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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 “mobile” or “wireless” telephones) might have the potential to cause certain types of cancer or other health problems:
The NCI fact sheet Electromagnetic Fields and Cancer includes information on wireless local area networks (commonly known as Wi-Fi), cell phone base stations, and cordless telephones.
What is radiofrequency energy and how does it affect the body?
Radiofrequency energy is a form of electromagnetic radiation
The energy of electromagnetic radiation is determined by its frequency; ionizing radiation is high frequency, and therefore high energy, whereas non-ionizing radiation is low frequency, and therefore low energy. The NCI fact sheet Electromagnetic Fields and Cancer lists sources of radiofrequency energy. More information about ionizing radiation can be found on the Radiation page.
The frequency of radiofrequency electromagnetic radiation ranges from 30 kilohertz (30 kHz, or 30,000 Hz) to 300 gigahertz (300 GHz, or 300 billion Hz). Electromagnetic fields in the radiofrequency range are used for telecommunications applications, including cell phones, televisions, and radio transmissions. The human body absorbs energy from devices that emit radiofrequency electromagnetic radiation. The dose of the absorbed energy is estimated using a measure called the specific absorption rate (SAR), which is expressed in watts per kilogram of body weight.
Exposure to ionizing radiation, such as from x-rays, 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, cell phones, and other sources, there is currently no consistent evidence that non-ionizing radiation increases cancer risk (1
The only consistently recognized 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 to the area of the body where a cell phone or other device is held (ear, head, etc.). However, it is not sufficient to measurably increase body temperature, and there are no other clearly established effects on the body from radiofrequency energy.
It has been suggested that radiofrequency energy might affect glucose metabolism, but two small studies that examined brain glucose metabolism after use of a cell phone showed inconsistent results. Whereas one study showed increased glucose metabolism in the region of the brain close to the antenna compared with tissues on the opposite side of the brain (2), the other study (3
Another study investigated whether exposure to the radiofrequency energy from cell phones affects the flow of blood in the brain and found no evidence of such an effect (4
The authors of these studies noted that the results are preliminary and that possible health outcomes from changes in glucose metabolism are still unknown. Such inconsistent findings are not uncommon in experimental studies of the biological effects of radiofrequency electromagnetic radiation (5
How is radiofrequency energy exposure measured in epidemiologic studies?
Epidemiologic studies use information from several sources, including questionnaires and data from cell phone service providers. Direct measurements are not yet possible outside of a laboratory setting. Estimates take into account the following:
What has research shown about the possible cancer-causing effects of radiofrequency energy?
Radiofrequency energy, unlike ionizing radiation6–8 studies in rodents of exposure to radiofrequency energy (the type used in cell phones). This investigation was conducted in highly specialized labs that can specify and control sources of radiation and measure their effects.
In February 2018, two draft technical reports summarizing the findings were made available in advance of the formal peer-review process in March 2018. Peer review is a critical component of the scientific process to ensure that research findings are meaningful, accurate, and appropriately interpreted.
NCI awaits the final peer-reviewed reports from the NTP so that they may be considered for summary inclusion in this fact sheet, along with the existing body of peer-reviewed evidence from human and animal studies. The U.S. Food and Drug Administration (FDA) issued a statement on the NTP reports stating they “believe the current safety limits for cell phones are acceptable for protecting the public health.” FDA and the Federal Communications Commission share responsibility for regulating cell phone technologies and FDA originally nominated this topic for study by NTP.
Researchers have carried out several types of epidemiologic studies in humans 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) (9
In one type of study, called a case-control study cohort study 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. These studies have not shown clear evidence of a relationship between cell phone use and cancer. However, researchers have reported some statistically significant associations for certain subgroups of people.
Three large epidemiologic studies have examined the possible association between cell phone use and cancer: Interphone, a case-control study; the Danish Study, a cohort study; and the Million Women Study, another cohort study.
Interphone
How the study was done: This is the largest health-related case-control study of cell phone use and the risk of head and neck tumors. It was conducted by a consortium of researchers from 13 countries. The data came from questionnaires that were completed by study participants.
What the study showed: 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 analysis showed a statistically significant, although 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 slightly reduced risk of brain cancer compared with people who did not use cell phones regularly (5,10,1112
Danish Study
How the study was done: This cohort study, conducted in Denmark, linked billing information from more than 358,000 cell phone subscribers with brain tumor incidence data from the Danish Cancer Registry.
What the study showed: No association was observed between cell phone use and the incidence of glioma, meningioma, or acoustic neuroma, even among people who had been cell phone subscribers for 13 or more years (13–15
Million Women Study
How the study was done: This prospective cohort study conducted in the United Kingdom used data obtained from questionnaires that were completed by study participants.
What the study showed: Self-reported cell phone use was not associated with an increased risk of glioma, meningioma, or non-central nervous system tumors. Although the original published findings reported an association with an increased risk of acoustic neuroma (1617
In addition to these three large studies, other, smaller epidemiologic studies have looked for associations between cell phone use and cancer. These include:
Investigators have also conducted analyses of incidence trends to determine whether the incidence of brain or other cancers has changed during the time that cell phone use increased dramatically. These include:
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:
What do expert organizations conclude about the cancer risk from cell phone use?
In 2011, the International Agency for Research on CancerExit Disclaimer (IARC), a component of the World Health Organization5
The Working Group indicated that, although the human studies were susceptible to bias, the findings could not be dismissed as reflecting bias alone, and that a causal interpretation could not be excluded. The Working Group noted that any interpretation of the evidence should also consider that the observed associations could reflect chance, bias, or confounding rather than an underlying causal effect. In addition, the Working Group stated that the investigation of risk of cancer of the brain associated with cell phone use poses complex methodologic challenges in the conduct of the research and in the analysis and interpretation of findings.
The American Cancer SocietyExit Disclaimer (ACS) states that the IARC classification means that there could be some cancer risk associated with radiofrequency energy, but the evidence is not strong enough to be considered causal and needs to be investigated further. Individuals who are concerned about radiofrequency energy 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) 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) 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) states that no scientific evidence definitively answers whether cell phone use causes cancer.
The Federal Communications Commission (FCC) concludes that no scientific evidence establishes a causal link between wireless device use and cancer or other illnesses.
In 2015 the European Commission Scientific Committee on Emerging and Newly Identified Health Risks concluded that, overall, the epidemiologic studies on cell phone radiofrequency electromagnetic radiationexposure do not show an increased risk of brain tumors or of other cancers of the head and neck region (11
What studies are under way that will help further our understanding of the possible 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 COSMOSExit Disclaimer
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.
The challenge of this ambitious study is to continue following the participants for a range of health effects over many decades. Researchers will need to determine whether participants who leave the study are somehow different from those who remain throughout the follow-up period.
Although recall bias is minimized in studies such as COSMOS that link participants to their 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 phone company account.
Do children have a higher risk of developing cancer due to cell phone use than adults?
There are theoretical considerations as to why the possible risk should be investigated separately in children. 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 consequently 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.
Thus far, the data from studies in children with cancer 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 either by time since initiation of use, amount of use, or by the location of the tumor (23
Several studies that will provide more information are under way. Researchers from the Centre for Research in Environmental Epidemiology in Spain are conducting another international case-control study—Mobi-KidsExit Disclaimer risk factors for childhood brain tumors. Results are expected in 2018.
What can cell phone users do to reduce their exposure to radiofrequency energy?
The FDA has suggested some steps that concerned cell phone users can take to reduce their exposure to radiofrequency energy (28):
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. Exposures decline dramatically when cell phones are used hands-free.
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 (29 ID search form
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, 23,770 new diagnoses and 16,050 deaths from brain and other central nervous system
The 5-year relative survival for brain cancers diagnosed from 2005 through 2011 was 35 percent (30
The risk of developing brain cancer increases with age. From 2008 through 2012, 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
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