do. 

So far, the data from clinical studies in children do not support this theory. The first published analysis came 

from a large case-control study called CEFALO, which was conducted in Denmark, Sweden, Norway, and 

Switzerland. The study included children who were diagnosed with brain tumors between 2004 and 2008, 

when their ages ranged from 7 to 19. Researchers did not find an association between cell phone use and 

brain tumor risk in this group of children. However, they noted that their results did not rule out the possibility 

of a slight increase in brain cancer risk among children who use cell phones, and that data gathered through 

prospective studies and objective measurements, rather than participant surveys and recollections, will be key 

in clarifying whether there is an increased risk (16).

Researchers from the Centre for Research in Environmental Epidemiology in Spain are conducting another 

international study—Mobi-Kids—to evaluate the risk associated with new communications technologies 

(including cell phones) and other environmental factors in young people ages 10 to 24. More information 

about the Mobi-Kids study is available at http://www.mbkds.com.

9. What can cell phone users do to reduce their exposure to radiofrequency energy?

The FDA and FCC have suggested some steps that concerned cell phone users can take to reduce their 

exposure to radiofrequency energy (1, 19):

• Reserve the use of cell phones for shorter conversations or for times when a landline phone is not 

available. 

• Use a hands-free device, which places more distance between the phone and the head of the user. 

Hands-free kits reduce the amount of radiofrequency energy exposure to the head because the antenna, 

which is the source of energy, is not placed against the head. 

10. Where can I find more information about radiofrequency energy from my cell phone?

The FCC provides information about the specific absorption rate (SAR) of cell phones produced and marketed 

within the last 1 to 2 years. The SAR corresponds with the relative amount of radiofrequency energy absorbed 

by the head of a cell phone user (20). Consumers can access this information using the phone’s FCC ID 

number, which is usually located on the case of the phone, and the FCC’s ID search form, which is located at

http://www.fcc.gov/oet/ea/fccid/.

11. What are other sources of radiofrequency energy?

The most common exposures to radiofrequency energy are from telecommunications devices and equipment

(1). In the United States, cell phones currently operate in a frequency range of about 1,800 to 2,200 

megahertz (MHz) (6). In this range, the electromagnetic radiation produced is in the form of 

non-ionizing radiofrequency energy. 

Cordless phones (phones that have a base unit connected to the telephone wiring in a house) often operate at 

radio frequencies similar to those of cell phones; however, since cordless phones have a limited range and 

require a nearby base, their signals are generally much less powerful than those of cell phones. 

Among other radiofrequency energy sources, AM/FM radios and VHF/UHF televisions operate at lower radio 

frequencies than cell phones, whereas sources such as radar, satellite stations, magnetic resonance imaging 

(MRI) devices, industrial equipment, and microwave ovens operate at somewhat higher radio frequencies (1).
3.72

8/16/11

Page 6

12. How common is brain cancer? Has the incidence of brain cancer changed over time?

Brain cancer incidence and mortality (death) rates have changed little in the past decade. In the United 

States, 22,340 new diagnoses and 13,110 deaths from brain cancer are estimated for 2011.

The 5-year relative survival for brain cancers diagnosed from 2001 through 2007 was 34.8 percent (21). This 

is the percentage of people diagnosed with brain cancer who will still be alive 5 years after diagnosis 

compared with the survival of a person of the same age and sex who does not have cancer.

The risk of developing brain cancer increases with age. From 2000 through 2008, there were fewer than 

5 brain cancer cases for every 100,000 people in the United States under age 65, compared with 

approximately 19 cases for every 100,000 people in the United States who were ages 65 or older (21).

Selected References 

1. Volkow ND, Tomasi D, Wang GJ, et al. Effects of cell phone radiofrequency signal exposure on brain glucose 

metabolism. JAMA 2011; 305(8):808–813. [PubMed Abstract]

2. U.S. Food and Drug Administration (2009). Radiation-Emitting Products: Reducing Exposure: Hands-free Kits 

and Other Accessories. Silver Spring, MD. Retrieved August 12, 2011, from: http://www.fda.gov/RadiationEmittingProducts/RadiationEmittingProductsandProcedures/HomeBusinessandEntertainment/CellPhones/ucm1

16293.htm

3. Hirose H, Suhara T, Kaji N, et al. Mobile phone base station radiation does not affect neoplastic transformation 

in BALB/3T3 cells. Bioelectromagnetics 2008; 29(1):55–64. [PubMed Abstract]

4. Oberto G, Rolfo K, Carbonatto M, et al. Carcinogenicity study of 217 Hz pulsed electromagnetic fields in Pim1 

transgenic mice. Radiation Research 2007; 168(3):316–326. [PubMed Abstract]

5. Zook BC, Simmens SJ. The effects of pulsed 860 MHz radiofrequency radiation on the promotion of neurogenic 

tumors in rats. Radiation Research 2006; 165(5):608–615. [PubMed Abstract]

6. Ahlbom A, Green A, Kheifets L, et al. Epidemiology of health effects on radiofrequency exposure. 

Environmental Health Perspectives 2004; 112(17):1741–1754. [PubMed Abstract]

7. 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.

[PubMed Abstract]

8. International Agency for Research on Cancer (2008). INTERPHONE Study: latest results update—8 October 

2008. Lyon, France. Retrieved August 12, 2011, from: 

http://www.iarc.fr/en/research-groups/RAD/Interphone8oct08.pdf. 

9. The INTERPHONE Study Group. Brain tumour risk in relation to mobile telephone use: results of the 

INTERPHONE international case-control study. International Journal of Epidemiology 2010; 39(3):675–694.

[PubMed Abstract]

10. Larjavaara S, Schüz J, Swerdlow A, et al. Location of gliomas in relation to mobile telephone use: a case-case 

and case-specular analysis. American Journal of Epidemiology 2011; 174(1):2–11. [PubMed Abstract]

11. 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. [PubMed Abstract]

12. Schüz 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. [PubMed Abstract]

13. Muscat JE, Malkin MG, Thompson S, et al. Handheld cellular telephone use and risk of brain cancer. JAMA

2000; 284(23):3001–3007. [PubMed Abstract]
3.72

8/16/11

Page 7

14. Hardell L, Carlberg M, Hansson Mild K. Pooled analysis of case-control studies on malignant brain tumours and 

the use of mobile and cordless phones including living and deceased subjects. International Journal of 

Oncology 2011; 38(5):1465–1474. [PubMed Abstract]

15. Lonn S, Ahlbom A, Hall P, Feychting M. Long-term mobile phone use and brain tumor risk. American Journal of 

Epidemiology 2005; 161(6):526–535. [PubMed Abstract]

16. Aydin D, Feychting M, Schüz J, et al. Mobile phone use and brain tumors in children and adolescents: a 

multicenter case-control study. Journal of the National Cancer Institute 2011; 103:1–13. [PubMed Abstract]

17. Inskip PD, Hoover RN, Devesa SS. Brain cancer incidence trends in relation to cellular telephone use in the 

United States. Neuro-Oncology 2010; 12(11):1147–1151. [PubMed Abstract]

18. Deltour I, Johansen C, Auvinen A, et al. Time trends in brain tumor incidence rates in Denmark, Finland, 

Norway, and Sweden, 1974–2003. Journal of the National Cancer Institute 2009; 101(24):1721–1724.

[PubMed Abstract]

19. U.S. Federal Communications Commission (2010). Wireless. Washington, D.C. Retrieved August 12, 2011, 

from: http://www.fcc.gov/topic/wireless.

20. U.S. Federal Communications Commission. (n.d.). FCC Encyclopedia: Specific Absorption Rate (SAR) for 

Cellular Telephones. Retrieved August 12, 2011, from: http://www.fcc.gov/encyclopedia/specific-absorptionrate-sar-cellular-telephones. 

21. Howlader N, Noone AM, Krapcho M, et al. (2011). SEER Cancer Statistics Review, 1975–2008. Bethesda, MD:

National Cancer Institute. Retrieved August 12, 2011, from: http://seer.cancer.gov/csr/1975_2008/.

# # #

Related NCI materials and Web pages:

• Magnetic Field Exposure and Cancer Fact Sheet

(http://www.cancer.gov/cancertopics/factsheet/Risk/magnetic-fields)

• Cancer Causes and Risk Factors Home Page

(http://www.cancer.gov/cancertopics/causes)

How can we help?

We offer comprehensive research-based information for patients and their families, health professionals, cancer 

researchers, advocates, and the public.

• Call NCI’s Cancer Information Service at 1–800–4–CANCER (1–800–422–6237)

• Visit us at http://www.cancer.gov or http://www.cancer.gov/espanol

• Chat using LiveHelp, NCI’s instant messaging service, at http://www.cancer.gov/livehelp

• E-mail us at cancergovstaff@mail.nih.gov

• Order publications at http://www.cancer.gov/publications or by calling 1–800–4–CANCER

• Get help with quitting smoking at 1–877–44U–QUIT (1–877–448–7848)

This fact sheet was reviewed on 8/16/11