Diana Zuckerman, PhD, Brandel France de Bravo, MPH, and Hannah Kalvin
National Center for Health Research
You’ve probably heard news stories claiming that “cell phones are dangerous” and others claiming that “cell phones have been proven safe.” It’s hard to know what to believe-especially when we’ve grown so dependent upon these convenient communication devices.
SHOULD WE BE WORRIED?
Have you ever read the fine print in your cell phone manual? All manuals say not to hold the phone next to your ear, but how many of us actually talk on cell phones while holding them an inch away?
There have been concerns, from both scientists and the media, that cell phone usage is linked to tumor development. The extensive use of cell phones is a relatively recent phenomenon, and since cancers usually take at least 10-20 years to develop, it will be years before research is likely to conclude whether cell phones cause cancer or not. In addition, the long-term risks of cell phone use may be much higher for children than adults.
International organizations have been researching this issue. The International Agency for Research on Cancer (IARC), which is part of the World Health Organization (WHO), brought together scientists, including those with financial ties to cell phone companies, to review all relevant data on radiation from wireless handheld devices such as cell phones. This type of radiation is known as Radio Frequency-Electromagnetic Radiation (RF-EMR), also referred to as microwave radiation. The IARC concluded that the evidence suggests this radiation is “possibly carcinogenic to humans,” and that there wasn’t enough research evidence to conclude that cell phones are dangerous or that they are safe.1
This resulted in the IARC creating the Interphone Project, an international effort (that did not include the United States) to investigate the risk of tumors from cell phones. After the 10-year project was finished in February 2012, scientists found that due to biases present in the study, no strong conclusions could be made.2
The Centers for Disease Control and Prevention, or CDC, called for caution in cell phone use because of “the unresolved cancer question” in 2014. However, the CDC removed this statement from their website soon after.3 Critics assume it was removed because of political pressure from cell phone companies. Currently, the CDC says that more research is needed on this topic since “there is no scientific evidence that provides a definite answer.”4
WHAT DOES RESEARCH TELL US ABOUT CELL PHONES, TUMORS AND OTHER HEALTH ISSUES?
In 2007 and 2012, scientists published two different reviews of cell phones and brain tumors, and concluded that studies of individuals using cell phones for more than 10 years “give a consistent pattern of an increased risk for acoustic neuroma and glioma,” with the risk being highest for a tumor on the same side of the head that the phone is used.56 Gliomas are the most common cancerous brain tumor, and most gliomas are malignant (and usually fatal). Acoustic neuromas are benign tumors of the acoustic nerve that can cause deafness. These two reviews analyzed the results of 18 studies and 2 studies, respectively. However, a study published in 2013 found that while long-term cell phone use was associated with acoustic neuromas, it did not predict gliomas.7 In contrast, a study of 1,339 cell phone users, published in 2014, found that the heaviest cell phone users had an increased chance of developing gliomas. These heaviest users, who had a total of over 900 hours of cell phone usage, were found to have spent an average of 54 minutes on the phone per day.8
Animal studies contribute to these concerns. A 2015 study in Germany also identified a connection between cell phone radiation and tumor growth in mice. Researchers found that in comparison to a known cancer-causing agent, weak cell phone signals were more likely to promote tumor growth. Although this study was carried out in mice, it implies that cell phone radiation may negatively affect human health more than previously thought and that limits for cell phone radiation need to be lower.9
In May 2016, the National Toxicology Program released preliminary results from a two-year study on the impact of cell phone radiation on rats. They found that, for rats exposed to moderate to high levels of cell phone radiation, brain cancer and heart tumors called schwannomas were more likely. Even though only 4% of male rats exposed to radiation developed these tumors, they are so rare that the scientists concluded that cell phone radiation was the cause. This study is relevant to humans because humans can develop similar types of tumors.10
Although the results of studies on the effects of cell phones on the human brain are inconsistent, perhaps because cell phone use has increased over time and is rarely measured objectively, most research shows a worrisome link between cell phone use and brain tumors.
Scientists in countries around the world have published their own results on other health problems that appear to be a result of increasing cell phone usage. the following health problems connected to cell phone radiation:
- salivary gland tumors11,12
- dizziness and migraines13
- less sleep and poor sleep quality14
- changes in production of specific proteins in human cells15
- decreased sperm count and quality16,17,18
- skin irritation, especially on the face (this is a condition known as electrohypersensitivity)19,20
- behavioral problems and increased chance of cancer tumor development in children. You can read more about this here.
Meanwhile, cell phone companies continue to insist that the evidence shows that their cell phones are safe. Cell phone companies tend to draw conclusions based on the studies they funded themselves, which have always found cell phones are safe. In addition, many of those studies were conducted years ago, when cell phone usage was much lower for the average person than it is today.
CONTROVERSIES ON CELL PHONE RESEARCH RESULTS
Underlying the controversy about cell phone radiation is the belief by most physicists that cell phone radiation could not possibly cause cancer. Although epidemiological research seems to suggest otherwise, other factors make it difficult to measure the impact of cell phone use because cancer takes a very long time to develop, cell phone technology and frequency of usage has changed dramatically, and any link between cancer and cell phones could possibly be caused by unknown exposures or traits. However, the National Toxicology Program study found for the first time that cell phone radiation could, in fact, damage DNA.21 Additionally, there is potential for biases and errors in the collection of data in these studies, which could result in inaccurate conclusions. For example, many researchers questioned the Interphone study because they thought that risk was underestimated. Research is needed to determine the true effect of cell phones on the development of different cancers.
DIFFERENT TYPES OF STUDIES: HOW CAN RESEARCHERS GET TO THE BOTTOM OF THIS?
There is a consensus among researchers that retrospective studies present problems and that prospective studies are needed. Retrospective studies are ones that look back in time to study or measure risk, such as whether past cell phone use makes a person more likely to develop cancer or other health problems. But people may not remember their past behaviors accurately and researchers have no way to verify the information. Unless they use phone records, retrospective studies are also subject to “recall bias,” which means people with a disease might remember the past differently than people without a disease. In the case of cell phones, people with brain tumors may exaggerate their past cell phone use in an attempt to find an explanation for the inexplicable. An analysis published in 2015 shows that information used for many retrospective studies may not be reliable because numerous brain tumor cases are not reported to the Swedish Cancer Register, the database that has commonly been used to try to disprove any connection between cell phones and tumors.22
Prospective studies are ones that follow people over time and monitor the health problems that arise in the different groups during the study period. A prospective study of cell phone users would have to compare the health of infrequent users (controls) to heavy users (cases) but it is becoming increasingly difficult to find people who never use cell phones. In addition, any study started now would take at least 10 years to have useful information about the development of cancer; by that time, millions of people would have been harmed if cell phone radiation is dangerous.
Wireless technologies are proliferating daily, and different countries have different limits on radiation from wireless devices, which is why more and better designed research is urgently needed to determine safe levels of exposure. And yet, as noted above, it is increasingly difficult to design and conduct studies that will answer key questions anytime soon.
PRECAUTIONS YOU CAN TAKE
Scientists recognize that most people are not going to stop using cell phones. Since many studies suggest that there may be risks, experts recommend that cell phone users take some precautions:
- Limit the number of calls you make.
- Limit the length of your calls.
- Use hands-free devices (wired cell phone headsets or wireless ones like Bluetooth).
- If you are not using a hands-free device, put the cell on “speaker phone” or hold the phone away from your ear.
- When speaking on your cell phone, alternate sides.
- Avoid carrying your phone in your pocket, on your belt, or anywhere close to your body since cell phones emit radiation even when they are not in use
- Limit your cell phone use in rural areas or in any place where reception is poor. More radiation is emitted when you are farther from a cell phone tower.
- Text message instead of talking (never while driving!).
- Check out how much radiation your phone emits by looking at its SAR (specific absorption rate), which is a measure of the amount of radiation absorbed by your body. When buying a new phone, try to select one with a lower SAR. A list of cell phones with the lowest SARs can be found here. But remember, these SARs are based on a six foot tall, 200 pound man with an 11 pound head, and the levels are higher for smaller people.
Although not enough time has passed for research to agree on the exact impact of cell phones on brain tumors and other health risks, the evidence so far suggests that we should be cautious. While hands-free driving laws are resulting in greater use of ear pieces in cars, more and more people are opting not to pay for land lines and are relying exclusively on their cell phone. As a result, some adults and children are holding cell phones to their ears for hours each day.
Should we be concerned? Remember that most published studies evaluated relatively infrequent cell phone usage and that research is inadequate to draw conclusions regarding safety. The health impact of the long-term and frequent use of cell phones that is typical today could be substantially worse. And, if there is a cancer risk, we won’t see the effects of cell phone use on cancer rates for another 10-20 years. That is why it is important that researchers who do not have financial ties to cell phone companies continue long-term studies with more appropriate measures of high, medium, and low cell phone usage. In the meantime, you can play it safe and limit your cell phone use.
This article was updated in 2016.
- World Health Organization, International Agency for Research on Cancer. (2011) IARC classifies radiofrequency electromagnetic fields as possibly carcinogenic to humans. (Press release, Retrieved from href=”http://www.iarc.fr/en/media-centre/pr/2011/pdfs/pr208_E.pdf”>http://www.iarc.fr/en/media-centre/pr/2011/pdfs/pr208_E.pdf.) ▲
- Cardis E, Deltour I, Vrijheid M, Combalot E, Moissonnier M, Tardy H, et al (2010 May 17). Brain tumor risk in relation to mobile phone use: results of the INTERPHONE international case-study. International Journal of Epidemiology, 39(1): 675-694. ▲
- Microwave News (2014). CDC Calls for Caution on Cell Phones, Then Gets Cold Feet. Retrieved from: http://www.microwavenews.com/news-center/cdc-endorses-precaution ▲
- Centers for Disease Control and Prevention (2014). Frequently Asked Questions about Cell Phones and Your Health. Retrieved from: http://www.cdc.gov/nceh/radiation/cell_phones._FAQ.html ▲
- Hardell L, Carlsberg M, Soderqvist F, Hansson Mild K, Morgan LL (2007). Long-term use of cellular phones and brain tumours: increased risk associated with use 10 years. Occupational and Environmental Medicine 64(9):626-632. ▲
- Hardell L, Carlberg M, Hansson Mild K. Use of mobile phones and cordless phones is associated with increased risk for glioma and acoustic neuroma. Pathophysiology 2013;20:85–110. ▲
- Benson, V, Pirie, K, Schüz, J, Reeves, G, Beral, V, Green, J (2013 May 8). Mobile phone use and risk of brain neoplasms and other cancers: prospective study. Int. J. Epidemiol. (2013) 42 (3): 792-802. doi:10.1093/ije/dyt072 ▲
- Courau, G, Bouvier, G, Lebailly, P, Fabbro-Peray, P, Gruber, A, Leffondre, K, Guillamo, J, Loiseau, H, Mathoulin-Pélissier, S, Salamon, R, Baldi, I (9 May 2014). Mobile phone use and brain tumours in the CERENAT case-control study. Occup Environ Med, 71(7): 514-522. doi:10.1136/oemed-2013-101754 ▲
- Lerchl, A., Klose, M., Grote, K., et al. (2015). Tumor promotion by exposure to radiofrequency electromagnetic fields below exposure limits for humans. Biochemical and Biophysical Research Communications, 459(4), Pages 585-590. Retrieved from: http://www.sciencedirect.com/science/article/pii/S0006291X15003988 ▲
- “Report of Partial Findings from the National Toxicology Program Carcinogenesis Studies of Cell Phone Radiofrequency Radiation in Hsd: Sprague Dawley SD rats (Whole Body Exposures).” National Toxicology Program 2016. href=”http://biorxiv.org/content/biorxiv/early/2016/05/26/055699.full.pdf”>http://biorxiv.org/content/biorxiv/early/2016/05/26/055699.full.pdf ▲
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- Fejes I, Zavaczki Z, Szollosi J, Koloszar S, Daru J, Kovacs L, et a; (2005 Sept-Oct). Is there a relationship between cell phone use and semen quality? Arch Androl, 51(5): 385-393. Retrieved from href=”http://www.ncbi.nlm.nih.gov/pubmed/16087567″>http://www.ncbi.nlm.nih.gov/pubmed/16087567. ▲
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- Yakymenko, I., Tsybulin, O., Sidorik, E., et al. (2015). Oxidative mechanisms of biological activity of low-intensity radiofrequency radiation, Electromagnetic Biology and Medicine. Retrieved from: http://dx.doi.org/10.3109/15368378.2015.1043557 ▲
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