research topics on cell phone radiation

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Methodology of Studying Effects of Mobile Phone Radiation on Organisms: Technical Aspects

The negative influence of non-ionizing electromagnetic radiation on organisms, including humans, has been discussed widely in recent years. This paper deals with the methodology of examining possible harmful effects of mobile phone radiation, focusing on in vivo and in vitro laboratory methods of investigation and evaluation and their main problems and difficulties. Basic experimental parameters are summarized and discussed, and recent large studies are also mentioned. For the laboratory experiments, accurate setting and description of dosimetry are essential; therefore, we give recommendations for the technical parameters of the experiments, especially for a well-defined source of radiation by Software Defined Radio.

1. Introduction

With the rapid development of wireless communication, the exposure of people to non-ionizing electromagnetic radiation, especially from mobile phones, is growing rapidly, raising concerns about its possible effects on human health.

This paper deals with the main problems of experiments studying the effects of mobile phones on human health, namely on cells and DNA. We focus on scientific methods, refer to their advantages and difficulties and give recommendations for future research, especially in the technical aspects of the experiments.

1.1. Types of Studies of Biological Effects

From the possible effects of radiofrequency radiation on the human body, the most studied are the effects on the brain, cancer incidence, and fertility, including induction of certain enzymes, neurological symptoms, toxicological effects, genotoxicity, carcinogenicity, and decreasing the fertilizing potential of sperm cells. The published literature studies the influence of radiofrequency radiation on mitochondria, apoptosis pathways, heat shock proteins, free radical metabolism, cell proliferation, cell differentiation, DNA damage, the plasma membrane, etc. [ 1 , 2 , 3 , 4 , 5 ].

The biological effects of radiofrequency radiation can be researched by three basic types of studies: laboratory studies in vivo, in vitro, and epidemiological studies, which will not be further discussed in this paper.

1.1.1. Laboratory Studies In Vivo

In in vivo research methods, laboratory animals are exposed to radiofrequency radiation, and the effects of the exposure are evaluated, e.g., samples of cells or tissues are collected to study possible damage. The laboratory studies allow better control of the experimental conditions compared to epidemiological studies and help to answer basic questions. The problem of these studies is often the number of samples, which in many cases is not high enough to make a statistically significant conclusion. Furthermore, the application of the results on humans is always problematic [ 6 ]. Zhu et al. [ 7 ] suggest that larger animals (e.g., rabbits) are more similar to humans in many aspects (e.g., skull thickness) and, therefore, more suitable for radiofrequency radiation experiments. Comparisons of in vivo experiments are mostly difficult because many different experimental settings are used [ 8 ].

1.1.2. Recent Large In Vivo Studies

Recently extensive rodent toxicology and carcinogenesis studies were carried out in the US National Toxicology Program (NTP). Two different types, or modulations, of radiofrequency radiation (GSM and CDMA) commonly used in mobile phone networks in the United States, were used to expose rats and mice to identify potential toxicity or cancer-related hazards. Animals were exposed to radiofrequency radiation for 18 h per day with 10 min off/on cycles, 7 days per week, for up to 2 years. There were 90 male and 90 female animals in each group. Whole-body SAR exposures of 0, 1.5, 3, or 6 W/kg at 900 MHz were used for rats. Whole-body SAR exposures of 2.5, 5, or 10 W/kg at 1900 MHz were used for mice [ 9 , 10 ]. The doses of radiation in the studies were generally higher than those used in mobile phones. The lowest exposure level used in the studies was equal to the current local tissue exposure limit.

A genetic toxicology study with analysis of the comet assay and micronucleus assay was also performed (for five different tissues per animal) [ 9 , 10 ].

Follow-up studies by the NTP to investigate mechanisms of genetic damage are underway [ 11 ]. For future studies, NTP wants to focus on developing measurable physical indicators, or biomarkers, of potential effects of radiofrequency radiation. These may include changes in metrics, such as DNA damage in exposed tissues, which can be detected much sooner than cancer [ 12 ].

Another large recent study was performed by the Ramazzini Institute in Italy. Rats were exposed for 19 h/day to a 1.8 GHz GSM far-field of 0, 5, 25, or 50 V/m (SAR up to 0.1 W/kg) from the prenatal period until natural death [ 13 ].

Both NTP (simulating near field exposure from a mobile phone) and the Ramazzini study (simulating far-field exposure from a base station) used simulated radiofrequency signals emitted by generators. The strength of the studies is that they exactly controlled how much radiofrequency radiation the animals received [ 12 ]. The disadvantage of these studies (from the technical point of view) is the use of a signal generator, i.e., the absence of the unpredictable changes of the radiofrequency signal (in contrast to the real phone signal, as discussed in Section 2 .). Other general possible shortcomings of the NTP study are discussed in [ 14 ] and shortcomings of Ramazzini and other studies in [ 15 ].

1.1.3. Laboratory Studies In Vitro

In vitro studies usually use different types of cells that are exposed to radiation in a special container. After, the exposure of the damage to the cells is evaluated (e.g., their viability and DNA damage). Therefore, for in vitro experiments, comparison or reproducibility is a challenge. This is not only due to different experimental settings but can be caused even by slight modifications of the evaluating methods [ 8 , 16 ].

2. Experiments Investigating the Effects of Radiofrequency Radiation on Cells and DNA

Carcinogenic growth is mostly initiated by damage to the cell’s genome, and therefore, many studies have investigated the effects of electromagnetic fields on DNA and chromosomal structure [ 16 ].

2.1. Experimental Settings

The published experiments studying the effects of radiofrequency radiation differ in the type of investigated cells, frequency and intensity of the electromagnetic radiation, time of exposure, and methods evaluating the effects of exposure on cells and DNA. The most important parameters of the experiments are summarized below [ 8 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ]:

Both in vitro and in vivo methods are used.

The studies use different types of cells. The cells may originate either from animals, mostly laboratory mice and rats, or humans. The cells can be freshly collected (e.g., lymphocytes, leukocytes, sperm, or skin cells) or cultured (e.g., brain tumor, lung, skin, or stem cells).

Specific Energy Absorption Rate (SAR)

The value of SAR in published works reaches mostly from <1 to 5 W/kg, higher SAR values are less frequent. In some papers, the SAR value is not given at all.

Different frequencies are used, most works use frequencies ≤2000 MHz, and some are around 2500 MHz. Higher frequencies are rarely used.

Other parameters of the radiation

Power intensity of the radiation and exposure time are crucial parameters. Other important characteristics of electromagnetic radiation are variability, modulation (continuous or pulse-modulated waves), or shape of the waves (square or sine waves).

Sources of radiation

Many studies use usual mobile phones to expose the samples or animals, often alternation of standby mode and dial mode is used. It is also obvious that the generation of mobile technology used, e.g., 2G (GSM), 2,5G (GPRS), 3G (LTE), plays a role. Another possibility is a source of radiofrequency radiation, where exact parameters (e.g., frequency) can be set.

The above-mentioned parameters are very important, and even slight variations can lead to discrepant results in seemingly similar studies [ 16 ]. According to Saliev et al. [ 19 ], the most important parameters are the used cell line and the type of radiation (frequency, but also modulation and shape of the waves). Moreover, the conditions in cell culture incubators should be controlled carefully. A study by Mild et al. [ 23 ] detected enhanced levels of extremely low-frequency magnetic fields in cell culture incubators, which can have a significant influence on the cell cultures.

A review by Panagopoulos [ 24 ] comes to an important conclusion that once the electromagnetic field is polarized, includes extremely low frequencies, and has adequate intensity, then the main parameter is variability. It suggests the extreme and unpredictable variability of the real mobile telephone signals seems to be the main reason for the corresponding bioactivity.

2.2. Dosimetry

Exposure to a uniform electromagnetic field results in a non-uniform deposition and distribution within the body and, therefore, a dosimetric approach, measurements, and calculations are necessary. A detailed description of the dosimetry and related methods and calculations is provided in Appendix A of the new ICNIRP Guidelines [ 1 ]. Very important is Specific Energy Absorption Rate (SAR, used below 6 GHz) or Absorbed Power Density (above 6 GHz). Measuring the SAR value is very complex because SAR depends on many factors, e.g., type of mobile phone, shape and size of the body or its part, dielectric properties of the tissue, position of the source, influence of surrounding objects, and frequency of electromagnetic waves [ 1 , 5 , 25 ].

In real conditions, there are several factors influencing the exposition to mobile phones, mainly:

Time of active use of the phone
Using of speaker mode or hands-free device
Distance and visibility of the nearest mobile phone tower
The amount of mobile phone traffic in a certain place and time
The model of mobile phone

2.3. Evaluated Parameters

The most important methods for evaluating the degree of damage to cells, chromosomes, and DNA are: the comet assay (measuring number of DNA strand breaks), gamma-H2AX detection, test of chromosomal aberration induction, micronucleus test, sister chromatid exchanges, examination of cell proliferation and cell cycle distribution, and detection of apoptosis [ 5 , 18 , 26 ]. Chromosomal and DNA damage should always be evaluated using more of the mentioned tests [ 5 ], and the results should be compared, combined, and interpreted carefully.

3. Main Technical Aspects of Laboratory Experiments

In laboratory experiments with live animals, many factors, such as stress, hormonal state, or seasonal effects, can play a role. In vitro studies examining the effects of radiofrequency radiation on cells appear easier to control, evaluate, and quantify. However, for the in vitro studies, it is also complicated to compare the results, especially when the experimental conditions are not carefully defined and described.

Experiments using different biological systems are difficult to compare because different cells and organisms may not respond to electromagnetic radiation in the same way.

Further, preparing and setting the technical part of the experiment (i.e., transmitter/transceiver), as well as evaluation and interpretation of the results, can be problematic, because the technologies and dosimetry may be outside the experience of the biomedical scientists [ 16 ].

Using a common mobile phone for the experiments implies problems with an accurate assessment of the dosimetry; thus, the experiments are neither well controlled nor repeatable (real mobile phone signal depends on many factors and is always unique for the given place and time). On the other hand, recent reviews by Panagopoulos [ 24 , 27 ] emphasize that the reaction to exposure is very different when comparing exposure to a uniform source (stable frequency and intensity) with exposure to a real mobile phone, with the highly and unpredictably variable signal. He states, based on the reviews of published peer-reviewed studies [ 24 , 27 ], even simulated mobile phone signals with regular pulsing will not have the same effect as a real, unpredictable mobile phone signal, i.e., that the variability makes the mobile phone signal more bioactive. In other words, the more variable the signal is, the more difficult it is for the organisms to adapt to it.

The results of the published research experiment reporting the health effects of radiofrequency radiation are often inconsistent and ambiguous in mutual comparison. It is often difficult to judge the differences in the studies, which wanted to repeat and test a previous study, and sometimes got discrepant results. However, what might appear inconsistent is indeed consistent with bimodal effects reported in hundreds of publications [ 8 , 16 ]. Generally, bimodal effects can be caused by the concentration of an agent, time of exposure, and many other parameters of the studied system. The results of the published research experiments show that the interaction of electromagnetic fields with DNA is very complex and depends on many factors, such as conditions of irradiation, cell type, and intensity and duration of the exposition [ 16 ].

Development of Mobile Phone Technologies (Radiofrequency Sources)

The parameters of the telecommunication part of the experiments are very important and should be well controlled. Unfortunately, the radiofrequency radiation sources used in the studies are mostly either not well defined and controlled (a usual mobile phone), or do not simulate the unpredictable changes of the real mobile phone radiofrequency radiation (a vector signal generator). In recent years, new generations of mobile network technologies were introduced: 4G, using frequencies up to 8 GHz (mostly up to 2500 MHz [ 28 ]) and 5G [ 29 ], using frequencies below 6 GHz and up to 86 GHz (24.25–27.5 GHz for Europe [ 30 , 31 ]), i.e., new frequency bands and wider spectral bandwidth per frequency channel are assigned [ 32 , 33 ]. The future use of these higher frequencies and the need for a denser network of base stations is currently initiating debates about the influence of the 5G mobile infrastructure on organisms and human health. A new review by Karipidis et al. [ 17 ] found no confirmed evidence that low-level RF fields above 6 GHz are hazardous for human health. A review by Simkó and Mattsson [ 34 ] pointed out there were no consistent relationships between power density, exposure duration or frequency, and exposure effects in studies. Kostoff et al. [ 35 ] emphasize 5G technology can have effects other than only surface effects (on skin or eyes). It is obvious the results of older experiments, i.e., mobile phones/networks, do not apply to the new technologies due to new frequency bands, the number of antennas, modulation techniques, access methods, scheduling, etc., collectively called a radio access network.

4. Discussion

Despite the number of published works about genotoxicity and carcinogenicity of radiofrequency radiation, it cannot be definitely concluded if and to what extent this radiation is harmful (under normal circumstances and observing the safety limits) [ 1 , 36 , 37 ]. Harmful effects cannot yet be excluded, especially after the long exposure (many years) to low doses, which are typical for today’s population. Moreover, considering the quick development of mobile technologies, new experiments simulating and testing the effects of these new technologies are necessary. This implies that the effects of radiofrequency radiation will still be studied in the future, using both wider and better-defined in vivo studies, as well as laboratory experiments using ever more sensitive modern methods. In the large volume of published data, there is a key to finding the conditions that initiate DNA changes and to select suitable scientific methods for future studies [ 16 ].

The Organization for Economic Co-operation and Development (OECD) issued guidelines for the testing of genetic toxicity [ 38 ]. For basic principles of selecting and treating laboratory animals in in vivo experiments, the OECD guidelines for conduction of toxicity and carcinogenicity studies [ 39 ] and the National toxicology program specifications [ 40 ] provide detailed instructions. These include recommendations regarding the number of animals in study groups, details on housing and diet, and continuous (e.g., weight) and final (e.g., histopathology) evaluation. A “checklist” for a good quality study and publication is summarized in [ 20 ].

It is very important to clearly set, follow, note, and describe the conditions of the experiments. A methodology can be based on subjective and objective evaluation methods known from telecommunication technology for Quality of Service/Quality of Experience (QoS/QoE) evaluation [ 41 , 42 ].

Based on the literature review, we recommend the following points to be considered during the implementation and evaluation of experiments, Table 1 .

Recommendation for conditions of the laboratory experiments.

Moreover, we emphasize that the dosimetry should always be clearly set and observed in the laboratory tests. This includes using a radiofrequency radiation source where the frequency, time, and intensity of the radiation, including placement of the radiation source, can be precisely set and controlled. To comply with the above-mentioned criteria—precisely defined radiofrequency radiation on the one hand, and unpredictable changes of the signal on the other hand—we suggest using the Software Defined Radio (SDR) approach available for 2G, 3G [ 44 , 45 ], 4G, and 5G [ 46 ] instead of a signal vector generator or undefined cell phone. The SDR transceiver enables the generation of high-frequency multichannel/wideband power signals in repeatable scenarios (recorded signal or artificial signal), with respect to timing, modulation methods, waveform, transmission power, and its time changes, etc., of real mobile phone radio channel parameters and for different xG mobile generations, unlike a standard signal generator. In order to be able to repeat the experiments in a controlled manner, it is necessary to use a standardized antenna adapter for radiating high-frequency power, i.e., an antenna structure for near/far EM field. The SDR enables the creation of a new base transceiver station (2G), Node B (3G), eNode B (4G), or gNode B (5G), which directly communicates with mobile phones, i.e., it can generate a real unpredictable mobile phone signal (i.e., signal changing in an irregular, unpredictable way), as suggested by Panagopoulos [ 24 ]. In addition, the SDR also enables the creation of a mobile phone phantom, i.e., specific hardware solution, e.g., OsmocomBB [ 44 ], with a well-defined mobile phone phantom (antenna, controlled radiofrequency signal radiation setup, etc., in standardized measurement environment, i.e., measurement cell), which can facilitate the reproducibility of future experiments. All necessary parameters of individual mobile technologies, including time intervals, frequency, modulation, intensity, etc., can be precisely controlled. Using the SDR and standardized measurement cell could substantially help to avoid problems of the replication of studies. In addition, one of the advantages of this approach is the possibility of sharing a specific scenario between laboratories in order to ensure the repeatability of the radiation source.

5. Conclusions

The paper reviews laboratory methods studying the effects of radiofrequency radiation on organisms, focusing on technical aspects of the experiments. As can be concluded from many works, the effects of radiofrequency radiation can differ under different conditions and settings. Therefore, we emphasize that the methodology should be clearly and precisely set to ensure the results can be verified and reproduced. Very important is the choice of a suitable source of radiation, here we recommend the SDR, which can simulate a real mobile phone signal in a controlled and repeatable way. The influence of radiofrequency radiation is a multidisciplinary topic and includes many fields, such as medicine, biology, toxicology, physics, electrical and electronic engineering, telecommunication, and statistics. The future research requires close cooperation of scientists from all these fields. Following the given recommendations should increase the overall quality of the experiments and publications and give the possibility to compare, reproduce, and verify the results.

Author Contributions

K.B. prepared the first draft of the manuscript. M.N. and L.V. contributed conceptually to the manuscript and supervised the work. M.N. critically revised the manuscript and originally contributed to the methods. All authors have read and agreed to the published version of the manuscript.

This work was funded by the Czech Technical University in Prague with the grant number SGS21/161/OHK3/3T/13.

Informed Consent Statement

Not applicable.

Conflicts of Interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

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Major Cell Phone Radiation Study Reignites Cancer Questions

Exposure to radio-frequency radiation linked to tumor formation in rats

By Dina Fine Maron on May 27, 2016

Major Cell Phone Radiation Study Reignites Cancer Questions

Federal scientists released partial findings Friday from a $25-million animal study that tested the possibility of links between cancer and chronic exposure to the type of radiation emitted from cell phones and wireless devices. The findings, which chronicle an unprecedented number of rodents subjected to a lifetime of electromagnetic radiation starting in utero, present some of the strongest evidence to date that such exposure is associated with the formation of rare cancers in at least two cell types in the brains and hearts of rats. The results , which were posted on a prepublication Web site run by Cold Spring Harbor Laboratory, are poised to reignite controversy about how such everyday exposure might affect human health.

Researchers at the National Toxicology Program (NTP), a federal interagency group under the National Institutes of Health, led the study. They chronically exposed rodents to carefully calibrated radio-frequency (RF) radiation levels designed to roughly emulate what humans with heavy cell phone use or exposure could theoretically experience in their daily lives. The animals were placed in specially built chambers that dosed their whole bodies with varying amounts and types of this radiation for approximately nine hours per day throughout their two-year life spans. “This is by far—far and away—the most carefully done cell phone bioassay, a biological assessment. This is a classic study that is done for trying to understand cancers in humans,” says Christopher Portier, a retired head of the NTP who helped launch the study and still sometimes works for the federal government as a consultant scientist. “There will have to be a lot of work after this to assess if it causes problems in humans, but the fact that you can do it in rats will be a big issue. It actually has me concerned, and I’m an expert.”

More than 90 percent of American adults use cell phones. Relatively little is known about their safety, however, because current exposure guidelines are based largely on knowledge about acute injury from thermal effects, not long-term, low-level exposure. The International Agency for Research on Cancer in 2011 classified RF radiation as a possible human carcinogen. But data from human studies has been “inconsistent,” the NTP has said on its website. Such studies are also hampered by the realities of testing in humans, such as recall bias—meaning cancer patients have to try to remember their cell phone use from years before, and how they held their handsets. Those data gaps prompted the NTP to engage in planning these new animal studies back in 2009.

The researchers found that as the thousands of rats in the new study were exposed to greater intensities of RF radiation, more of them developed rare forms of brain and heart cancer that could not be easily explained away, exhibiting a direct dose – response relationship. Overall, the incidence of these rare tumors was still relatively low, which would be expected with rare tumors in general, but the incidence grew with greater levels of exposure to the radiation. Some of the rats had glioma—a tumor of the glial cells in the brain—or schwannoma of the heart. Furthering concern about the findings: In prior epidemiological studies of humans and cell phone exposure, both types of tumors have also cropped up as associations.

In contrast, none of the control rats—those not exposed to the radiation—developed such tumors. But complicating matters was the fact that the findings were mixed across sexes: More such lesions were found in male rats than in female rats. The tumors in the male rats “are considered likely the result of whole-body exposure” to this radiation, the study authors wrote. And the data suggests the relationship was strongest between the RF exposure and the lesions in the heart, rather than the brain: Cardiac schwannomas were observed in male rats at all exposed groups, the authors note. But no “biologically significant effects were observed in the brain or heart of female rats regardless of modulation.” Based on these findings, Portier said that this is not just an associated finding—but that the relationship between radiation exposure and cancer is clear. “I would call it a causative study, absolutely. They controlled everything in the study. It’s [the cancer] because of the exposure.”

Earlier studies had never found that this type of radiation was associated with the formation of these cancers in animals at all. But none of those studies followed as many animals, for as long or with the same larger intensity exposures, says Ron Melnick, a scientist who helped design the study and is now retired from the NTP.

The new results, published on Web site bioRXiv, involved experiments on multiple groups of 90 rats. The study was designed to give scientists a better sense of the magnitude of exposure that would be associated with cancer in rodents. In the study rats were exposed to RF at 900 megahertz. There were three test groups with each species of each sex, tested at different radiation intensities (1.5, three and six watts per kilogram, or W/kg), and one control group. (The lowest-intensity level roughly approximates the levels allowed by U.S. cell phone companies, which is 1.6 W/kg .) “There are only 90 animals per group, so because there is a trend — and this is the purpose of these assays where you do multiple doses you extrapolate downward and calculate a risk for humans from those trends — so that information is useful. Probably what caused cancer at the high doses will cause cancer at lower doses but to a lesser degree,” Portier says.

Rodents across all the test groups were chronically exposed to RF for approximately nine hours spread out over the course of the day. (Their entire bodies were exposed because people are exposed to such radiation beyond their heads, especially when they carry them or store them in their bras, says John Bucher, the associate director of the NTP.) During the study the rats were able to run around in their cages, and to eat and sleep as usual. The experiments also included both types of modulations emitted from today’s cell phones: Code Division Multiple Access and Global System for Mobile. (Modulations are the way the information is carried, so although the total radiation levels were roughly the same across both types, there were differences in how radiation is emitted from the antenna—either a higher exposure for a relatively short time or a lower exposure for a longer time.) Overall, there was no statistically significant difference between the number of tumors that developed in the animals exposed to CDMA versus GSM modulations. With both modulations and tumor types, there was also a statistically significant trend upward—meaning the incidence increased with more radiation exposure. Yet, drilling down into the data, in the male rats exposed to GSM-modulated RF radiation the number of brain tumors at all levels of exposure was not statistically different than in control males—those who had no exposure at all. “The trend here is important. The question is, ‘Should one be concerned?’ The answer is clearly ‘Yes.’ But it raises a number of questions that couldn’t be fully answered, ” says David Carpenter, a public health clinician and the director of the Institute for Health and the Environment at the University at Albany, S.U.N.Y.

The findings are not definitive, and there were other confusing findings that scientists cannot explain—including that male rats exposed to the radiation seemed to live longer than those in the control group. “Overall we feel that the tumors are likely related to the exposures,” says Bucher, but such unanswered questions “have been the subject of very intense discussions here.”

The NTP released the partial findings on Friday after an online publication called Microwave News reported them earlier this week. The program will still be putting out other results about the work in rats and additional findings about similar testing conducted in mice. The NIH told Scientific American in a statement, “This study in mice and rats is under review by additional experts. It is important to note that previous human, observational data collected in earlier, large-scale population-based studies have found limited evidence of an increased risk for developing cancer from cell phone use.” Still, the NTP was clearly expecting these findings to carry some serious weight: Ahead of Friday’s publication the NTP said on its Web site that the study (and prior work leading to these experiments) would “provide critical information regarding the safety of exposure to radio-frequency radiation and strengthen the science base for determining any potential health effects in humans.”

In response to media queries, cell phone industry group CTIA – The Wireless Association issued a statement Friday saying that it and the wireless industry are still reviewing the study’s findings. “Numerous international and U.S. organizations including the U.S. Food and Drug Administration, World Health Organization and American Cancer Society have determined that the already existing body of peer-reviewed and published studies shows that there are no established health effects from radio frequency signals used in cellphones,” the CTIA statement said.

The Federal Communications Commission, which had been briefed by NIH officials, told Scientific American in a statement, “We are aware that the National Toxicology Program is studying this important issue. Scientific evidence always informs FCC rules on this matter. We will continue to follow all recommendations from federal health and safety experts including whether the FCC should modify its current policies and RF exposure limits.”

This animal study was designed primarily to answer questions about cancer risks humans might experience when they use phones themselves, as opposed to smaller levels of exposure from wireless devices in the workplace or from living or working near cell phone towers. But it may have implications for those smaller levels as well, Portier says.

The findings shocked some scientists who had been closely tracking the study. “I was surprised because I had thought it was a waste of money to continue to do animal research in this area. There had been so many studies before that had pretty consistently not shown elevations in cancer. In retrospect the reason for that is that nobody maintained a sufficient number of animals for a sufficient period of time to get results like this,” Carpenter says.

Exposing rodents to radiation for this type of experiment is a tricky business. First, scientists need to be able to calculate exactly how much the rats should be exposed to relative to humans. Too much exposure would not be a good proxy for human use. And with finely calculated low-level exposure rates, scientists still need to be sure they are not going to heat the animals enough to kill them or to cause other health problems. (Subsequent work will be published on the animals’ temperatures.)

The fact that scientists were able to expose animals to nonionizing radiation (like that emitted by cell phones) and those animals went on to develop tumors but that exposure did not significantly raise the animals' body temperatures was “important” to release, Bucher says.

There are safety steps individuals can take, Carpenter says. Using the speakerphone, keeping the phone on the desk instead of on the body and using a wired headset whenever possible would help limit RF exposure. “We are certainly not going to go back to a pre-wireless age,” he says. But there are a number of ways to reduce exposure, particularly among sensitive populations.”

Editor's Note (5/27/16, 2:10 P.M.): This story was updated to reflect information provided during an NTP press conference and a statement from an industry group.

ABOUT THE AUTHOR(S)

Dina Fine Maron, formerly an associate editor at Scientific American , is now a wildlife trade investigative reporter at National Geographic . Follow Dina Fine Maron on Twitter Credit: Nick Higgins

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Cell Phone Radiation Health Effects Questions

Q: Is cell phone radiation dangerous?

A: An ever growing body of evidence shows that cell phone and wireless radiation – at even very low levels- could harm our health in a number of different ways. In 2011 the World Health Organization (WHO) classified cell phone radiation as a Class 2 B Carcinogen “possibly carcinogenic to humans”—in the same category as lead, engine exhaust, DDT, and jet fuel. Studies in Europe show that people who used cell phones heavily for over ten years have a doubled risk of brain cancer, and those who begin using cell phones as teenagers have a four to five times higher chance of being diagnosed with brain cancer.

A Yale study funded by the American Cancer Society found an association between thyroid cancer and cell phone use in people with certain genetic susceptibilities.

As of 2020, several expert independent scientists have published their evaluation that the evidence has increased and this radiation is a human carcinogen.

The 10-year $30 million National Institute of Environmental Health Sciences National Toxicology Program’s (NTP) Studies of Cell Phone Radiation found that chronic exposure to RFR was associated with “clear evidence” of cancer in RFR-exposed male rats.In addition, exposed animals had significantly more DNA damage, heart damage and low birth weight. The NTP findings were supported by the Ramazzini Institute study which found the same types of cancers the NTP found, yet at much lower levels (levels lower than FCC limits as the Ramazzini study was designed to replicate base station/ cell tower exposures). The NTP and Ramazzini findings in animals are further corroborated by research on humans that found people who use cell phones over 10 years “heavily” (defined in these studies as around 30 minutes per day) developed increased tumors—schwannomas and glioblastomas—the same cell type as found in the NTP and Ramazzini Institute studies.

Q: Can cell phones impact memory? I feel like I am more forgetful.

A major research study found decreased memory among teenagers with higher cell phone exposures to the brain after one year of repeated exposure. This study replicated previous findings. A major NIH study found that even very low levels of microwave radiation from cell phones can change brain function. Another study on 4G technology showed that the radiation affected brain neural activity not only in the closer brain region but also in the remote region, including the left hemisphere of the brain.

Experimental research shows that animals exposed prenatally to cell phone radiation develop more damage to critical parts of the brain involved in thinking and impulse control–the hippocampus and cerebellum. In 2012, Yale research demonstrated that when pregnant mice were exposed to cell phone signals, their offspring had much greater levels of hyperactivity, impaired memory and impaired brain development in the part of the brain linked to ADHD.

EHT has convened several expert conferences where scientists have presented their research on cell phones impact to brain development. For example at the Commonwealth Club in 2013 , scientists detailed the science showing brain, breast cancer, and reproductive organ impacts. At this conference, Dr. Suleyman Kaplan presented his research showing significant changes in brain neuron development after exposure to this radiation. You can read his letter to the FCC detailing his research findings and calling for more protective limits.

Scientists in Korea have additionally found something called Digital Dementia in children. They reported that children who are heavy technology users have brains that are underdeveloped on the right side. This has been characterized by memory loss, attention disorders, lack of eye contact, lack of empathy, and difficulty feeling or showing emotions. As a result, the Korean government is instituting programs to reduce uses and exposures, especially to young children.

Q: What other health impacts are associated with cell phones?

Effects documented in published studies have found not only increased cancer risk , but also increased cellular stress , increased harmful free radicals , genetic damages , structural and functional changes of the reproductive system , learning and memory deficits , behavioral problems , neurological disorders , headaches , and negative impacts on general well-being in humans.

Recent research also demonstrates a wide variety of cellular damage experimentally including increased oxidative stress from cell phone and wireless radiation. Oxidative stress is important to the development of cancer, among other things, because it essentially disrupts the normal redox state of cells, damaging cells and their DNA through the production of peroxides and free radicals. A 2015 research review showed that peer-reviewed research that looked at oxidative stress showed effects in 93 out of 100 studies. Read more research studies on our webpage dedicated to the science here .

Q: Why do you say we should not carry phones in our pocket?

A: Wireless radiation has been shown to harm the reproductive system as well. Many experiments have been conducted on wireless radiation and sperm. Scientists at the Cleveland Clinic and major research centers around the world have repeatedly found that sperm from healthy men that are exposed to cell phone radiation die three times more quickly and develop three times more damage to mitochondrial DNA than sperm from the same men that are not exposed. Several research reviews indicate reproduction related health problems from cell phones.

Q: I carry my cell phone in my bra. Is this OK?

A: Case studies show young women who stored their cell phones in their bra for years developed unusual tumors right below the location of the antennas where they kept their phone. These women had no history of breast cancer or genetic predisposition to the disease, yet developed the unusual cancers at a young age. Learn more about cell phones and breast cancer here.

Q: What about cell phone towers?

There is a growing body of evidence connecting a myriad of health issued to proximity to cell phone towers. In densely populated cities, there are often a great number of people living close to cell phone towers, and research is documenting that these people are reporting a variety of ailments, including difficulty sleeping, nausea, cancer and more.

However, it is often hard to quantify what people’s actual exposure is in cell towers studies. This is why experimental research is so important. Experimental studies link the radiation from cell towers- called radiofrequency- to cancer and biological effects. Read more research related to cell towers here.

Q: Is anyone doing anything about it?

Berkeley California has passed a cell phone right to know ordinance informing people about the radiation emissions from their phones. Several cities have passed proclamations on cell phone radiation.

Although the FCC is moving full steam ahead with 5G, US states are starting to recognize the lack of accountability. Oregon passed a bill , SB283, which directs the Oregon Health Authority to review peer-reviewed, independently funded scientific studies of health effects of exposure to microwave radiation, particularly exposure that results from use of wireless network technologies in schools.

New Hampshire passed HB 522 “ An act establishing a commission to study the environmental and health effects of evolving 5G technology” which created an expert Commission to study the health and environmental impacts of 5G.

Over 20 countries have policies in place to educate the public on reducing cell phone radiation. Russia, the UK, Canada, and many other countries discourage the use of cell phones by children, and France and Belgium have actually banned the sale of phones to children. Toronto, Canada limits Wi-Fi in public parks. Several local governments ban cell towers on schools or near hospitals. Please see our web page on policy to read the full list.

Q: What about children and cell phones?

A: Cell phones are not safe for children because they are more vulnerable. On July 12, 2012, the American Academy of Pediatrics (AAP) sent a letter to the Federal Communications Commission (FCC) urging the FCC to open a formal inquiry into radiation standards for cell phones and other wireless products because children are more vulnerable to wireless radiation. They state that “The FCC has not assessed the standards for cell phone radiation since 1996” and “children are… disproportionately impacted by all environmental exposures, including cell phone radiation”

Current standards were not developed with children’s vulnerabilities in mind. Federal standards are based on an adult male model. Keeping wireless devices close to the pregnant abdomen is potentially dangerous because the developing fetus is especially susceptible to radiation. This is why many doctors and obstetricians recommend reducing cell phone and wireless exposures for pregnant women. See the BabySafe Project .

Keep in mind that the brain does not complete development until the mid-twenties. This means children deserve an additional level of precaution. Small insults on the developing brain can result in large impacts later in life. Their skulls are softer and thinner than an adult’s skull, and they also have more fluid content than an adult. The radiation is absorbed more deeply into children’s brains and therefore, children need greater protections in place.

Q: What research has been done on children?

A: It is unethical to experiment on children. Yet in a way, all the children in this world are in an experiment, without controls. Although there are not scientists purposefully exposing children to cell phone radiation and testing them afterwards, scientists are following children, determining their cell phone radiation exposures and analysing if those with higher exposures have health effects. As an example, the research study on teenagers found decreased memory after one year. Researchers have also found that higher cell phone radiation exposure was associated with increased ADHD symptoms in children with lead levels in their blood.

Recent research using highly sophisticated computer modeling continues to show that children absorb microwave radiation deeper into their brains as compared to adults. The World Health Organization’s International Agency for Research on Cancer’s 2013 Monograph on Radiofrequency details research showing how “the average radio-frequency energy deposition is twice as high in certain regions of children’s brains and up to 10 times higher in the bone marrow of children’s skulls, compared to energy deposition in adult brains and skulls.”

In 2008 the National Research Council issued a report, calling for “investigation of the potential effects of RF fields in the development of childhood brain tumor” observed that “with the rapid advances in technologies and communications utilizing [radiation in the range of cell phone frequencies], children are increasingly exposed… at earlier ages (starting at age 6 or before)” and “Children will be exposed to cell phone radiation for more years and therefore in greater total amounts than the current generation of adults”.

To this date, the necessary comprehensive research necessary to understand the full myriad of risks to children has simply not been done. However, the accumulated research showing effects on the developing brain and immune system are more than enough to show that children are more vulnerable and face far greater health risks than adults.

MOBI-KIDS is an ongoing 14 country study looking at cell phones and the risk of brain cancer in children. Results have not been released.

Q: What about studies showing no effect from wireless exposures?

A: Often-cited studies seem to imply that no health effects are found; however, much of this research was done or funded by the cell phone companies, which has led to biased results. This bias ultimately misinforms people about how wireless radiation can affect our body. In addition, many often-cited studies minimize possible health risks from this radiation because the studies did not look at impacts over the long term. For example, it is the research that looked at impacts over ten years of cell phone use (30 min a day) that showed increased brain cancer. On the other hand, studies that looked only at 5 years to 7 years of use did not show health effects.

Some studies are put forward that seem to show “no risk”. Then a deeper analysis of the study shows serious methodological flaws. For example, concerning the often referred to Danish Cohort study please see the published commentary . It is notable that the World Health Organization’s IARC explicitly rejected this widely publicized study from Denmark on brain cancer and cell phones in the British Medical Journal because it lacked detailed information on phone use and the power to find any change in risk. Yet governments continue to cite as support for “no risk”.

As another example, take the often cited 2011 CEFALO study, an international multicenter case-control study which concluded that there was an “absence of an exposure-response relationship” regarding brain tumors and mobile phone use. However, this research only looked at 7 years and brain tumors can take at least 10 years to develop. The study has been highly criticized by experts who later analyzed a subset of the data and found a highly significant association between time since first subscription and brain tumor risk. In other words, the study’s own data contradicts the conclusion that states there is “no evidence”. Please see the Commentary The JNCI Study by Aydin et al on Risk of Childhood Brain Cancer from Cell Phone Use Reveals Serious Health Problems.

The EHHI Expert group also commented on the limits of the CEFALO study in their Cell Phone Report . The study data actually shows an increased risk in the heavy cell users in this study and a shortened latency period for the development of brain cancer from cell phone radiation in children.

Q: The majority of industry-funded studies seem to show wireless radiation is safe. Yet the majority of independent studies show adverse effects. What research has investigated this?

A: With 87% of brain activity studies sponsored by the mobile phone industry, the issue of conflicts of interest cannot be ignored. The majority of telecom industry-sponsored research studies show no adverse effect and the majority of non-industry sponsored studies do show an adverse effect . Systematic reviews of the influence of financial interests in medical research have found strong associations between industry sponsorship and pro-industry conclusions ( Bekelman et al. 2003 ; Yaphe et al. 2001 ). Significant sponsorship and publication biases have been specifically noted in EMF research ( Huss 2007 , Valentini et al., 2011 ).

“We examined the methodologic quality and results of experimental studies investigating the effects of the type of radiofrequency radiation emitted by handheld cellular telephones. We hypothesized that studies would be less likely to show an effect of the exposure if funded by the telecommunications industry, which has a vested interest in portraying the use of mobile phones as safe. We found that the studies funded exclusively by industry were indeed substantially less likely to report statistically significant effects on a range of endpoints that may be relevant to health.”

“Conclusions: The interpretation of results from studies of health effects of radiofrequency radiation should take sponsorship into account.”

Harvard Press published an expose entitled Captured Agency outlining how conflict of interests are complicating science and policy. The book also details how scientists are dependent on industry for research funding because government funding for research on RF health effects has dried up.

Dr. Dariusz Leszczynski, was a member of a working group of 31 scientists from 14 countries constituted by the World Health Organization (WHO); which classified cell phone radiation as a group 2B carcinogen in 2011 and was working on research for which funding was promised by a Finnish organization Tekes, where about 70 percent funding for research is public money and rest comes from industry. He describes how industry stopped funding his research once effects were found and he is quoted as stating that, “When we found that cell phone effects human body the funding stopped because cell phone manufacturers Nokia and Teliasonnera said they didn’t like it. The scientific advisory board has industry partners as members. If industry partners think research will show a negative effect, it is often not funded by Tekes.”

In the 90’s researchers, Lai and Singh compared rats exposed to a low dose of microwave radiation finding a 30 percent increase in single-strand breaks in brain cell DNA compared to the control group. According to internal documents, Motorola started working behind the scenes to downplay the research. In a leaked Motorola memo and a draft position paper dated Dec. 13, 1994, Motorola talked about how they had “war-gamed the Lai-Singh issue” and were lining up “scientific” experts who would point out weaknesses in Lai’s study and reassure the public.

If you have any doubt about the power of industry to corrupt the science, simply step out of the EMF issue and look at how the lead industry , asbestos industry , and petroleum industry-funded science that minimized health effects and prolonged the inevitable.

For more expert analysis on industry influence into cell phone science please go here.

Q: What is a cell phone fine print warning?

A: Buried in cell phone manuals, cell phone companies specifically instruct us that phones should not be held close to the body. For example, the iPhone 5 manual states “Carry iPhone at least 10 mm away from your body to ensure exposure levels remain at or below the as tested levels. Cases with metal parts may change the RF performance of the device, including its compliance with RF exposure guidelines, in a manner that has not been tested or certified.”

The Blackberry Bold states, “keep the BlackBerry device at least 0.59 in. (15 mm) from your body (including the abdomen of pregnant women and the lower abdomen of teenagers) when the BlackBerry device is turned on and connected to the wireless network”.

Without following these instructions, we risk being exposed to levels of radiation that are too high- higher than radiation limits set by our federal government. The reality is that radiation emissions from devices are tested before going on the market- with a space between the device and your body. For cell phones, the distance varies depending on the manufacturer and is under an inch. For laptops, routers and baby monitor, the distance is about 8 inches. Did you know this?

Read Time Magazine’s article Cell-Phone Safety: What the FCC Didn’t Test FCC guidelines on the safety of cell phones assumed that there would be a buffer between the device and your body. Gulp
Read more about fine print instructions here.

Q: What other devices, besides cell phones, emit this type of radiation?

A: All devices that are wirelessly enabled will emit microwave radiation when the networks settings are on. These include DECT home cordless phones, the cordless home phone base, cordless baby monitors, Wi-Fi routers, wireless computers, gaming devices, iPads and tablets, wireless speakers, iPods that connect to the internet and even Fitbit.

If a device is wireless including Wi-Fi and Bluetooth), it is a two-way microwave radio and has microwave radiofrequency emissions. In the world we live in now people are exposed to microwave radiation from multiple devices in their home, school, and work every day. Federal regulations were developed decades ago before such scenarios could even be imagined. This is why we recommend reducing exposures and swapping out wireless with safe corded and wired connections whenever possible.

There is currently a huge push from school boards and local governments to make elementary schools entirely wireless. EHT has developed resources specifically on the issue of wireless exposures in schools .

Q: Do government regulations protect us?

A: Currently, government regulations for wireless radiation are outdated, irrelevant and non protective. They do not protect us from biological effects nor from long term cumulative exposures. For example, cell phone radiation levels are thousands of times lower than federal guidelines. Yet researchers are finding that these very low levels are not safe for the human body because research has found damaging effects even at these very low levels.

Remember that cell phone radiation is microwave radiation. Microwaves can cook food at high levels. They heat up food. At low levels (no cooking, non-heating) microwaves are used to send data between cell phones. Clearly we do not want to heat our body or brain. Government limits were set to protect us from heating only.

It is a fact that very very low level radiation from cell phones has biological effects. Take for example the U.S. National Institutes of Health research study that found that 50 minutes of exposure to cell phone radiation changed the energy metabolism in the human brain. The cell phone radiation actually increased the metabolism of glucose in the brain areas closest to the antenna. Dr. Nora D. Volkow, the brain imaging scientist who heads the National Institute on Drug Abuse and led this groundbreaking research stated (of this research that), “Even though the radio frequencies that are emitted from current cell phone technologies are very weak they are able to activate the human brain to have an effect.” Later, research on 3G and 4G has also shown that non-thermal (non-heating) levels of this radiation can alter the brain’s electrical activity.

Furthermore, federal guidelines are based on research that does not consider the special vulnerabilities of various population cohorts such as children or pregnant mothers. According to the Environmental Protection Agency (EPA), “Federal health and safety agencies have not yet developed policies concerning possible risk from long-term, non-thermal exposures.” This quote is from a Letter by Robert Hankin of the EPA’s Radiation Protection Division.

How can cell phones be safe if low levels alter brain activity? How can they be safe if there is significant research showing brain cancer in heavy cell phone users? What about research showing sperm damage and brain damage at levels of microwave radiation thousands of times lower than government regulations?

The reality is that most government regulations on allowable public exposures are set tens of thousands of times too high to protect the public.

Q: How did cell phones get on the market with so many problems?

A: In short, the industry was given a free pass decades ago that allow the exclusion of devices that emitted low levels of microwave radiation from proper safety testing. Cell phones and wireless devices are not safety tested like new drugs or medical devices are coming on the market. If a cell phone would have been tested like a drug, it would be taken off the market by now.

Several books have been written on the subject. Click here to see Dr. Devra Davis’s book Disconnect that details how the wireless industry “wargamed” the science. Click here to hear the history from expert scientist Dr. George Carlo of how the industry was able to get this technology to market before it was properly tested and how research findings have been suppressed since. His book Cell Phones: Invisible Hazards in a Wireless Age details industry corruption and how research has been suppressed. Dr. Carlo chaired $28 million dollars in research with the wireless industry. When his research found troubling effects, the wireless industry treated it like a public relations problem rather than a public health problem.

Q: What is a safe level of cell phone radiation?

A: Research has not yet identified a “safe level” of cell phone or wireless radiation. The United States provides us with an example of a common problem. Their expert scientific federal regulatory agencies the Food and Drug Administration (FDA) and Environmental Protection Agency (EPA) did not do pre-market safety testing nor did they perform research to determine a safe level of cell phone and wireless Radiation.

Instead, they adopted guidelines put out by wireless industry-led groups.

Although we do not know what a safe level of this radiation is at this time, we do know that even extremely low levels can have serious effects in research studies. We know that intensity is not the only factor to be concerned about because effects can depend on other characteristics of the technology- such as modulation.

Q: What should governments do?

A: The government needs to immediately reduce wireless exposures to the public and create awareness about the risks of cell phones and wireless devices. 5G and 4G densification should be halted.

Several national authorities have taken steps in this direction but a highly engaged public is critical to sustain these efforts.

The Canadian Parliament issued an excellent example of government recommendations. In 2015 which include updating guidelines, introducing policy measures to reduce exposure and educating the public.India has major research underway and has recommended limiting personal exposures. Israel has a National Institute for Non-Ionizing Radiation Safety.

Watch a video of Dr. R.S. Sharma, top Indian government scientists discuss the precautionary policies that the Indian government is taking such as educating consumers on safer ways to use cell phones, lowering the allowable RF emissions from cell towers and funding critical research at our lecture series at George Washington University.

Governments can start looking at the larger cost/benefit picture and the high monetary costs they could incur without immediate action. Consider that we now know the financial cost from lead poisoning is estimated at over 43 Billion per year. Now is the time to act.

Nobody can tell us the full cost of the health damages from wireless. However scientists are cautioning that it could be unprecedented. “Given that treatment for a single case of brain cancer can cost between $100,000 for radiation therapy alone and up to $1 million depending on drug costs, resources to address this illness are already in short supply and not universally available in either developing or developed countries. Significant additional shortages in oncology services are expected at the current growth of cancer. No other environmental carcinogen has produced evidence of an increased risk in just one decade.”

The growing body of evidence shows that there clearly are biological effects of prolonged exposure to wireless radiation. The government can use this information wisely to protect public health.

TEN YEAR REPORT

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Science News Explores

New study raises questions about cell phone safety, rat study offers support for world health organization conclusion that heavy cell phone use may cause cancer.

People love cell phones, which is why nine in 10 Americans own one. Many use them hours a day. So even a small cancer risk from their use — which has just been suggested by an animal study — could have important health implications.

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Newfound risks are small, but perplexing

NTP is part of the National Institute of Environmental Health Sciences. It’s in Research Triangle Park, N.C. Scientists at NTP study risks posed to people by things in the environment, such as radiation (X-rays, for instance) and chemicals (including bug killers, solvents and fire retardants).

Its new study found a small increase in cancer risk from cell-phone radiation. The scientists had exposed rats and mice to the same types of radiation emitted by U.S. cell phones. The findings that they released on May 26 come from rats. (NTP’s mouse data should emerge within the next 18 months.) The cancers in these rats resembled those seen in some human studies that had probed harm from cell phone use. For this reason, NTP says that its findings appear to support IARC’s conclusion that heavy cell-phone use might be harmful.

Still, “much work remains to be done to understand implications of these findings,” says John Bucher. He’s associate director of NTP. “The results are far from definitive,” he says. By that he means they could change, as more data come in.

The new findings do, however, raise important questions that warrant further study, says Bucher. For instance, he notes that the brain tumors that emerged in the rats are not a common type. Yet they are the type seen in some studies of human cell-phone users. They even occurred in the same part of the brain as did those that showed up in people.

NTP decided, last month, to share its early findings because cell phone use has become a basic feature of modern life. Nine out of 10 Americans own a cell phone. Nearly eight out of every 10 U.S. teens have or use a cell phone, as do more than half of all kids age 8 to 12 years old. So even a very small increase in harm from cell phone use could pose some threat to most people, NTP argues.

A big, complex study

NTP’s new cell-phone probe involved more than 7,000 animals. (That includes the work with mice, which will be reported next year.) This research took two years and cost $25 million. “These have been some of the most technically challenging studies we’ve ever attempted,” Bucher says.

The studies exposed animals to two types of radio waves. Each type is used in one of the two major radio systems that broadcast cell-phone signals. One system is known as the CDMA (for Code Division Multiple Access). In the United States, it’s used by many cell-phone networks, including Sprint and Verizon. The other is known as GSM (for Global System for Mobile communications). GSM radio frequencies are used throughout much of the world. They include some U.S. carriers, too, such as AT&T and T-Mobile. NTP used both RF types to see if their effects might differ.

The researchers exposed groups of 90 female rats and 90 male rats to three different levels of RF radiation. For more than 9 hours each day, the RF signals cycled on and off. They would be on for 10 minutes, then off for 10 minutes. Then the cycle repeated.

Exposures started just before a mother rat gave birth. Once her pups were born, their exposures would continue for another two years. Separate groups of 90 male and 90 female rats — known as the controls — were exposed to no radiation at all. In all, the rat study involved 1,260 animals. And by the time the study had ended, each rat was equivalent in age to a 60-year-old human.

The animals’ exposures differed in major ways from what people would experience. First, people do not talk on the phone all day long — from the womb through old age — for 10 out of every 20 minutes. Second, the animals’ whole bodies were exposed to the radio waves, not just their heads. Doses also were higher and more extensive than any human would encounter. However, none were high enough to heat the rats’ bodies nor to affect their growth.

Roughly 2 to 3 percent of male rats exposed to the RF radiation developed certain types of brain cancers. Rats in the control group developed none. In addition, between 2 and 6.6 percent of the exposed males developed potentially cancerous heart lesions . (Lesions are areas of damaged tissue.) Again, the control animals did not.

But the number of animals used in these tests was not large, notes Michael Lauer. He works at the National Institutes of Health in Bethesda, Md. This heart doctor is its deputy director for research that NIH funds in labs elsewhere. Says Lauer, the small number of animals used in the RF tests can make it hard to home in on why an unusual number of them developed cancer.

For now, because more of the rats developed heart lesions, the NTP scientists find this apparent risk from cell phones more compelling. A few female animals got cancer, but not more than tends to occur in any large group of rats. For that reason, the scientists see no measurable cell-phone cancer risk in these rats.

Curiously, rats in the control group were about twice as likely to have died (from a range of other causes) as were the rats exposed to RF radiation.

What might this mean for people?

Bucher says the new findings don’t necessarily mean that people should use cell phones less. It’s simply too early to know what to make of the new findings, he stresses.

But the U.S. Food and Drug Administration, or FDA, does have guidelines for safe cell-phone use. (FDA had asked NTP to look into health effects of cell phone radiation.) In guidelines issued 18 months ago, FDA said: “If there is a risk from being exposed to [RF] energy from cell phones — and at this point we do not know that there is — it is probably very small.” But, it added, people worried about health risks might choose to reduce their overall RF exposure. Anyone can do that, FDA points out, by using a headset or a phone’s speaker option. That way, the phone isn’t held next to the head.

New data, such as the NTP findings, may now prompt some “tweaks” to FDA’s recommendations, Bucher says.

Christopher Portier is more cautious about RF risks. He helped launch the new study when he was NTP’s associate director. (He now works for the Environmental Defense Fund, a nonprofit group that focuses on the environment.) Portier is most concerned about children’s use of devices that emit RF radiation.

Most people who are now adults grew up before cell phones were common, he notes. But children now use these phones as much as — or more than — adults. So “Children would be experiencing exposure for a much longer portion of their lifetimes,” he argues. Given that fact, along with new study’s data, “We should look carefully at children’s use of these devices,” he says.

He, too, pointed to advice (such as FDA’s) on how to limit exposure to cell phone radiation. “Distance is your friend,” Portier says. As with any type of radiation, he notes, the dose falls with distance. So, he says, don’t carry the phone on your body. And, he adds, “Keep the phone away from your head as much as possible.”

Big questions remain

If cell phones are dangerous, why aren’t U.S. brain cancer rates increasing? It’s an important question. But one for which there are no answers. It’s also unclear why female rats in the NTP study showed no increased risk of cancer.

Researchers do not yet know how long it might take for the type of tumors seen in the study’s rats to develop in people. It can take a decade or longer after exposure to some cancer-causing agents before tumors emerge. For now, Bucher notes, “It’s very reassuring that there is no dramatic increase” in brain cancer rates in people. “It may well be that current cell phone use is safe,” he says.

That’s the view of the Cellular Telecommunications Industry Association. CTIA represents the companies that make and service mobile phones. It said that many health groups “have determined that the already existing body of peer-reviewed and published studies shows that there are no established health effects” from cell phones. By peer review, CTIA is referring to studies that have been reviewed and challenged by scientists who were not involved in the research.

“Call phone use has increased dramatically over the last 30 years, from virtually zero to now most people,” notes the NIH’s Lauer. “And yet,” he notes, “we have not seen any marked increase in the rate of brain cancers.” But he adds: “Science is incremental,” meaning it advances in small steps. So a study like this one must be considered along with others when investigating risks. As a scientist, he argues, it’s unwise to conclude that cell phones are dangerous — or are not — based on one limited study.

FDA is now reviewing the new study’s findings to decide if its earlier conclusions about cell phone risks should be changed. In a May 27 statement, FDA noted that earlier studies “have not linked cell phones with any health problems.” But for people who are concerned, FDA points to an easy way to cut any risks: Spend less time on the phone.

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Cell Phones and Cancer Risk

Why has there been concern that cell phones may cause cancer.

There are two main reasons why people are concerned that cell (or mobile) phones might have the potential to cause certain types of cancer or other health problems: Cell phones emit radiation (in the form of radiofrequency radiation , or radio waves ), and cell phone use is widespread. Even a small increase in cancer risk from cell phones would be of concern given how many people use them.

Brain and central nervous system cancers have been of particular concern because hand-held phones are used close to the head and because ionizing radiation—a higher energy form of radiation than what cell phones emit—has been found to cause some brain cancers. Many different kinds of studies have been carried out to try to investigate whether cell phone use is dangerous to human health.

However, the evidence to date suggests that cell phone use does not cause brain or other kinds of cancer in humans.

Is the radiation from cell phones harmful?

Cell phones emit radiation in the radiofrequency region of the electromagnetic spectrum . Second-, third-, and fourth-generation cell phones (2G, 3G, 4G) emit radiofrequency in the frequency range of 0.7–2.7 GHz. Fifth-generation (5G) cell phones are anticipated to use the frequency spectrum up to 80 GHz.

These frequencies all fall in the nonionizing range of the spectrum, which is low frequency and low energy. The energy is too low to damage DNA. By contrast, ionizing radiation , which includes x-rays , radon , and cosmic rays, is high frequency and high energy. Energy from ionizing radiation can damage DNA. DNA damage can cause changes to genes that may increase the risk of cancer.

The NCI fact sheet Electromagnetic Fields and Cancer lists sources of radiofrequency radiation . More information about ionizing radiation can be found on the Radiation page.

The human body does absorb energy from devices that emit radiofrequency radiation. The only consistently recognized biological effect of radiofrequency radiation absorption in humans that the general public might encounter is heating to the area of the body where a cell phone is held (e.g., the ear and head). However, that heating is not sufficient to measurably increase core body temperature. There are no other clearly established dangerous health effects on the human body from radiofrequency radiation.

Has the incidence of brain and central nervous system cancers changed during the time cell phone use increased?

No. Investigators have studied whether the incidence of brain or other central nervous system cancers (that is, the number of new cases of these cancers diagnosed each year) has changed during the time that cell phone use increased dramatically. These studies found:

stable incidence rates for adult gliomas in the United States ( 1 ), Nordic countries ( 2 ) and Australia ( 3 ) during the past several decades
stable incidence rates for pediatric brain tumors in the United States during 1993–2013 ( 4 )
stable incidence rates for acoustic neuroma ( 5 ), which are nonmalignant tumors , and meningioma ( 6 ), which are usually nonmalignant, among US adults since 2009

In addition, studies using cancer incidence data have tested different scenarios (simulations) determining whether the incidence trends are in line with various levels of risk as reported in studies of cell phone use and brain tumors between 1979 and 2008 ( 7 , 8 ). These simulations showed that many risk changes reported in case-control studies were not consistent with incidence data, implying that biases and errors in the study may have distorted the findings.

Because these studies examine cancer incidence trends over time in populations rather than comparing risk in people who do and don’t use cell phones, their ability to observe potential small differences in risk among heavy users or susceptible populations is limited. Observational/epidemiologic studies—including case–control and cohort studies (described below)—are designed to measure individual exposure to cell phone radiation and ascertain specific health outcomes.

How is radiofrequency radiation exposure measured in studies of groups of people?

Epidemiologic studies use information from several sources, including questionnaires and data from cell phone service providers, to estimate radiofrequency radiation exposure in groups of people. Direct measurements are not yet possible outside of a laboratory setting. Estimates from studies reported to date take into account the following:

How regularly study participants use cell phones (the 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

What has research shown about the link between cell phone use and cancer risk?

Researchers have carried out several types of population studies to investigate the possibility of a relationship between cell phone use and the risk of tumors, both malignant (cancerous) and nonmalignant (not cancer). Epidemiologic studies (also called observational studies ) are research studies in which investigators observe groups of individuals (populations) and collect information about them but do not try to change anything about the groups.

Two main types of epidemiologic studies— cohort studies and case-control studies —have been used to examine associations between cell phone use and cancer risk. In a case–control study, cell phone use is compared between people who have tumors and people who don’t. In a cohort study, a large group of people who do not have cancer at the beginning of the study is followed over time and tumor development in people who did and didn’t use cell phones is compared. Cohort studies are limited by the fact that they may only be able to look at cell phone subscribers, who are not necessarily the cell phone users.

The tumors that have been investigated in epidemiologic studies include malignant brain tumors, such as gliomas , as well as nonmalignant tumors, such as acoustic neuroma (tumors in the cells of the nerve responsible for hearing that are also known as vestibular schwannomas), meningiomas (usually nonmalignant tumors in the membranes that cover and protect the brain and spinal cord ), parotid gland tumors (tumors in the salivary glands ), skin cancer, and thyroid gland tumors.

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. These studies have been critically evaluated in reviews reported in 2015 ( 9 ) and in 2019 ( 10 ). The findings of these studies are mixed, but overall, they do not show an association between cell phone use and cancer ( 11 – 22 ).

Interphone Case–Control Study

How the study was done: This is the largest 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 in Europe, Israel, Canada, Australia, New Zealand, and Japan.

What the study showed: Most published analyses from this study have shown no increases overall in brain or other central nervous system cancers (glioma and meningioma) related to higher amounts of cell phone use. One analysis showed a statistically significant , although small, increase in the risk of glioma among study participants who spent the most total time on cell phone calls. However, for a variety of reasons the researchers considered this finding inconclusive ( 11 – 13 ).

An analysis of data from all 13 countries reported a statistically significant association between intracranial distribution of tumors within the brain and self-reported location of the phone ( 14 ). However, the authors of this study noted that it is not possible to draw firm conclusions about cause and effect based on their findings.

An analysis of data from five Northern European countries showed an increased risk of acoustic neuroma in those who had used a cell phone for 10 or more years ( 15 ).

In subsequent analyses of Interphone data, investigators investigated whether tumors were more likely to form in areas of the brain with the highest exposure. One analysis showed no relationship between tumor location and level of radiation ( 16 ). However, another found evidence that glioma and, to a lesser extent, meningioma were more likely to develop where exposure was highest ( 17 ).

Danish Cohort Study

How the study was done: This cohort study 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 ( 18 – 20 ).

Million Women Cohort 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 ( 21 ), it was not observed with additional years of follow-up of the cohort ( 22) .

Other Epidemiologic Studies

In addition to these three large studies, other, smaller epidemiologic studies have looked for associations between cell phone use and individual cancers in both adults and children. These include:

Two NCI-sponsored case–control studies, each conducted in multiple US academic medical centers or hospitals between 1994 and 1998 that used data from questionnaires ( 23 ) or computer-assisted personal interviews ( 24 ). Neither study showed a relationship between cell phone use and the risk of glioma, meningioma, or acoustic neuroma in adults.
The CERENAT study, another case–control study conducted in multiple areas in France from 2004 to 2006 using data collected in face-to-face interviews using standardized questionnaires ( 25 ). This study found no association for either gliomas or meningiomas when comparing adults who were regular cell phone users with non-users. However, the heaviest users had significantly increased risks of both gliomas and meningiomas.
A pooled analysis of two case–control studies conducted in Sweden that reported 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 ( 26 ).
Another case–control study in Sweden, part of the Interphone pooled studies, did not find an increased risk of brain cancer among long-term cell phone users between the ages of 20 and 69 ( 27 ).
The CEFALO study, an international case–control study of children diagnosed with brain cancer between ages 7 and 19, found no relationship between their cell phone use and risk for brain cancer ( 28 ).
The MOBI-Kids study, a large international case–control study of young people ages 10 to 24 years diagnosed with brain tumors, found no evidence of an association between wireless phone use and the risk of brain tumors ( 29 ).
A population-based case–control study conducted in Connecticut found no association between cell phone use and the risk of thyroid cancer ( 30 ).

What are the findings from studies of the human body?

Researchers have carried out several kinds of studies to investigate possible effects of cell phone use on the human body. In 2011, two small studies were published that examined brain glucose metabolism in people after they had used cell phones. The results were inconsistent. 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 ( 31 ); the other study ( 32 ) found reduced glucose metabolism on the side of the brain where the phone was used.

The authors of these studies noted that the results were preliminary and that possible health outcomes from changes in glucose metabolism in humans were unknown. Such inconsistent findings are not uncommon in experimental studies of the physiological effects of radiofrequency electromagnetic radiation in people ( 11 ). Some factors that can contribute to inconsistencies across such studies include assumptions used to estimate doses, failure to consider temperature effects, and investigators not being blinded to exposure status.

Another study investigated blood flow in the brain of people exposed to radiofrequency radiation from cell phones and found no evidence of an effect on blood flow in the brain ( 33 ).

What are the findings from experiments in laboratory animals?

Early studies involving laboratory animals showed no evidence that radiofrequency radiation increased cancer risk or enhanced the cancer-causing effects of known chemical carcinogens ( 34 – 37 ).

Because of inconsistent findings from epidemiologic studies in humans and the lack of clear data from previous experimental studies in animals, in 1999 the Food and Drug Administration (FDA) nominated radiofrequency radiation exposure associated with cell phone exposures for study in animal models by the US National Toxicology Program (NTP). NTP is an interagency program that coordinates toxicology research and testing across the US Department of Health and Human Services and is headquartered at the National Institute of Environmental Health Sciences, part of NIH.

The NTP studied radiofrequency radiation (2G and 3G frequencies) in rats and mice ( 38 , 39 ). This large project was conducted in highly specialized labs. The rodents experienced whole-body exposures of 3, 6, or 9 watts per kilogram of body weight for 5 or 7 days per week for 18 hours per day in cycles of 10 minutes on, 10 minutes off. A research overview of the rodent studies , with links to the peer-review summary, is available on the NTP website. The primary outcomes observed were a small number of cancers of Schwann cells in the heart and non-cancerous changes ( hyperplasia ) in the same tissues for male rats, but not female rats, nor in mice overall.

These experimental findings raise new questions because cancers in the heart are extremely rare in humans. Schwann cells of the heart in rodents are similar to the kind of cells in humans that give rise to acoustic neuromas (also known as vestibular schwannomas), which some studies have suggested are increased in people who reported the heaviest use of cell phones. The NTP plans to continue to study radiofrequency exposure in animal models to provide insights into the biological changes that might explain the outcomes observed in their study.

Another animal study, in which rats were exposed 7 days per week for 19 hours per day to radiofrequency radiation at 0.001, 0.03, and 0.1 watts per kilogram of body weight was reported by investigators at the Italian Ramazzini Institute ( 40 ). Among the rats with the highest exposure levels, the researchers noted an increase in heart schwannomas in male rats and nonmalignant Schwann cell growth in the heart in male and female rats. However, key details necessary for interpretation of the results were missing: exposure methods, other standard operating procedures, and nutritional/feeding aspects. The gaps in the report from the study raise questions that have not been resolved.

ICNIRP (an independent nonprofit organization that provides scientific advice and guidance on the health and environmental effects of nonionizing radiation) critically evaluated both studies. It concluded that both followed good laboratory practice, including using more animals than earlier research and exposing the animals to radiofrequency radiation throughout their lifetimes. However, it also identified what it considered major weaknesses in how the studies were conducted and statistically analyzed and concluded that these limitations prevent drawing conclusions about the ability of radiofrequency exposures to cause cancer ( 41 ).

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

A few studies have shown some evidence of statistical association of cell phone use and brain tumor risks in humans, but most studies have found no association. Reasons for these discrepancies include the following:

Recall bias , which can occur when data about prior habits and exposures are collected from study participants using questionnaires administered after diagnosis of a disease in some of the participants. Study participants who have brain tumors, for example, may remember their cell phone use differently from individuals without brain tumors.
Inaccurate reporting , which can happen when people say that something has happened more often or less often than it actually did. For example, 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 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.
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.
Changing technology. Older studies evaluated radiofrequency radiation exposure from analog cell phones. Today, cell phones use digital technology, which operates at a different frequency and a lower power level than analog phones, and cellular technology continues to change ( 42 ).
Exposure assessment limitations. Different studies measure exposure differently, which makes it difficult to compare the results of different studies ( 43 ). Investigations of sources and levels of exposure, particularly in children, are ongoing ( 44 ).
Insufficient follow-up of highly exposed populations. It may take a very long time to develop symptoms after exposure to radiofrequency radiation, and current studies may not yet have followed participants long enough.
Inadequate statistical power and methods to detect very small risks or risks that affect small subgroups of people specifically
Chance as an explanation of apparent effects may not have been considered.

What are other possible health effects from cell phone use?

The most consistent health risk associated with cell phone use is distracted driving and vehicle accidents ( 45 , 46 ). Several other potential health effects have been reported with cell phone use. Neurologic effects are of particular concern in young persons. However, studies of memory, learning, and cognitive function have generally produced inconsistent results ( 47 – 50 ).

What have expert organizations said about the cancer risk from cell phone use?

In 2011, the International Agency for Research on Cancer (IARC) , a component of the World Health Organization, appointed an expert working group to review all available evidence on the use of cell phones. The working group classified cell phone use as “possibly carcinogenic to humans,” based on limited evidence from human studies, limited evidence from studies of radiofrequency radiation and cancer in rodents, and inconsistent evidence from mechanistic studies ( 11 ).

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 variables rather than an underlying causal effect. In addition, the working group stated that the investigation of brain cancer risk associated with cell phone use poses complex research challenges.

The American Cancer Society’s cell phones page states “It is not clear at this time that RF (radiofrequency) waves from cell phones cause dangerous health effects in people, but studies now being done should give a clearer picture of the possible health effects in the future.”

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 US Food and Drug Administration (FDA) notes that studies reporting biological changes associated with radiofrequency radiation have failed to be replicated and that the majority of human epidemiologic studies have failed to show a relationship between exposure to radiofrequency radiation from cell phones and health problems. FDA, which originally nominated this exposure for review by the NTP in 1999, issued a statement on the draft NTP reports released in February 2018, saying “based on this current information, we believe the current safety limits for cell phones are acceptable for protecting the public health.” FDA and the Federal Communications Commission (FCC) share responsibility for regulating cell phone technologies.

The US 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 currently no scientific evidence establishes a definite 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 radiation exposure do not show an increased risk of brain tumors or of other cancers of the head and neck region ( 9 ). The committee also stated that epidemiologic studies do not indicate increased risk for other malignant diseases, including childhood cancer ( 9 ).

What studies of cell phone health effects are under way?

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 Cohort Study of Mobile Phone Use and Health (or COSMOS ), has enrolled approximately 290,000 cell phone users aged 18 years or older to date and will follow them for 20 to 30 years ( 51 , 52 ).

Participants in COSMOS completed a questionnaire about their health, lifestyle, and current and past cell phone use when they joined the study. This information will be supplemented with information from health records and cell phone records. Research updates are posted to the COSMOS website .

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, for example family members who may share a device, will be represented on a single phone company account. Additionally, for many long-term cohort studies, participation tends to decline over time.

Has radiofrequency radiation from cell phone use been associated with cancer risk in children?

There are theoretical considerations as to why the potential health effects of cell phone use 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 radiation emitted by cell phones. And, children have the potential of accumulating more years of cell phone exposure than adults.

Thus far, the data from studies of children with cancer do not suggest that children are at increased risk of developing cancer from cell phone use. The first published analysis came from a large case–control study called CEFALO, which was conducted in Europe. The study included 352 children who were diagnosed with brain tumors between 2004 and 2008 at the ages of 7 to 19 years. They were matched by age, sex, and geographical region with 646 young people randomly selected from population registries. Researchers did not find an association between cell phone use and brain tumor risk by amount of use or by the location of the tumor ( 28 ).

The largest case–control study among children, a 14-country study known as MOBI-Kids , included 899 young people ages 10 to 24 years who were diagnosed with brain tumors between 2010 and 2015. They were matched by sex, age, and region with 1,910 young people who were undergoing surgery for appendicitis. Researchers found no evidence of an association between wireless phone use and brain tumors in young people ( 29 ).

Which US federal agencies have a role in evaluating the effects of or regulating cell phones?

The National Institutes of Health (NIH), including the National Cancer Institute (NCI), conducts research on cell phone use and the risks of cancer and other diseases.

FDA and FCC share regulatory responsibilities for cell phones. FDA is responsible for testing and evaluating electronic product radiation and providing information for the public about the radiofrequency energy emitted by cell phones. FCC sets limits on the emissions of radiofrequency energy by cell phones and similar wireless products.

Where can I find more information about radiofrequency radiation from my cell phone?

The dose of the energy that people absorb from any source of radiation is estimated using a measure called the specific absorption rate (SAR), which is expressed in watts per kilogram of body weight ( 53 ). The SAR decreases very quickly as the distance to the exposure source increases. For cell phone users who hold their phones next to their head during voice calls, the highest exposure is to the brain, acoustic nerve, salivary gland, and thyroid.

The FCC provides information about the SAR of cell phones produced and marketed within the previous 1 to 2 years. 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 . SARs for older phones can be found by checking the phone settings or by contacting the manufacturer.

What can cell phone users do to reduce their exposure to radiofrequency radiation?

FDA has suggested some steps that concerned cell phone users can take to reduce their exposure to radiofrequency radiation ( 54 ):

Reserve the use of cell phones for shorter conversations or for times when a landline phone is not available.
Use a device with hands-free technology, such as wired headsets, which place more distance between the phone and the head of the user.

Use of wired or wireless headsets reduces the amount of radiofrequency radiation exposure to the head because the phone is not placed against the head ( 55 ). Exposures decline dramatically when cell phones are used hands-free.

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Infographics on Cell Phone Radiation, Wi-Fi and 5G
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